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Discovering Computers ©2016 Instructor’s Manual Page 1 of 18
© 2016 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.
Discovering Computers:
Tools, Apps, and the Impact of Technology ©2016
Chapter Three: Computers and Mobile Devices: Evaluating Options for
Home and Work
A Guide to this Instructor’s Manual:
We have designed this Instructor’s Manual to supplement and enhance your teaching experience through classroom
activities and a cohesive chapter summary.
This document is organized chronologically, using the same heading in red that you see in the textbook. Under each
heading you will find (in order): Lecture Notes that summarize the section, Figures and Boxes found in the section, if
any, Teacher Tips, Classroom Activities, and Lab Activities. Pay special attention to teaching tips, and activities geared
towards quizzing your students, enhancing their critical thinking skills, and encouraging experimentation within the
software.
In addition to this Instructor’s Manual, our Instructor’s Resources also contain PowerPoint Presentations, Test Banks,
and other supplements to aid in your teaching experience.
For your students:
Our latest online feature, CourseCasts, is a library of weekly podcasts designed to keep your students up to date with
the latest in technology news. Direct your students to http://coursecasts.course.com, where they can download the
most recent CourseCast onto their mp3 player. Ken Baldauf, host of CourseCasts, is a faculty member of the Florida
State University Computer Science Department where he is responsible for teaching technology classes to thousands of
FSU students each year. Ken is an expert in the latest technology and sorts through and aggregates the most pertinent
news and information for CourseCasts so your students can spend their time enjoying technology, rather than trying to
figure it out. Open or close your lecture with a discussion based on the latest CourseCast.
Table of Contents
Chapter Objectives
108: Computers and Mobile Devices
108: Mobile Computers and Desktops
116: Servers
117: Terminals
120: Supercomputers
121: Cloud Computing
122: Mobile Devices
131: Game Devices
132: Embedded Computers
134: Putting It All Together
134: Ports and Connections

139: Protecting Hardware
142: Health Concerns of Using Technology
End of Chapter Material
Glossary of Primary Terms
Glossary of Secondary Terms
Chapter Objectives
Students will have mastered the material in Chapter Three when they can:
⚫ Describe the characteristics and uses of
laptops, tablets, desktops, and all-in-ones
⚫ Describe the characteristics and types of
servers
⚫ Differentiate among POS terminals, ATMs,
and self-service kiosks
⚫ Describe cloud computing and identify its
uses
⚫ Describe the characteristics and uses of
smartphones, digital cameras, portable and
digital media players, e-book readers, and
wearable devices
⚫ Describe the characteristics of and ways to
interact with game devices, including
gamepads, joysticks and wheels, dance pads,
and motion-sensing controllers
⚫ Identify uses of embedded computers
⚫ Differentiate a port from a connector,
identify various ports and connectors, and
differentiate among Bluetooth, Wi-Fi, and
NFC wireless device connections
⚫ Identify safeguards against hardware theft
and vandalism and hardware failure
⚫ Discuss ways to prevent health-related
injuries and disorders caused from
technology use, and describe ways to design
a workplace ergonomically
108: Computers and Mobile Devices
LECTURE NOTES
• Use Figure 3-1 to recall the definitions of computer and mobile device from Chapter 1
• Discuss the aspects of computers and mobile devices to be reviewed in this chapter, from their
features, functions, and purchasing guidelines to the connection of peripheral devices,
protection against theft and failure, and the minimizing of health risks during their use
FIGURES and TABLES: Figure — 3-1
BOXES
1. BTW: Peripheral Devices. Offer the definition (and examples of) peripheral devices and remind
students that additional information is available on this subject.
CLASSROOM ACTIVITIES
1. Class Discussion: Every student is aware of, and most students probably are very comfortable with,
computers and mobile devices. Throughout this chapter, encourage students to share their experiences
with the kinds of computers and mobile devices described in the text.

2. Quick Quiz:
1) What is a computer? (Answer: an electronic device, operating under the control of instructions
stored in its own memory, that can accept data (input), process the data according to specified
rules, produce information (output), and store the information for future use)
2) What is a mobile device? (Answer: a computing device small enough to hold in your hand)
3. Critical Thinking: What are some of the essential aspects of the daily lives of your students that are
made possible by computers and mobile devices?
108: Mobile Computers and Desktops
LECTURE NOTES
• Define personal computer
• Review some of the operating systems used by personal computers
• Define mobile computer
• Use Figure 3-2 to review the components of a personal computer
• Use Figure 3-3 to explain the differences between traditional and ultrathin laptop computers and
include the term notebook computer in your discussion
• Use Figure 3-4 to explain the differences between slate and convertible tablets
• Use Figure 3-5 to explain what a phablet is
• Use Figure 3-6 to explain what a handheld computer is and how it is used
• Use Figure 3-7 to explain the components of desktops and all-in-one computers
FIGURES and TABLES: Figures — 3-2, 3-3, 3-4, 3-5, 3-6, 3-7
BOXES
1. BTW: Discuss the term PC and how this term is used.
2. Secure IT 3-1: Avoid Malware Infections. Discuss in detail the guidelines that students should follow
to avoid malware infections on their computers and mobile devices, when visiting websites, using social
media and email, and the like.
3. Consider This: What is inside a personal computer? Discuss the electronic components of a personal
computer and include definitions of motherboard, processor (or CPU), and memory in your discussion.
4. Internet Research: What is a computer chip? Encourage students to experiment with using the
following search terms in their favorite search engine: computer chip.
5. BTW: Technology Innovator. Invite students to make sure they are familiar with Samsung and
remind students that additional information is available on this subject.
6. Ethics and Issues 3-1: What Punishment for Webcam Spying Is Appropriate? Discuss the use of
webcams and other similar technology for spying, and encourage students to engage in this debate, from
the perspective of both an individual and a corporate entity, like Google with regard to the Google
Street View product.

7. BTW: Ultrabooks. Define ultrabook and remind students that additional information is available on
this subject.
8. BTW: Pens. Discuss the pens used by some devices and remind students that additional information is
available on this subject.
9. Consider This: What is a phablet? Use Figure 3-5 to explain what a phablet is.
10. Mini Feature 3-1: Mobile Computer Buyer’s Guide. Review the considerations for the purchase of a
mobile computer.
11. BTW: Monitor Speakers. Discuss the integration of speakers into computer monitors, and remind
students that additional information is available on this subject.
12. BTW: Dell. Discuss Dell and its founder Michael Dell and remind students that additional
information is available on this subject.
13. Consider This: Who uses desktops? Review some of the professions that continue to make use of
desktops for a variety of different reasons and purposes. Define gaming desktop and workstation.14.
Internet Research: Which movies use computer animation? Encourage students to experiment with
using the following search terms in their favorite search engine: movies using computer animation.
15. BTW: High-Tech Talk. Discuss how touch screens use capacitive, resistive, surface wave, and other
technologies to sense touch and remind students that additional information is available on this subject.
16. Mini Feature 3-2: Desktop Buyer’s Guide. Review the considerations for the purchase of a desktop
computer.
1. Class Discussion: Ask students about their experience with handheld computers as described in the
text. What industries or experiences have particularly benefited from the advent of handheld
computers? What activities could not be done without them?
2. Assign a Project: Ask students to research phablets online. For what purposes are they particularly
suited?
3. Quick Quiz:
1) To what does the system unit refer in a desktop? (Answer: the case that contains and protects
the motherboard, hard disk drive, memory, and other electronic components of the computer
from damage)
2) The term form factor refers to the resolution of a computer monitor. True or false? (Answer:
False)
3) What is an all-in-one desktop? (Answer: a desktop without a tower that instead houses the
screen and system unit in the same case)
4) A slate tablet contains a phy
5) sical keyboard. True or false? (Answer: False)

4. Critical Thinking: Though desktops once dominated the computer market, the advent of laptops and
mobile devices have changed the game. Beyond the examples provided in the text, under what
circumstances (either professional or personal) do desktops remain the computer of choice?
LAB ACTIVITIES
1. Assign students the task of researching the purchase of a desktop computer using the guidelines in
the text and ask them to report on their recommendations. As an additional component of this activity,
give them a specific professional role (e.g., game developer, multimedia designer) and ask them to factor
the requirements of that role into their research and their ultimate recommendation.
2. Assign students the task of researching the purchase of a mobile computer using the guidelines in the
text and ask them to report on their recommendations. As an additional component of this activity, give
them a specific professional role (e.g., salesperson) and ask them to factor the requirements of that role
into their research and their ultimate recommendation.
116: Servers
LECTURE NOTES
• Define server
• Discuss the variety of services provided by servers
• Use Table 3-1 to review the range of dedicated servers available to perform a variety of different
functions
• Define the following servers: application, backup, database, domain name, file, FTP, game, home,
list, mail, network, print, and web
• Use Figure 3-8 to review the different server form factors: rack, blade, and tower
• Define virtualization and server virtualization
• Use Figure 3-9 to explain what a server farm is
• Define mainframe
FIGURES and TABLES: Figures — 3-8, 3-9; Table — 3-1
BOXES
1. Consider This: Which server should you use? Review the examples of form factors in the text in
terms of which is the best match for a given situation.
TEACHER TIPS
Server virtualization is an interesting development in information technology which may be of interest
to students. Some industry observers offer that server virtualization has become popular in part because
the IT industry has had to shift from deploying new services and applications to focusing instead on
managing existing infrastructure and that as a result, the rate of innovation for new capabilities and
software has slowed down. To compensate for this, many organizations are using virtualization to
radically simplify the administration of their existing servers. This takes the form of reducing
operational overhead in staffing, power, backup, hardware, and software maintenance.

