![Why copper conducts electricity while glass
does not?
Because of the free
electrons. The atom
easily loses the
outer electron
The Copper atom has 29
electrons [2 + 8 + 18 +1].](https://image.slidesharecdn.com/chapter1-basicconcepts-240329000759-c613bc6d/85/Electric-Circuit-1-Chapter-1-Basic-Concepts-of-Circuits-11-320.jpg)
Electric Circuit 1 Chapter 1 Basic Concepts of Circuits
- 2. Contents • Electric Circuit • Voltage • Current • Conductors • Insulators • Energy • Power
- 3. Electric Circuit • Electric Circuit – A mathematical model that approximates the behavior of an actual electrical system.
- 4. A simple electric circuit
- 5. Would This Work? No. The loop is not closed.
- 6. Would This Work? Yes. Only this connection works, closed loop.
- 7. Circuits
- 8. The Atom
- 9. 1.2 Electric Charges • Charge is an electrical property of the atomic particles of which matter consists, measured in coulombs (C). • The charge e on one electron is negative and equal in magnitude to 1.602 10-19 C which is called as electronic charge. • 1 C = 6.242 x 1018 electrons
- 10. Electric Charge (Cont’d) • Important characteristics of electric charge (q): – Bipolar (+, -) • Electron (-), Proton (+) – Discrete quantities, 1.6022x10-19 C • Electron (-1.6022x10-19 C), Proton (+1.6022x10-19 C), Neutron (0 C)
- 11. Why copper conducts electricity while glass does not? Because of the free electrons. The atom easily loses the outer electron The Copper atom has 29 electrons [2 + 8 + 18 +1].
- 12. What is an electric current? An electric current is a flow of electrons through wires and components. + - In which direction does the current flow? from the Positive terminal to the Negative terminal of a cell. The electrons flow from the negative terminal to the Positive terminal.
- 13. • Electricity flows when electrons travel through a conductor. • Only some materials have free electrons inside. Conductors: YES! Insulators: NO! No free electrons = No current • We call this flow “current.” silver copper gold aluminium iron steel brass bronze mercury graphite glass rubber asphalt fiberglass porcelain ceramic quartz (dry) cotton (dry) paper (dry) wood plastic air diamond Conductors and Insulators
- 14. Platinum
- 15. Copper Silver
- 16. Aluminum Gold
- 17. Example Example A conductor has a constant current of 5 A. How many electrons pass a fixed point on the conductor in one minute?
- 18. Solution Solution Total no. of charges pass in 1 min is given by 5 A = (5 C/s)(60 s/min) = 300 C/min Total no. of electrons = 300 x 6.242 x 1018 = 1.87x1021 electrons/min Total no. of electrons pass in 1 min is given min electrons/ 10 87 . 1 C/electron 10 602 . 1 C/min 300 21 19 x x
- 19. Voltage • The separation of charge creates an electric force – Voltage • analogous to ‘pressure’ between two points • Whenever positive and negative charges are separated, energy is expended • Voltage is the energy per unit charge created by the separation dq dw v where v = the voltage in volts w = the energy in joules q = the charge in coulombs
- 20. What Produces Voltage? V = “Electrical pressure” A Battery Electric Power Plant Lab Power Supply Nerve Cell 1.5 V 9 V 400,000 V A few Volts Solar Cell A few millivolts when activated by a synapse
- 21. Power and Energy • Power is the time rate of expending or absorbing energy dt dw p where p = the power in watts w = the energy in joules t = the time in seconds • Power is associated with the flow of charge vi dt dq dq dw dt dw p where p = the power in watts v = the voltage in volts i = the current in amperes
- 22. Power Polarity 1 2 + - v i 1 2 + - v i 1 2 - + v i 1 2 - + v i p = vi p = -vi p = -vi p = vi
- 23. Algebraic Sign of Power • + (p>0) – Power is being delivered to the circuit inside the box • - (p<0) – Power is being extracted from the circuit inside the box
- 24. 1.5 Power and Energy (2) • The law of conservation of energy 0 p • Energy is the capacity to do work, measured in joules (J). • Mathematical expression t t t t vidt pdt w 0 0
- 25. Reference polarities for power using passive sign convention Power delivered Power absorbed
- 26. Symbols for independent voltage source 26
- 27. Symbols for independent current source 27
- 28. Symbols for a) dependent voltage sources b) dependent current sources
- 29. What is the total voltage, if each battery is 1.5 v?
- 30. Circuit Elements (1) Example Obtain the voltage v in the branch shown for i2 = 1A.
- 31. Solution Voltage v is the sum of the current-independent 10-V source and the current-dependent voltage source vx. Note that the factor 15 multiplying the control current carries the units Ω. Therefore, v = 10 + vx = 10 + 15(1) = 25 V
- 32. Voltage, Current, and Power • One Volt is a Joule per Coulomb (J/C) • One Amp of current is one Coulomb per second (6.24 x1018 electrons/second). • For one volt (J/C) and one amp (C/s), then multiplying gives Joules per second (J/s) – this is power: J/s = Watts • So the formula for electrical power is just: P = VI: power = voltage current
- 33. A wrong question in your textbook This example has an error, solve the circuit to identify it. Example 1.7 Page 16 (this example has an error) Calculate the power delivered or absorbed by each element in the circuit
- 34. • Chapter 1- Problem 18 Determine the power of each element (absorbed /delivered).
- 35. Problem 19 Modified. Determine the power of each element (absorbed /delivered). Then find the current I using the Power Conservation .
- 36. Class Discussions Problem 21 Modified • A 60-W, incandescent bulb operates at 240 V. How many coulombs flow through the bulb in one day?
- 37. Thank you