1. Chapter 5: Resistors

2. What is a resistor?
Definition: 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
Resistors work as they turn voltage energy into heat
2 Functions:
To limit current
To produce desired voltage
Analogy

3. Resistors

4. Resistor’s Schematic Symbol
Composed of a zig-zag line
What is the value of the resistor on the right?
Reference Designators
300 Ω
30kΩ

5. Surface Mount vs. Through Hole

6. Types of Fixed Resistors
Carbon Compostion
Metal Film
Metal-Oxide Film
Resistor Networks
Wirewound Resistors
Old-skool
High accuracy
Low noise and good thermal properties
High accuracy at high resistance
Many packaged resistors
High power applications

7. Surface Mount Resistors (SMT)
Surface Mount Technology

8. Resistor Properties Value in Ohms Accuracy
Power rating (We’ll look at this one first)

9. What is Resistor Power Rating?
Examples:
¼ watt, ½ Watt, 20 watts
P = V*I = V2/R
Heat Sinks

10. Determining Value and Accuracy
Tolerance Color Code:
Brown = 1%
Red = 2%
Gold = 5%
Silver = 10%

11. Video See lecture notes first

12. More in class practice problems
Blue Blue Blue Gold
66 MΩ +/- 3.3 MΩ
Brown Black Red Silver
1000 Ω +/- 100 Ω
Brown Black Orange Silver
10000 Ω +/ Ω
Orange Violet Black Gold
37 Ω +/ Ω
Find tolerance range as well
… or you can just measure it with an Ohmmeter!

13. Reading Resistor Value on a Surface Mount Resistor
324
320,000 Ω
670
67 Ω
103
10k Ω
100
10 Ω

14. Homework Do problems 1 and 2 on page 85
Include the range (if applicable)!

15. Variable Resistors

16. Pictures of Variable Resistors

17. Linear vs. Logarithmic “Pots”

18. Knob rotation (Usually 20 turns)
Linear vs. Logarithmic “Pots”
Knob rotation (Usually 20 turns)
See page 69 for schematic of application

19. Resistance of a Wire The longer a wire is, the more resistive it is.
The thicker a wire is, the less resistive it is. (Think parallel)
(Also think of a fire hose. There is always pressure drops across a pipe, but less pressure drop for bigger hoses.)
Resistance is given by the following equation
Therefore as a wire gets longer, the resistance change gets linearly larger.
“The larger the cross-sectional area of the conductor, the more electrons are available to carry the current, so the lower the resistance. The longer the conductor, the more scattering events occur in each electron's path through the material, so the higher the resistance. Different materials also affect the resistance.”

20. Random Video of the Day