1. Class Discussion: The growing movement toward decentralization in business, coupled with the
increasing power of servers, has led to a recent trend away from mainframe computers and toward
servers. Ask students what advantages servers might have over larger computers, such as mainframes,
for a business.
2. Class Discussion: As cloud computing gets more popular, this phenomenon has had one unintended
consequence. The Environmental Protection Agency notes that the nation's data centers are consuming
more than 100 billion kilowatt-hours, which costs more than $7 billion each year—a rate that is double
what they consumed six years ago. Discuss with students the implications of this phenomenon in terms
of green computing.
3. Group Activity: Present students with a variety of examples of corporate situations and ask students
to suggest which form factor of server would be optimal for those situations.
4. Group Activity: If the school has a server or mainframe in a central computing center, arrange for a
guided tour.
5. Quick Quiz:
1) Which of the following is a server housed in a slot on a metal frame? (a) rack (b) blade (c) tower
(d) virtual (Answer: a)
2) Cloud computing uses server virtualization. True or false? (Answer: True)
3) What is virtualization? (Answer: the practice of sharing or pooling computing resources, such as
servers or storage devices)
4) A tower server is a server in the form of a single circuit board. True or false? (Answer: False)
117: Terminals
LECTURE NOTES
• Define terminal and thin client
• Use Figure 3-10 to define POS terminal
• Explain what a bar code reader is
• Explain what it means for a POS terminal to be Internet capable
• Use Figure 3-11 to define ATM and PIN
• Use Figure 3-12 to define kiosk and use Table 3-2 to review some of the functions of self-service
kiosks (in particular DVD kiosks, as shown in this figure)
FIGURES and TABLES: Figures — 3-10, 3-11, 3-12; Table — 3-2
BOXES
1. BTW: Technology Trend. Discuss Bitcoin as a digital currency and remind students that additional
information is available on this subject.
2. Secure IT 3-2: ATM Safety. Review all these guidelines for keeping students from being the victims of
criminal activity regarding their usage of ATMs. Define the term skimmer.

3. Internet Research: What is a mobile boarding pass? Encourage students to experiment with using the
following search terms in their favorite search engine: mobile boarding pass.
1. Now You Should Know: Have students visit this chapter’s premium content for practice quiz
opportunities.
120: Supercomputers
LECTURE NOTES
• Use Figure 3-13 to define supercomputer
• Review some of the applications of supercomputing technology
BOXES
1. Internet Research: How is the fastest supercomputer used? Encourage students to experiment with
using the following search terms in their favorite search engine: fastest supercomputer.
2. Now You Should Know: Be sure students understand the material in Computers and Mobile Devices,
Mobile Computers and Desktops, Servers, Terminals, and Supercomputers sections, and how it relates to
the chapter objectives listed. Encourage students to discover more using the chapter’s premium content
and practice quizzes.
1. Assign a Project: What is the origin of the universe? It is a big question and supercomputers are
making it possible to note what went on during the universe's birth, 13 billion years ago in trillion-
degree Celsius temperatures during the Big Bang. Researchers at the University of Texas in Austin have
used supercomputers to simulate the creation of the first galaxy, and NASA scientists have simulated the
creation of stars from cosmic dust and gas. In addition to solving cosmic mysteries like these,
supercomputers have many other applications. Encourage students to use their favorite search engine to
research another interesting use of supercomputing technology and write a brief recap of their findings.
2. Quick Quiz:
1) What is a supercomputer? (Answer: the fastest, most powerful computer, and the most
expensive)
121: Cloud Computing
LECTURE NOTES
• Use Figure 3-14 to define cloud computing
BOXES
1. BTW: The Cloud. Discuss the common graphical representation of the cloud and remind students
that additional information is available on this subject.

2. Internet Research: How secure is the cloud? Encourage students to experiment with using the
following search terms in their favorite search engine: cloud privacy issues.
3. Consider This: Are all cloud services available to everyone? Differentiate between public clouds and
private clouds, and mention that some cloud services are hybrid.
TEACHER TIP
Students interested in cloud computing may be interested in one of the most important related
developments: software as a service (SaaS). In software as a service, computer applications are accessed
over the Internet instead of being installed on a local computing device or in a local data center.
Examples include the use of an online word processor like Google Docs. The benefits of SaaS include
the dynamic scalability and device independence, along with the ability to use an application without
fixed costs. Many SaaS applications are also collaborative, which empowers multiple users to work on
shared documents at the same time. All of these benefits herald a significant new direction in software
engineering — and opportunities.
1. Quick Quiz:
1) To what does cloud computing refer? (Answer: an environment of servers that house and
provide access to resources users access through the Internet)
2) Businesses use cloud computing to more efficiently use resources, such as servers and programs,
by shifting usage and consumption of these resources from a local environment to the Internet.
True or false? (Answer: True)
2. Critical Thinking: Apple co-founder Steve Wozniak has been quoted as saying: “With the cloud, you
don’t own anything. You already signed it away” (regarding the terms of service with a cloud provider
to which computer users must agree). “I want to feel that I own things. A lot of people feel, ‘Oh,
everything is really on my computer,’ but I say the more we transfer everything onto the [W]eb, onto
the cloud, the less we’re going to have control over it.” Ask students to debate this view, and to consider
the consequences of their point of view.
122: Mobile Devices
LECTURE NOTES
• Remind students of the definition of a mobile device
• Use Figure 3-15 to define smartphone and review the features that many typing options
smartphones have, in addition to conventional phone capabilities
• Explain what an on-screen keyboard is and discuss swipe keyboard app, portable keyboard and
virtual keyboard
• Define predictive text
• Explain what text message service (or SMS, or short message service) is and review the options for
text message services
• Define common short code (CSC)
• Explain what picture/video message service (or MMS, or multimedia message service) is and review
the options for picture/video message services
• Explain what voice mail and visual voice mail are

• Provide the definition of a digital camera and distinguish a point-and-shoot camera from an SLR
camera using Figure 3-16
• Use Figure 3-17 to review the way in which a digital camera works
• Define resolution and charge-coupled device (CCD)
• Use Figure 3-18 to define pixel
• Define optical resolution and enhanced resolution
• Use Figure 3-19 to provide the definition of a portable media player
• Explain what earbuds and a touch-sensitive pad are
• Define media library
• Use Figure 3-20 to provide the definition of a digital media player (streaming media player)
• Use Figure 3-21 to provide the definition of an e-book reader (e-reader)
• Use Figure 3-22 to define wearable devices and discuss the types of wearable devices, including
activity trackers, smartwatches, and smartglasses (smart eyewear)
FIGURES and TABLES: Figures — 3-15, 3-16, 3-17, 3-18, 3-19, 3-20, 3-21, 3-22
BOXES
1. Ethics and Issues 3-2: Should Recycling of Electronics Be Made Easier? Encourage students to engage
in this debate — and also to share their own ideas about what might reduce e-waste and promote
recycling.
2. BTW: High-Tech Talk. Encourage students to familiarize themselves with voice recognition
technology and remind students that additional information is available on this subject.
3. Consider This: How do you type text messages on a phone that has only a numeric keypad and no
touch screen? Survey students about their experience — and facility — with a keypad like the one
described in the text.
4. Consider This: What is the difference between push and pull notifications? Survey students about
their experience with push and pull notifications.
5. Internet Research: What messaging apps are recommended? Encourage students to experiment with
using the following search terms in their favorite search engine: best messaging apps.
6. Consider This: Do you need a messaging service to send a text or picture/video message? Survey
students about their experience with mobile messaging apps and ask them to discuss their capabilities
and cost.
7. BTW: Analog vs. Digital. Offer definitions of analog and digital technology, contrasting the two, and
8. Secure IT 3-3: Safe Mobile Device Use in Public Areas. Review the suggestions for keeping students
from being the victims of criminal activity regarding their usage of mobile devices.

