Introduction to Electronics - Resistors
- 1. Introduction to Electronics: Section One: Resistors James Noll - Instructor
- 2. Resistors Resistors are defined as: “A device used in electrical circuits to maintain a constant relation between current flow and voltage.” Resistors are used to step up or lower the voltage at different points in a circuit and to transform a current signal into a voltage signal or vice versa, among other uses. The electrical behavior of a resistor obeys Ohm's law for a constant resistance
- 3. Resistors The unit of measurement of a resistor is the “ohm” Resistors are made of several types of materials including carbon, metal film and wire. Each material gives each type of resistor a certain “characteristic”. For instance, carbon is a common resistor material used for general purpose resistors. Metal Film is a material that is used for precision resistors and is more delicate than carbon. Wire is used for high power, high current applications and is considered heavy duty.
- 4. Resistors Resistors are generally a “two-lead” device Each resistor type has a “tolerance” or percentage accuracy – 1%, 5%, 10%, 20%, etc. Some resistors are color coded while others have printed information on them. The color code will be explained later. Resistors are considered a passive device and are a fixed value. Potentiometers are a variable resistor.
- 5. Resistors
- 6. Resistors Resistors have a wide range of values: − Resistors range in value from less than 1 ohm to over one million ohms. − Each resistor has a “suffix” to indicate it's value − For resistors less than one thousand, there is no suffix. − For resistors greater than one thousand, the suffix is “K” − For resistors greater than one million, the suffix is “M”
- 7. Resistance Formulas The basic formula for resistance is: − R=E/I where R is resistance, E is voltage and I is current. − The formula is used in Direct Current circuits only.