9. Consider This: Do you need a digital camera if you have a camera built into your mobile phone?
Survey students about their experience using the camera in their mobile phone and ask them to debate
its strengths and limitations.
10. Internet Research: What is an SD card? Encourage students to experiment with using the following
search terms in their favorite search engine: sd card information.
11. BTW: Sony. Encourage students to familiarize themselves with Sony and remind students that
additional information is available on this subject.
12. BTW: EarPods. Provide the definition of EarPods and remind students that additional information is
available on this subject.
13. Mini Feature 3-3: Mobile Device Buyer’s Guide. Review the considerations for the purchase of a
smartphone, digital camera, or portable media player.
14. BTW: Electronic Paper Screen. Ask students to consider their own preferences (black-and-white
screens versus color) and remind students that additional information is available on this subject.
15. Consider This: Do you need a separate e-book reader if you have a tablet or other device that can
function as an e-book reader? Survey students about their experience using a tablet (or even a
smartphone) as an e-book reader and ask them to debate its strengths and limitations.
16. Internet Research: Which activity trackers are the most widely used? Encourage students to
experiment with using the following search terms in their favorite search engine: popular activity
trackers.
17. Internet Research: How does augmented reality apply to smartglasses? Encourage students to
experiment with using the following search terms in their favorite search engine: augmented reality.
1. Quick Quiz:
1) With predictive text input, you press keys on the screen using your fingertip or a stylus. True or
false? (Answer: False)
2) With SMS, messages are typically fewer than 300 characters. True or false? (Answer: True)
3) Approximately what percent of e-waste is recycled? (Answer: 20)
4) Which is more expensive, a point-and-shoot camera or an SLR camera? (Answer: an SLR
camera)
5) When does inattentional blindness occur? (Answer: when a person’s attention is diverted while
performing a natural activity, such as walking)
6) What is optical resolution? (Answer: the actual resolution at which a photograph is taken)
131: Game Devices
LECTURE NOTES
• Define game console
• Explain what a handheld game device is

• Use Figure 3-23 to discuss the following options for directing movements and actions of on-screen
objects: gamepad, joystick, pedals and wheel, dance pad, motion-sensing game controllers, and
balance board
BOXES
1. BTW: Nintendo. Encourage students to familiarize themselves with Nintendo and remind students
2. Internet Research: Which video games are the most widely used? Encourage students to experiment
with using the following search terms in their favorite search engine: popular video games.
3. Ethics and Issues 3-3: Are Fitness Video Games and Apps Qualified to Provide Medical Advice?
Encourage students to engage in this debate — and also to share their own ideas about what the
appropriate role of video games and smartphone apps are in terms of providing information about
workout routines and other fitness information. Survey students about their experience with these
resources.
1. Quick Quiz:
1) What is a game console? (Answer: a mobile computing device designed for single-player or
multiplayer video games)
2) A gamepad is a flat, electronic device divided into panels that users press with their feet in
response to instructions from a music video game. True or false? (Answer: False)
132: Embedded Computers
LECTURE NOTES
• Define embedded computer
• Review the everyday products that make use of embedded computing technology
Discuss Figure 3-24 and the various embedded computers designed to improve safety, security and
performance in today’s vehicles
BOXES
1. Ethics and Issues 3-4: Does In-Vehicle Technology Foster a False Sense of Security? Encourage
students to engage in this debate — and also to share their own experiences with technologies as
described in the text (and perhaps also operating vehicles without the benefit of these technologies).
2. Consider This: Can embedded computers use the Internet to communicate with other computers and
devices? Using Smart TV technology — as well as the Internet of Things described in the text — discuss
the phenomenon of M2M communications.
1. Assign a Project: Encourage students to read more about the Internet of Things online and to write a

brief recap of their findings.
2. Quick Quiz:
1) What is an embedded computer? (Answer: a special-purpose computer that functions as a
component in a larger product)
134: Putting It All Together
LECTURE NOTES
• Use Table 3-3 to review the categories of computers and mobile devices discussed to this point
FIGURES and TABLES: Table — 3-3
BOXES
1. BTW: Technology Trend. Discuss with students the concept of donating computer resources to
worthy scientific research, for example, and remind students that additional information is available on
this subject.
2. Now You Should Know: Be sure students understand the material in Cloud Computing, Mobile
Devices, Game Devices, Embedded Computers, and Putting It All Together sections, and how it relates
to the chapter objectives listed. Encourage students to discover more using the chapter’s premium
content and practice quizzes.
opportunities.
LAB ACTIVITIES
1. As a possible assignment, ask students to research volunteer computing opportunities (potentially in
an area of interest to them) using their favorite search engine. SETI@home is one famous example, but
there are many options, including in research related to cancer, climate change, and HIV/AIDS.
134: Ports and Connections
LECTURE NOTES
• Use Figure 3-25 to define port
• Define connector and use Table 3-4 to review the popular types of ports and connectors found in
computers and mobile devices today
• Explain the function of a USB port
• Define backward compatible and explain the function of a USB hub
• Explain what a port replicator is
• Use Figure 3-26 to define docking station
• Introduce the wireless communications technologies of Bluetooth, Wi-Fi, and NFC
• Discuss the range limitations of Bluetooth technology
• Explain the function of a Bluetooth wireless port adapter
• Define Wi-Fi and discuss the range implications for Wi-Fi technology

• Define NFC (near field communications) and discuss the objects and devices that take advantage of
this technology
FIGURES and TABLES: Figures — 3-25, 3-26; Table — 3-4
BOXES
1. BTW: Encourage students to familiarize themselves with jack, the alternative to the term port, and
2. Secure IT 3-4: Public USB Charging Stations – Safe or Not? Review the suggestions for keeping
students from being the victims of criminal activity regarding their usage of charging kisosks and
stations.
3. How To 3-1: Pair Bluetooth Devices. Explain what it means to pair two Bluetooth devices and define
discoverable mode. Review the steps to make these pairings.
4. How To 3-2: Connect Your Phone to a Wi-Fi Network to Save Data Charges. Review the steps to
connect your phone to a Wi-Fi network.
5. Consider This: What are some uses of NFC devices? Survey students about their experience using
NFC technology.
TEACHER TIP
A memorable story about the origin of the name “Bluetooth” is likely to stick with students and
facilitate their remembering what Bluetooth technology is designed to achieve: Bluetooth was
developed by Ericsson in 1994 as a low-cost, powerful radio interface that could connect mobile
telephones to various devices. It was designed to work with different operating systems and was named
for a 10th-century Danish king, Harald Bluetooth, who united Denmark and Norway and reconciled
religious differences in the two countries.
1. Quick Quiz:
1) How does NFC technology transmit data between two NFC-enabled devices? (Answer: using
close-range radio signals)
2) In closed areas, the wireless range for Wi-Fi computers is about 300 feet. True or false? (Answer:
False)
3) What is a docking station? (Answer: an external device that attaches to a mobile computer or
device and contains a power connections and provides connections to peripheral devices)
2. Critical Thinking: As NFC technology emerges, what are some additional uses of this technology that
students could envision in addition to the ones in the text?
LAB ACTIVITIES
1. If possible, to help students better appreciate how these ports and connectors differ from one another,
bring them into the lab to see these ports on the back of some demonstration machines.

139: Protecting Hardware
LECTURE NOTES
• Discuss the kinds of threats (e.g., theft, vandalism) to which computers and mobile devices are
subject
• Discuss the use of device-tracking apps for determining the location of a lost or stolen computer
• Use Figure 3-27 to define the function of a fingerprint reader
• Discuss some of the reasons for hardware failure
• Define the following terms and discuss the implications thereof: undervoltage, brownout, blackout,
overvoltage (power surge), and spike
• Use Figure 3-28 to discuss the function of a surge protector (or surge suppressor)
• Use Figure 3-29 to discuss the function of an uninterruptible power supply (UPS)
FIGURES and TABLES: Figures — 3-27, 3-28, 3-29
BOXES
1. Internet Research: How prevalent is theft of mobile devices? Encourage students to experiment with
using the following search terms in their favorite search engine: mobile device theft.
2. BTW: Lost Computers or Devices. Encourage students to consider displaying their name and phone
number on the password screen as a way to potentially retrieve a lost computer, and remind students
3. How To 3-3: Evaluate Surge Protectors and UPSs. Explain what features to evaluate when purchasing
a surge protector or UPS. Review other factors to consider while evaluating.
4. Consider This: What other measures can organizations implement if their computers must remain
operational at all times? Explain what a fault-tolerant computer is and discuss the industries where this
technology is critical.
1. Quick Quiz:
1) What is a UPS? (Answer: a device that contains surge protection circuits and one or more
batteries that can provide power during a temporary or permanent loss of power)
2) An offline UPS always runs off the battery. True or false? (Answer: False)
142: Health Concerns of Using Technology
LECTURE NOTES
• Introduce some of the health concerns concomitant with the widespread use of technology
• Define repetitive strain injury (RSI), citing the examples of technology-related tendonitis and carpal
tunnel syndrome (CTS) using Figure 3-30
• Use Figure 3-31 to explain what computer vision syndrome (CVS) is
• Review some of the other ailments associated with extensive use of computers
• Define ergonomics and use Figure 3-32 to review the features of an ergonomic workspace
• Define technology addiction and technology overload

FIGURES and TABLES: Figures — 3-30, 3-31, 3-32
BOXES
1. Consider This: What can you do to prevent technology-related tendonitis or CTS? Survey students
about their own experience with pain or injuries related to their use of technology and review the
precautions listed.
2. How To 3-4: Evaluate Earbuds and Headphones. Explain what features to evaluate when purchasing a
earbuds or headphones. Review other factors to consider while evaluating based on your preferences
and needs.
3. Internet Research: What is a text neck? Encourage students to experiment with using the following
search terms in their favorite search engine: text neck.
4. Consider This: How can you tell if you are addicted to technology? Provide some of the symptoms of
users with technology addiction.
5. Now You Should Know: Be sure students understand the material in Ports and Connections,
Protecting Hardware, and Health Concerns of Using Technology sections, and how it relates to the
chapter objectives listed. Encourage students to discover more using the chapter’s premium content and
practice quizzes.
opportunities.
End of Chapter Material
▪ Study Guide materials reinforce chapter content.
▪ Key Terms present the terms from the text to help students prepare for tests and quizzes. Students
should know each Primary Term (shown in bold-black characters in the chapter) and be familiar
with each Secondary Term (shown in italic characters in the chapter).
▪ Checkpoint activities provide multiple-choice, true/false, matching, and consider this exercises to
reinforce understanding of the topics presented in the chapter.
▪ Problem Solving activities call on students to relate concepts to their own lives, both personally and
professionally, as well as provide collaboration opportunity.
▪ How To: Your Turn activities enable students to learn and to reinforce new practical skills with
personally meaningful and applicable exercises.
▪ Internet Research exercises require follow-up research on the web and suggest writing a short
article or presenting the findings of the research to the class.

▪ Critical Thinking activities provide opportunities for creative solutions to the thought-provoking
activities presented in each chapter. They are constructed for class discussion, presentation, and
independent research and designed for a team environment.
Glossary of Primary Terms
• all-in-one (114)
• Bluetooth (137)
• cloud computing (121)
• computer (108)
• computer vision
• syndrome (143)
• connector (135)
• desktop (114)
• digital camera (125)
• digital media player (128)
• e-book reader (129)
• embedded computer (132)
• ergonomics (144)
• game console (131)
• handheld game device (131)
• laptop (111)
• mobile computer (108)
• mobile device (108)
• NFC (138)
• overvoltage (140)
• port (134)
• portable media player (127)
• power surge (140)
• resolution (127)
• server (116)
• smartphone (123)
• surge protector (140)
• tablet (112)
• technology addiction (144)
• undervoltage (140)
• uninterruptible power
• supply (UPS) (140)
• USB port (136)
• wearable device (130)
• Wi-Fi (138)
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Glossary of Secondary Terms
• all-in-one desktop (114)
• activity tracker (130)
• application server (116)
• ATM (118)
• backup server (116)
• backward compatible (136)
• balance board (132)
• bar code reader (118)
• blackout (140)
• blade server (116)
• brownout (140)
• building automation systems (145)
• charge-coupled device (CCD) (126)
• common short code (CSC) (124)
• convertible tablet (112)
• CPU (110)
• CVS (143)
• dance pad (131)
• database server (116)
• discoverable mode (137)
• docking station (136)
• domain name server (116)
• DVD kiosk (120)
• earbuds (128)
• EarPods (128)
• e-book (129)
• enhanced resolution (127)
• e-reader (129)
• fault-tolerant computer (141)
• file server (116)
• fingerprint reader (139)
• FTP server (116)
• game server (116)
• gamepad (131)
• gaming desktop (114)
• Google Street View (111)
• handheld computer (112)
• home server (116)
• Internet of Things (133)
• jack (134)
• joystick (131)
• juice jacking (136)
• kiosk (119)
• list server (116)
• mail server (116)
• mainframe (117)
• media library (128)
• megapixel (MP) (127)
• MMS (multimedia message service) (124)
• motherboard (110)
• motion-sensing game controller (132)
• network server (116)
• noise cancelling (143)
• notebook computer (111)
• on-screen keyboard (123)
• optical resolution (127)
• pairing (137)
• peripheral device (108)
• personal computer (108)
• phablet (112)
• PIN (118)
• pixel (127)
• point-and-shoot camera (125)
• port replicator (136)
• portable keyboard (124)
• POS terminal (118)
• predictive text (123)
• print server (116)
• processor (111)
• pull notification (124)
• push notification (124)
• rack server (116)
• repetitive strain injury (RSI) (142)
• server farm (117)
• server virtualization (117)
• slate tablet (112)
• SLR camera (125)
• smart digital camera (125)
• smart eyewear (130)
• smartglasses (130)
• smartwatch (130)
• SMS (short message service) (124)
• spike (140)
• storage server (116)
• streaming media player (128)
• stylus (112)
• supercomputer (120)
• surge suppressor (140)
• swipe keyboard app (123)
• system unit (114)

• technology overload (144)
• telematics (133)
• terminal (117)
• text-to-speech feature (129)
• thin client (117)
• touch-sensitive pad (128)
• tower (114)
• tower server (116)
• ultrabook (111)
• USB hub (136)
• virtual keyboard (124)
• virtualization (117)
• visual voice mail (125)
• voice mail (125)
• wearable (130)
• web server (116)
• wheel (131)
• workstation (114)
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Exploring the Variety of Random
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drawing as in Fig. 207.
Fig. 208.—Sectional view of the generator and burner of the alcohol
vapor stove.
The alcohol flows from the supply tank through the pipe C to the
generator G, which is a brass tube filled with copper wires. The
vapor for starting the burner is generated by opening the valve V
and allowing a small amount of alcohol to flow through the orifice C
into the pan P directly below the generator. The valve is then closed
and the alcohol ignited. When the generating flame has burned out,
the valve V is again opened and the vapor which has generated in
the tube escapes at the orifice C and enters the Bunsen tube T, (Fig.
207) carrying with it the proper amount of air to produce the Bunsen
flame at each of the holes of the burner.
As in the case of the gasoline burners the orifice C sometimes
becomes clogged and it is necessary to insert a small wire to clear
the opening. With the stove is provided a tool for this purpose. With
stoves of this kind, the supply tank must not be tightly closed,
because any pressure in the tank would cause it to become
dangerous. The alcohol is fed to the generator entirely by gravity.
The stopper of the tank contains a small hole at the top which
should be kept open to avoid the generation of pressure should the
tank become accidentally heated.
Stoves of this kind may be conveniently used for a great variety of
household purposes, and when intelligently handled are relatively
free from danger.

Danger from Gaseous and Liquid Fuels.
—All combustible gases or vapors, when mixed within definite
amounts, are explosive. The violence of the explosion will be in
proportion to the volumes of the gas and the condition of
confinement.
When gasoline or other volatile fuel is vaporized in a closed room,
there is danger of an explosion, should the mixture of the vapor and
air reach explosive proportions. It is dangerous to enter a room with
a lighted match or open-flame lamp, where gaseous odor is
markedly noticeable. In case of danger of this kind the windows and
doors should be immediately opened to produce the most rapid
ventilation.
In the act of igniting the flame in a gas or vapor stove, the lighter
should be made ready before the gas is turned on. Explosions in gas
and vapor stoves are usually due to carelessness in igniting the fuel.
It should be kept constantly in mind that, if a combustible gas is
allowed to escape and mix with air in any space and then ignited, an
explosion of more or less violence is sure to occur.
Gasoline and kerosene are lighter than water and will float on its
surface. The flames from these oils are aggravated when water is
used in attempting to extinguish them. The burning oil floating on
the surface of the water increases the burning surface.
Burning oil must be either removed to a place where danger will not
result or the flames must be smothered. In case of a small blaze, the
fire may be extinguished with a cloth, preferably of wool, or if
circumstances will permit, with ashes sand or earth.
Alcohol dissolves in water and may, therefore, be diluted to a point
where it will no longer burn.
ACETYLENE-GAS MACHINES

Acetylene is a gas that is generated when water is absorbed by
calcium carbide, after the manner in which carbonic acid gas is
evolved when lime slakes with water, but with the liberation of a
larger amount of the combustible gas.
Calcium carbide is a product resulting from the union of lime and
coke, fused in an electric furnace to form a grayish-brown mass. It is
brittle and more or less crystalline in structure and looks much like
stone. It will not burn except when heated with oxygen. A cubic foot
of the crushed calcium carbide weighs 160 pounds.
Calcium carbide—or carbide as it is ordinarily termed—may be
preserved for any length of time if kept sealed from the air, but the
ordinary moisture of the atmosphere gradually slakes it and after
exposure for a considerable time it changes into slaked lime. The
carbide itself has no odor, but in the air it is always attended by the
penetrating odor of acetylene, because of the gas liberated by the
moisture absorbed from the air.
If protected from moisture, calcium carbide cannot take fire, being
like lime in this respect; it is therefore a safe substance to store. It is
transported under the same classification as hardware, and will keep
indefinitely if properly sealed.
A pound of pure carbide yields 5½ cubic feet of acetylene, but in
commercial form, as rated by the National Board of Fire
Underwriters, lump carbide is estimated at 4½ cubic feet per pound.
In the generation of acetylene, exact weights of carbide and water
always enter into combination, i.e., 64 parts of carbide to 34 parts of
water, and a definite amount of heat is evolved for each part of
carbide consumed.
Uncontrolled, the gas burns with a bright but not brilliant flame and
with a great deal of smoke, but when used in a burner suited for its
combustion it burns with a clear brilliant flame of a quality
approaching sunlight. While carbide is not explosive nor
inflammable, it may, if it finds access to water, create a pressure
such as to burst its container, and it is not impossible that heat

might be generated sufficient to ignite the gas under such
conditions. That such condition would often occur is not at all
probable. When water is sprinkled upon carbide, in quantity such
that it will all be taken up, the resultant slaked lime is left dry and
dusty, and occupies more space than the original carbide. When
more than enough water is employed, the remaining mixture of lime
and water is whitewash.
Chemically considered, acetylene is C H ; it is composed of carbon
and hydrogen and belongs to a class of compounds known as
hydrocarbons, represented in nature by petroleum, natural gas, etc.
It is composed of 92.3 per cent. carbon and 7.7 per cent. of
hydrogen, both combustible gases. It is a non-poisonous, colorless
gas, with a persistent and penetrating odor. Its presence in the air,
to the extent of 1 part in 1000 is distinctly perceptible. When
burning brightly in a jet, there is no perceptible odor. When
completely burned it requires for its combustion 2½ times its volume
of oxygen.
All combustible gases, when mixed with air and ignited, produce
more or less violent explosions. Acetylene is no exception to the
rule, and when allowed to escape into any enclosed space it will
quickly produce a violently explosive mixture, so that it is always
dangerous to enter a room or basement with a lamp or flame of any
kind where the odor of gas is perceptible. This is quite true with a
combustible gas of any kind, but with acetylene all mixtures from 3
to 30 per cent. are capable of being exploded with greater or less
violence.
The kindling point of acetylene is lower than coal gas or gasoline
gas. To ignite either of the latter gases, a flame is necessary to start
the combustion, but a spark or a glowing cigar is sufficient to ignite
acetylene. It should therefore be borne in mind that acetylene is not
only explosive when mixed with air but that it is very easy to ignite.
Under ordinary pressures pure acetylene is not explosive, but at
pressure above 15 pounds to the square inch explosions sometimes
occur where proper precautions are not observed. At all pressures
2 2

such as are required for household purposes acetylene is as safe for
use as any other gas.
Although acetylene is in danger of exploding when under pressure, it
is perfectly safe, when the proper conditions are observed, in tanks
for a great many kinds of portable lights.
Where acetylene is used in portable tanks under pressure,
advantage is taken of its solubility in acetone. This is a product of
the distillation of wood which possesses the property of absorbing
acetylene to a remarkable degree. In addition to this property is the
more important one of rendering the acetylene non-explosive when
under pressure. The tanks for its storage are filled with asbestos or
other absorbent material that is saturated with acetone. The
acetylene is then forced into the tanks under pressure and is
absorbed by the acetone. The safety of this means of storage lies in
the degree of perfection to which the tanks are filled with the
absorbent material. There must be no space anywhere in the tank
where undissolved acetylene can exist. Its freedom from danger
under such conditions has been thoroughly demonstrated in its use
for railroad and automobile lamps.
The use of acetylene as a fuel for cooking and for the various other
purposes of domestic use is successfully accomplished in burners
that give the blue flame desired for such purposes. Complete
cooking ranges and various other heating and cooking devices are
regularly sold by dealers in heating appliances, while water-heaters,
hot-plates, chafing-dish heaters, etc., are as much a possibility as
with any other of gaseous fuel and in as reasonably an inexpensive
way.
Coal gas, containing as it does sufficient carbon monoxide to render
it poisonous, will cause death when inhaled for any length of time,
but acetylene under the same conditions will have no deleterious
effect.
Types of Acetylene Generators.

Fig. 209.—Diagram of a carbide-
to-water acetylene-gas
generator.
Fig. 210.—Diagram of a water-
to-carbide acetylene-gas
machine.
—There are two general methods of generating acetylene for
domestic illuminating and heating purposes: that of adding carbide
to water, and that in which the water is mixed with carbide. The two
types are illustrated in the diagrams shown in Figs. 209 and 210.
The first method, that in which the carbide is dropped into water, is
shown in Fig. 209. The tank A is the generator and B is the receiver
or gas-holder. The tank A holds a considerable quantity of water and
is provided with a container C for holding the supply of carbide. The
tank A is connected with the gas-holders by a pipe which extends
above the water line in the tank B, where the gas is allowed to
collect in the gas-holder G. A charge of carbide, sufficient to fill the
holder with gas, is pushed into the tank A by raising the lever H.
Immediately the water begins to combine with the carbide and the
bubbles of gas pass up through the water and are conducted into
the tank B. The holder G is lifted by the gas and its weight furnishes
the pressure necessary to force the gas into the pipes, which
conduct it to the burners. If this machine were provided with the
proper mechanism to feed into the generator a supply of carbide
whenever the gas in the holder is exhausted, the machine would
represent the modern “carbide to water” generator.
T
h
e
“
water to carbide” generator is shown diagrammatically in Fig. 210.
As in the other figure, A is the generator and B is the gas-holder. A
supply of carbide S is placed in the generator and water from a tank

C is allowed to drip or spray onto the carbide. The gas collects in the
gas-holder as before. This apparatus represents in principle the parts
of a machine for generating acetylene by this process. The actual
machines are arranged to perform the functions necessary to make
the machines automatic in their action.
Whatever the type of the machine, the object is to keep in the
holders a sufficient amount of gas with which to supply the demand
made on the plant. Machines representing each of the types
described are to be obtained, but the greater number of those
manufactured are of the “carbide to water” form.
In the formative period of acetylene generators many accidents of
serious consequence resulted from imperfect mechanism.
Imperfections have been gradually eliminated until the machines
which have survived are efficient in action and mechanically free
from dangerous eccentricities.
The qualities demanded of a good generator are: There must be no
possibility of an explosive mixture in any of the parts; it must insure
a cool generation of gas; it must be well-constructed and simple to
operate; it should create no pressure above a few ounces; it should
be provided with an indicator to show how low the charge of carbide
has become in order that it may be recharged in due season, and it
must use up the carbide completely.
Because of the fact that the greater number of acetylene-gas
machines of today are of the “carbide to water” type, in the
description to follow that type of machine is used. They are
generally made in two parts, one part containing the generating
apparatus and the other acting as gasometer (gas-holder), but some
machines are made in which one cell contains both the generator
and gasometer.
In Fig. 211 is shown a two-part, gravity-fed machine, in which all of
the internal working parts are exposed to view. The tank (a), as in
the diagram, is the generator and the tank (b) contains the
gasometer marked G. Each tank possesses a number of appliances

which are necessary to make the machine automatic in its action.
The part C of the generator contains the supply of carbide, broken
into small pieces, a portion of which is dropped into the water
whenever additional gas is required. The feed mechanism F is
controlled by the gasometer bell G, which is buoyed up by the gas it
contains. When the supply of gas becomes low, the descending bell
carries with it the end of the lever F, which is attached to the feed
valve; this motion raises the feed valve and allows some of the
carbide to fall into the water. The gas that is immediately generated
passes into the gasometer through the pipe P, and as the bell is
raised by the accumulating gas the valve V is closed.
The gas as it enters the gasometer passes through a hollow device
W, that looks like an inverted T, the lower edge of which is tooth-
shaped and extends below the surface of the water. The gas, in
passing this irregular surface, is broken up and comes through the
water in little bubbles, in order that it may be washed clean of dust.
This device also prevents the return of the gas to the generator tank
during the process of charging.

Fig. 211.—Sectional view of the Colt acetylene-gas machine.
The gas escapes from the bell through the pipe S to the filter D,
where any dust that may have escaped the washing process is
removed by a felt filter. It finally leaves the machine by the pipe L, at
which point it enters the system through which it is conveyed to the
different lighting fixtures.
It will be noticed that the tank (b) is divided into two compartments,
the upper portion containing the water in which the gasometer

floats. The lower compartment is also partly filled with water which
acts as a safety valve to prevent any escape of gas into the room in
which the generator is located. The lower end of the pipes P and S
are immersed in the water at the bottom chamber of the tank, from
which the gas could escape in case too much is generated and
finally exit through the vent pipe U to the outside air.
The float A in the tank (a) is a safety device that prevents the
introduction of carbide unless the tank contains a full supply of
water. The float is a hollow metal cylinder connected by a rod to a
hinged cup under the bottom opening of the carbide holder. When
the water is withdrawn from the generator, the float falls and the
cup shuts off the carbide outlet.
Fig. 212.—Sectional view of a house equipped with acetylene lights and
domestic heating apparatus.
The accumulation of lime, from the disintegrated carbide, requires
occasional removal from the tank (a); the valve K is provided for this
purpose. The lever S is used to stir up the lime which is deposited on

the bottom of the tank, that it may be carried out with the
discharged water.
Machines of this kind that are safeguarded against leakage of gas or
the possibility of accumulated pressure are practically free from
danger in the use of acetylene. The accidental leakage of gas from
defective pipes and fixtures produce only the element of risk that is
assumed with the use of any other form of gas for illuminating
purposes.
Acetylene is distributed through the house in pipes in the same
manner as for ordinary illuminating gas. The sizes of the pipes to
suit the varying conditions of use are regulated by rules provided by
the National Board of Fire Underwriters. These rules state definitely
the sizes of pipes required for machines of different capacities. Rules
of this kind and others that specify all matters relating to the use of
acetylene may be obtained from any fire insurance agent.
The general plan of piping is shown in Fig. 212. The generator G is
in this case a “water to carbide” machine and is shown connected to
the kitchen range, as well as the pipe system which may be traced
to the lamps in the different rooms, to the porch lights and to the
boulevard lamp in front of the building.

Fig. 213.—
Acetylene gas
burner.
Fig. 214.—Electric
igniter for acetylene
gas burners.
Fig. 215.—Electric
igniter for acetylene
gas burners.
The type of burner used in acetylene lamps is shown in Fig. 213.
The gas issues from two openings to form the jet as it appears in
the engraving. These burners are made in sizes to consume ¼, ½,
¾, and 1 foot per hour depending on the amount of light
demanded.
Gas Lighters.
—The acetylene gas jets are lighted ordinarily with a match or taper
but electric igniters are often used for that purpose. Electric lighters
for acetylene lamps are practically the same as those used with
ordinary gas lamps but they must be adapted to the type of burner
on which they are used. Electric igniters that are intended to be
used with lamps placed in inaccessible places are different in
construction from those within reach. In Figs. 214 and 215 are
illustrated two forms of igniters that are intended to be used on
bracket or pendent lamps. They differ in mechanical construction to
suit two different conditions. Fig. 214 is an igniter in which is also
included the gas-cock. The gas is lighted by pulling a cord or chain
attached to the lever L. The movement of this lever turns on the gas
and at the same time brings the piece C in contact with the wire A to
complete an electric circuit. As the contact between these two pieces
is broken, a spark is formed that ignites the gas escaping from the
burner at B. On releasing the lever a spring returns the piece C to its
original position. The light is extinguished by a second pull of the
lever.
Fig. 215 illustrates a style of igniter which may be attached to an
ordinary gas-cock. It is attached to the stem of the burner by a
clamp D. The gas is turned on by the usual gas-cock and by pulling
the chain at the left the jet is lighted. In pulling the chain the arm A
is raised and carries with it the arm B. When the arms A and B
touch, an electric circuit is formed with a battery and spark coil.

Fig. 216.—Diagram of electric
igniters attached to gas burners.
When the desired position of the arms is reached, the points
separate to form an electric flash which lights the gas.
Fig. 216 illustrates in A the method
of installing electric igniters like
those described. A battery B and a
spark coil S are joined in circuit as
shown. The gas pipe acts as one of
the wires of the circuit. A battery of
four dry cells is commonly used for
the purpose. The spark coil is a
simple coil of wire wound on a
heavy iron core, which serves to
intensify the spark when the circuit
is broken. In using the igniter, it is
only necessary to see that the cells
are joined in series with the coil
and attached to the insulated part
of the igniter. As already explained
the action of the igniter is to close
the circuit and immediately break the contact at a point where the
spark will ignite the gas. On being released the igniter returns to its
original position.
In the fixture shown at C is an igniter such as is used in places that
cannot be conveniently reached. To light the jet, the circuit is
completed by turning the switch at W. As soon as the gas is lighted
the switch is again turned to break the igniter-circuit. In this device
the current passes through a magnet coil in the igniter which acts to
open and close the circuit with the same effect as in the others.
Acetylene Stoves.
—Stoves in which acetylene is used as a fuel are quite similar in
construction to those which burn coal gas. The principle of operation

is that of mixing the acetylene with air in proper proportion so as to
produce complete combustion when burned.

Discovering Computers Essentials 2016 1st Edition Vermaat Solutions Manual

CHAPTER XIII
ELECTRICITY
The adaptability of electricity to household use for lighting, heating
and the generation of power has brought into use a host of
mechanical devices that have found a permanent place in every
community where electricity may be obtained at a reasonable rate,
or where it can be generated to advantage in small plants.
Because of its cleanliness and convenience, electricity is used in
preference to other forms of lighting, even though its cost is
relatively high. Electric power for household purposes is constantly
finding new applications and will continue to increase in favor
because its use as compared with hand power is remarkably
inexpensive. Small motors adapted to most of the ordinary
household uses are made in convenient sizes and sold at prices that
are conducive to their greater use. Human energy is far too precious
to be expended in household drudgery where mechanical power can
be used in its place and often to greater advantage.
Electric heating devices compete favorably with many of the
established forms of household heating appliances, the electric flat-
iron being a notable example. In all applications where small
amounts of heat are required for short periods of time, electricity is
used at a cost that permits its use, in competition with other forms
of heating.
The remarkable advance that has taken place in electric transmission
in the past few years tends to an enormous increase in its use. The
constant increase in its use for lighting, heating and power purposes
is due in a great measure to the development of efficient electric
generating plants from which this energy may be obtained at the

least cost. In those communities where hydro-electric generation is
possible its field of application is almost without end.
Incandescent Electric Lamps.
—Anything made in the form of an illuminating device, in which the
lighting element is rendered incandescent by electricity, may
properly be called an incandescent lamp, whether the medium is
incandescent gas as in the Moore lamp, an incandescent vapor as
the Cooper Hewitt mercury-vapor lamp, or the incandescent filament
of carbon or metal such as is universally used for lighting.
From the year 1879, when Mr. Edison announced the perfection of
the incandescent electric lamp, until 1903, when for a short period
tantalum lamps were used, very little improvement had been made
in the carbon-filament lamp. Immediately following the introduction
of the tantalum lamp came the tungsten lamp, which because of its
wonderfully increased capability for producing light has extended
artificial illumination to a degree almost beyond comprehension. The
influence of the tungsten lamp has induced a new era of illumination
that has affected the entire civilized world. The development of the
high-efficiency incandescent lamp has brought about a revolution in
electric lighting. Its use is universal and its application is made in
every form of electric illumination.
Regardless of the immense number of tungsten lamps in use, the
carbon-filament lamp is still employed in great numbers and will
probably continue in use for a long time to come. In places where
lamps are required for occasional use and for short intervals of time,
the carbon filament still finds efficient use. In one form of
manufacture the carbon filament is subjected to a metalizing process
that materially increases its efficiency. This form, known
commercially as the GEM lamp, fills an important place in electric
lighting.
Of the rare-metal filament lamps, those using tungsten and tantalum
are in general use, but the tungsten lamps give results so much

superior in point of economy in current consumed that the future
filament lamps will beyond doubt be of that type unless some other
material is found that will give better results.
The filaments of the first tungsten lamps were very fragile and were
so easily broken that their use was limited, but in a very short time
methods were found for producing filaments capable of withstanding
general usage and having an average life of 1000 hours of service.
These lamps give an efficiency of 1.1 to 1.25 watts per candlepower
of light, as will be later more fully explained. This, as compared with
the carbon-filament lamps which average 3.1 to 4.5 watts per
candlepower, gives a remarkable advantage to the former. The
tungsten lamp has a useful life that for cost of light is practically
one-third that of the carbon-filament lamp.
The metal tungsten, from which the lamp filament is made, was
discovered in 1871. It is not found in the metallic state but occurs as
tungstate of iron and manganese and as calcium tungstate. Up to
1906 it was known only in laboratories and on account of its rarity
the price was very high. As greater bodies of ore were found and the
process of extraction became better known, the price soon dropped
to a point permitting its use for lamp filaments in a commercial
scale.
Pure tungsten is hard enough to scratch glass. Its fusing point is
higher than any other known metal; under ordinary conditions it is
almost impossible to melt it and this property gives its value as an
incandescent filament. One of the laws that affect the lighting
properties of incandescent lamps is: “the higher the temperature of
the glowing filament, the greater will be the amount of light
furnished for a given amount of current consumed.” The high
melting point permits the tungsten filament to be used at a higher
temperature than any other known material. Tungsten is not ductile,
and in ordinary form cannot be drawn into wire. Because of this fact,
the filaments of the first lamps were made by the “paste” process,
which consisted of mixing the powdered metal with a binding
material, in the form of gums, until the mass acquired a consistency

in which it might be squirted through a minute orifice in a diamond
dye. The resulting thread was dried, after which it was heated, and
finally placed in an atmosphere of gases which attacked the binding
material without affecting the metal. When heated by electricity in
this condition, the particles of metal fused together to form a
filament of tungsten. While the “paste” filaments were never
satisfactory in general use, their efficiency as a light-producing agent
inspired a greater diligence in the search for a more durable form.
Although tungsten in ordinary condition is not at all ductile, methods
were soon found for making tungsten wire and the wire-filament
lamps are now those of general use. One process of producing the
drawn wire is that of filling a molten mass of a ductile metal with
powdered tungsten after which wire is drawn from the mixture in the
usual way. The enclosing metal is then removed by chemical means
or volatilized by heat.
Of the difficulties encountered in the use of metal-filament lamps
that of the low resistance offered by the wire was overcome by using
filaments very small in cross-section and of as great length as could
be conveniently handled. The long tungsten filament requires a
method of support very different from the carbon lamp. The
characteristic form of tungsten lamps is shown in Fig. 217, in which
the various parts of the lamp are named.
The filament of an incandescent
lamp is heated because of the
current which passes through it.
The electric pressure furnished by
the voltage, forces current through
the filament in as great an amount
as the resistance will permit. A 16-
candlepower carbon lamp attached
to a 110-volt circuit requires
practically ½ ampere of current to
render the filament incandescent;
the filament resistance must,

Fig. 217.—An Edison Mazda lamp
and its parts.
therefore, allow the passage of ½
ampere. With a given size of
filament, its length must be such as
will produce the desired resistance. A greater length of this filament
would give more resistance and a correspondingly less amount of
current would give a dim light because of its lower temperature.
Likewise, a shorter filament would allow more current to pass and a
brighter light would result. When the size and length of filament is
once found that will permit the right amount of current to pass, if
the voltage is kept constant, the filaments will always burn with the
same brightness. This is in accordance with Ohm’s law which as
stated in a formula is
E = RC
that is E, the electromotive force in volts, is always equal to the
product of the resistance R, in ohms, and the current C, in amperes.
In the incandescent lamp, if the electromotive force is 110 volts and
the current is ½ ampere, the resistance will be 220 ohms and as
expressed by the law
110 = 220 × 0.5
From this it is seen that any change in the voltage will produce a
corresponding change in the current to keep an equality in the
equation. If the voltage increases, the current also increases and the
lamp burns brighter. Should the voltage decrease the current will
decrease and the lamp will burn dim. This dimming effect is
noticeable in any lighting system whenever there occurs a change in
voltage.
The quantity of electricity used up in such a lamp is expressed in
watts, which is the product of the volts and amperes of the circuit.
In the lamp described, the product of the voltage (110) by the
amount of passing current (½ ampere) is 55 watts. With the above
conditions the 16 candlepower of light will require 3.43 watts in the
production of each candlepower. The best performance of carbon-
filament lamps give a candlepower for each 3.1 watts of energy.

The filament of the tungsten lamp must offer a resistance sufficient
to prevent only enough current to pass as will raise its temperature
to a point giving the greatest permissible amount of light, and yet
not destroy the wire. The high fusing point and the low specific heat
of tungsten permits the filament to be heated to a higher
temperature than the carbon filament and with a less amount of
electric energy. These are the properties that give to the tungsten
lamp its value over the carbon lamp.
The exact advantage of the tungsten lamp has been investigated
with great care and its behavior under general working conditions is
definitely known. In light-giving properties where the carbon-
filament lamp requires 3.1 watts to produce a candlepower of light,
in the tungsten filament only 1.1 watts are necessary to cause the
same effect. The tungsten lamp therefore gives almost three times
as much light as the carbon lamp for the same energy expended.
The manufacturers aim to make lamps that give the greatest
efficiency for a definite number of hours of service. It has been
agreed that 1000 working hours shall be the life of the lamps and in
that period the filament should give its greatest amount of light for
the energy consumed.
The Mazda Lamp.
—The trade name for the lamp giving the greatest efficiency is
Mazda. The term is taken as a symbol of efficiency in electric
incandescent lighting. At present the Mazda is the tungsten-filament
lamp, but should there be found some other more efficient means of
lighting, which can take its place to greater advantage, that will
become the Mazda lamp.
Candlepower.
—The incandescent lamps are usually rated in light-giving properties
by their value in horizontal candlepower. This represents the mean
value of the light of the lamp which comes from a horizontal plane

passing through the center of illumination and perpendicular to the
long axis of the lamp. Candlepower in this connection originally
referred to the English standard candle which is made of spermaceti.
The standard candle is 0.9 inch in diameter at the base, 0.8 inch in
diameter at the top and 10 inches long. It burns 120 grains of
spermaceti and wick per hour. This candle is not satisfactory as a
standard because of the variable conditions that must surround its
use. The American or International standard is equal to 1.11 Hefner
candles. The Hefner candle (which is the standard in continental
Europe and South American countries) is produced by a lamp
burning amylacetate. This lamp consists of a reservoir and wick of
standard dimensions which gives a constant quantity of light. The
light from this lamp has proven much more satisfactory as a means
of measurement of light than the English standard and therefore its
use has been very generally adopted.
The light given out by an incandescent lamp is not the same in all
directions. In making comparisons it is necessary to define the
position from which the light of the lamps is taken. The horizontal
candlepower affords a fairly exact means of comparing lamps which
have the same shape of filament, but for different kinds of lamps it
does not give a true comparison. The spherical candlepower is used
to compare lamps of different construction as this gives the mean
value at all points of a sphere surrounding the lamp. The
candlepower is measured at various positions about the lamp with
the use of a photometer, and the mean of these values is taken as
the mean spherical candlepower.
At their best, carbon-filament lamps require in electricity 3.1 w.p.c.
(watts per candlepower). As the lamp grows old the number of watts
per candle power increases, until in very old lamps the amount of
electricity used to produce a given amount of light may become
excessively large. According to a bulletin issued by the Illinois
Engineering Experiment Station on the efficiency of carbon-filament
incandescent lamps, the amount of electrical energy per
candlepower varied from 3.1 w.p.c., when new, to 4.2 w.p.c., after
burning 800 hours.

A common practice in the use of carbon-filament lamps is to
consider that the period of useful life ends at a point where the
amount of electricity, per candlepower, reaches 20 per cent. in
excess of the original amount. This point (sometimes termed the
smashing point) would be reached after 800 working hours,
according to the Illinois Station, and at about 1000 hours as stated
by the bulletins of the General Electric Co. If a carbon-filament lamp
burns for an average period of 3 hours a day for a year, it ought to
be replaced.
The Edison screw base as shown in Fig. 217 is now generally used in
all makes of incandescent lamps for attaching the lamp to the
socket. When screwed into place this base forms in the socket the
connections with the supply wires, to produce a circuit through the
lamp. One end of the filament is attached to the brass cap contact;
the opposite end connects with the brass screw shell of the base.
When the current is turned on, the contact made in the switch is
such as to form a complete circuit between the supply wires; the
voltage sending a constant current through the lamp produces a
steady incandescence of the filament.
In Fig. 218 is shown a carbon-filament lamp attached to an ordinary
socket. The lamp base and socket are shown in section to expose all
of the parts that comprise the mechanism. The insulated wires of
the lamp cord enter the top of the socket and the ends attach to the
binding screws A and B, which are insulated from each other and
form the brass shell which encases the socket. The lamp base is
shown screwed into the socket, the brass cap contact F making
connection at G; the screw shell joins the socket at D. To the key S
is attached a brass rod R, on which is fastened E, the contact-maker.
The rod R passes through a supportary frame which is secured to
the lamp socket at G. As shown in the figures the piece E makes
contact with a brass spring attached to A, and this completes a
circuit through the filament. The brass cap contact of the lamp base
makes connection at one end of the filament H, the other end of the
filament K is attached to the brass screw shell of the base, which in
turn connects with the screw shell of the socket and this shell is

Fig. 218.—Section of a lamp
base and socket.
connected with the piece containing the binding screw B by the rod
C to complete the circuit. When the key S turns, the contact above E
is broken and the lamp ceases to burn.
Fig. 118 shows the use of an
adapter that is sometimes
encountered in old electric fixtures,
the use of which requires
explanation. Mention has already
been made of the various forms of
lamp sockets in use before the
Edison base became a standard. In
order to use an Edison lamp in a
socket intended for another form of
base an adapter must be employed
to suit the new base to the old
socket. In the figure the piece P ,
is the adapter. This is intended to
adapt the standard lamp base to a
socket that was formerly in use on
the Thompson-Houston system of
electric lighting. The adapter is
joined to the old socket by the
screw at G and the circuit formed
as already described.
Lamp Labels.
1

—For many years all incandescent lamps were rated in candlepower
and were made in sizes 8, 16, 32, etc., candlepower. On the label
was printed the voltage at which the lamp was intended to operate,
and also the candlepower it was supposed to develop. Thus 110 v.,
16 cp. indicated that when used on 110-volt circuit, the lamp would
give 16 candlepower of light. This label in no way indicated the
amount of energy expended. With the development of the more
efficient filaments came a tendency to label lamps in the amount of
energy consumed. This has resulted in all lamps being labeled to
show the voltage of the circuit suited to the lamp, and the watts of
electricity consumed when working at that voltage. At present a
lamp label may be marked 110 v., 40 w., which indicates that it is
intended to develop its best performance at 110 volts and will
consume 40 watts at that voltage.
Commercial lamps are now manufactured in sizes of 10, 15, 25, 40,
60, 75, and 100 watts capacity for ordinary use. Of these the 40-
watt lamp probably fulfills the greatest number of conditions and is
most commonly used. Besides these there are the high-efficiency
lamps of the gas-filled variety that are made in larger sizes and the
miniature lamps in great variety. All are labeled to show the volts
and the watts consumed.
Illumination.
—The development of high-efficiency lamps has caused a radical
change in the methods of illumination. With cheaper light came the
desire to more nearly approximate the effect of daylight in
illumination. This has brought into use indirect illumination, in which
the light from the lamp is diffused by reflection from the ceiling and
walls of the room. Illuminating engineering is now a business that
has to do with placing of lamps to the greatest advantage in lighting
any desired space. In large and complicated schemes of lighting
professional services are necessary, but in household lighting the
required number of lamps for the various apartments are almost
self-evident. The lighting of large rooms, however, requires

thoughtful consideration and in many cases the only definite solution
of the problem is that of calculation.
The Foot-candle.
—The amount of illumination produced over a given area depends
not only on the number of lamps and their candlepower, but upon
their distribution and the color of the walls and furnishings. In the
calculation of problems in illumination, units of measure are
necessary to express the amount of light that will be furnished at
any point from its source. The units adopted for such purposes are
the foot-candle and the lumen.
The Lumen.
—A light giving 1 candlepower, placed in the center of a sphere of 1
foot radius illuminates a sphere, the area of which is 4 × 3.1416 or
12.57 square feet. The intensity of light on each square foot is
denoted as a candle-foot. The candle-foot is the standard of
illumination on any surface. The quantity of light used in illuminating
each square foot of the sphere is called a lumen. A light of 1
candlepower will therefore produce an intensity of 1 candle-foot over
12.57 square feet and give 12.57 lumens. Therefore, if all of the
light is effective on a plane to be illuminated, a lamp rated at 400
lumens would light an area of 400 square feet to an average
intensity of 1 candle-foot.
To find the number of lamps required for lighting any space, the
area in square feet is multiplied by the required intensity in foot-
candles, to obtain the total necessary lumens, and the amount thus
obtained is divided by the effective lumens per lamp.
The bulletins of the Columbia Incandescent Lamp Works gives the
following method of calculating the number of lamps required to
light a given space:

Number of lamps = (S × I)/(Effective lumens per lamp)
S (square feet) × I (required illumination in foot-candles)
= total lumens.
The total lumens divided by the number of effective lumens per
lamp gives the number of lamps required. In using the formula the
effective lumens per lamp is taken from the following table:
Watts per lamp 25 40 60 160 150 250
Effective lumens per lamp 95 160 250 420 630 1090
Lumens per watt 3.8 4.0 4.2 4.2 4.2 4.3
The size of the units is a matter of choice since six 400-lumen units
are equal to four 600-lumen units in illuminating power, etc. In
deciding upon the proper size of lamps to use, consideration must be
taken of the outlets if the building is already wired. In general the
fewest units consistent with good distribution will be the most
economical. The table shows the lumens effective for ordinary
lighting with Mazda lamps and clear high-efficiency reflectors with
dark walls and ceiling. Where both ceiling and walls are very light
these figures may be increased by 25 per cent.
To illustrate the use of the table, take an average room 16 by 24 to
be lighted with Mazda lamps to an intensity of 3.5 foot-candles. If
clear Holoplane reflectors are used, the values for lumens effective
on the plane may be increased 10 per cent. due to reflection from
fairly light walls. The lamps in this case are to be of the 40-watt type
which in the table are rated at 160 lumens. To this amount 10 per
cent. is added on account of the reflectors and walls. This data
applied to the formula gives:
s = 16 by 24 feet
I = 3.5
Lumens per lamp = 160
((16 × 24) × 3.5)/176 = eight 40-watt lamps.

Fig. 219.
Reflectors.
—The character and form of reflectors have much to do with the
effective distribution of the light produced by the lamp. The most
efficient form of reflectors are made of glass and designed to project
the light in the desired direction. The illustration in Fig. 219, marked
open reflector, shows the characteristic features of reflectors
designed for special purposes. They are made of prismatic glass
fashioned into such form as will produce the desired effect and at
the same time transmit and diffuse a part of the light to all parts of
the space to be lighted. The greater portion of the light is sent in the
direction in which the highest illumination is desired. The reflectors
are made to concentrate the light on a small space or to spread it
over a large area as is desired. They are, therefore, designated as
intensive or extensive reflectors and made in a variety of forms.

Choice of Reflector.
—Where the light from a single lamp must spread over a relatively
great area, it is advisable to use an extensive form of reflector. This
reflector is applicable to general residence lighting, also uniform
lighting of large areas where low ceilings or widely spaced outlets
demand a wide distribution of light. Where the area to be lighted by
one lamp is smaller, the intensive reflector is used. Such cases
include brilliant local illumination, as for reading tables, single-unit
lighting or rooms with high ceilings as pantries or halls.
Where an intense light on a small area directly below the lamp is
desired, a focusing reflector is used. The diameter of the circle thus
intensely lighted is about one-half the height of the lamp above the
plane considered. Focusing reflectors are used in vestibules or rooms
of unusually high ceilings.
Type Height above plane to be lighted
Extensive ⁄ D
Intensive ⁄ D
Focusing ⁄ D
D = distance between sides of room to be illuminated.
The various other fixtures of Fig. 219 that are designated as
reflectors are in some cases only a means of diffusion of light. In the
use of the high-efficiency gas-filled lamps the light is too bright to be
used directly for ordinary illumination. When these lamps are placed
in opal screens of the indirect or the semi-indirect form the light
produced for general illumination is very satisfactory. Considerable
light is lost in passing through the translucent glass but this is
compensated by the use of the high-efficiency lamps and the
general satisfaction of light distribution.
Lamp Transformers.
—Lamps of the Mazda type, constructed to work at the usual
commercial voltages, are made in low-power forms to consume as
1
2
4
5
4
3

little as 10 watts; but owing to the difficulty of arranging a suitable
filament for the smaller sizes of lamps, less voltage is required to
insure successful operation. The lamps for this purpose are of the
type used in connection with batteries and require 1 or more volts to
produce the desired illumination. When these little lamps are used
on a commercial circuit, the reduction of the voltage is accomplished
by small transformers, located in the lamp socket. The operating
principle and further use of the transformers will be explained later
under doorbell transformers. The lamp transformer, although
miniature in design, is constructed as any other of its kind but
designed to reduce the usual voltage of the circuit to 6 volts of
pressure. The socket is that intended for the use of the Mazda
automobile lamp giving 2 candlepower. This lamp used with
electricity at the average rate per kilowatt can be burned for 10
hours at less than half a cent. In bedrooms, sickrooms and other
places where a small amount of light is necessary but where a
considerable quantity is objectionable, the miniature lamp
transformer serves an admirable purpose in adapting the voltage of
the commercial alternating circuit to that required for lamps of small
illuminating power. Such a transformer is shown in Fig. 220.
Fig. 220.—Miniature lamp transformer complete and the parts of which
it is composed.
The figure shows in A the assembled attachment with the lamp bulb
in place. The part B, the transformer, changes the line voltage to
that of a battery lamp. A line voltage of 110 may be transformed to
suit a 6-volt miniature lamp. The parts C and D compose the screw
base and the cover, in which is fitted the transformer B.

Units of Electrical Measurement.
—The general application of electricity has brought into common use
the terms necessary in its measurement and units of quantity by
which it is sold. The volt, ampere and ohm are terms that are used
to express the conditions of the electric circuit; the watt and the
kilowatt are units that are employed in measuring its quantity in
commercial usage. The use of these units in actual problems is the
most satisfactory method of appreciating their application.
As already explained the volt is the unit of electric pressure which
causes current to be sent through any circuit. The electric circuits of
houses are intended to be under constant voltage—commonly 110
or 220—but the voltage may be any amount for which the
generating system is designed. Independent lighting systems such
as are used in house-lighting plants—to be described later—
commonly employ 32 volts of electric pressure.
Opposed to the effect of the volts of electromotive force is the
resistance of the circuit, which is measured in ohms. Resistance has
been called electric friction; it expresses itself as heat and tends to
diminish the flow of current. Every circuit offers resistance
depending on the length, the kind and the size of wire used. Since
the wires of commercial lighting systems are made of copper, it can
be said that the resistance of the circuit increases as the size of the
conducting wire decreases. In large wires the resistance is small but
as the size of the wire is reduced the resistance is increased. A long
attachment cord of a flat-iron, may offer sufficient resistance to
prevent the iron from heating properly.
The ampere is the unit which measures the amount of current. The
amperes of current determine the rate at which the electricity is
being used in any circuit. The wires of a house must be of a size
sufficient to carry the necessary current without heating. Any house
wire which becomes noticeably warm is too small for the current it
carries and should be replaced by one that is larger.

The watt is the unit of electric quantity. The quantity of electricity
being used in any circuit is the product of the volts of pressure and
amperes of current flowing through the wires. The amount of
current—in amperes—sent through the circuit is the direct result of
the volts of pressure; the quantity of electricity is therefore the
product of these two factors. A 25-watt lamp on a circuit of 110 volts
uses 0.227 ampere of current.
25 watts = 110 volts × 0.227 amperes.
Ten such lamps use
10 × 0.227 amperes = 2.27 amperes.
The product of 110 volts and 2.27 amperes is 250 watts.
In order to express quantity of energy, it is necessary to state the
length of time the energy is to act and originally the watt
represented the energy of a volt-ampere for one second. For
commercial purposes this quantity is too small for convenient use
and the hour of time was taken instead. The watt of commercial
measurement is the watt-hour and in the purchase of electricity the
watt is always understood as that quantity.
Even as a watt-hour the measure is so small as to require a large
number to express ordinary amounts and a still larger unit of 1000
watt-hours or the kilowatt-hour was adopted and has become the
accepted unit of commercial electric measurement. Just as a dollar
in money conveniently represents 1000 mills so does a kilowatt of
electricity represent a convenient quantity.
In the purchase of electricity, the consumer pays a definite amount,
say 10 cents per kilowatt. This represents an exact quantity of
energy, that may be expended in light, in heat, or in the generation
of power, all of which may be expressed as definite quantities.
As light, it indicates in the electric lamp the number of candle-
power-hours that may be obtained for 10 cents. At this rate a single
watt costs 0.01 cent an hour. A 25-watt electric lamp will therefore
cost 0.25 (¼) cent for each hour of use; a 60-watt lamp costs 0.6

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