1. RESISTANCE

2. DEFINED - Opposition to electron flow.
- The resistance in a metal conductor is directly proportional to the length and inversely proportional to the cross-sectional area.
R=Resistance
р=specific resistance
l=length
A=Cross-Sectional Area

3. DEFINED - Increase in temperature will also increase resistance.
-Resistance is measured in Ohms (Ω)
-Resistance sounds like a bad thing but we tend to use it to our advantage in most circuits.

4. THEORY Notice Thus anytime as the resistance current needs to
be limited in a circuit,
a resistor can be added.
Notice
as the resistance
increases the current
decreases.
Resistance
Current

5. RESISTORS
Resistors are devices that turn electrical current into heat energy. This is valuable to limit current flow to another portion of a circuit.
There are two main types of resistors, fixed and variable. The variable resistor may also be called a potentiometer.
How can we determine the resister’s value? There are two ways - measuring with a meter or reading the color code.
The schematic symbols for each type are on the right. The arrow is used to denote a resistor that is variable or controllable.
Schematics
Fixed Resistors
Potentiometers

6. Resistance Color Code First Number Second Number Tolerance /Accuracy
Fixed resistors use color bands to make it easy to read their resistance from any angle or position
Number of Zeros or if:
Gold - divide by 10
Silver - divide by 100

7. Black = 0 Brown = 1 Red = 2 Orange =3 Yellow = 4 Green = 5 Blue = 6
Violet = 7
Gray = 8
White = 9
Third color band:
gold = divide by 10
silver = divide by 100
Fourth color band:
gold = 5 % = .05
silver = 10 % = .10
Number of Zeros
First Number
Second Number
Accuracy 4 7
0 0
Ohms
@ 10 % accuracy

8. Black = 0 Brown = 1 Red = 2 Orange =3 Yellow = 4 Green = 5 Blue = 6
Violet = 7
Gray = 8
White = 9
Third color band:
gold = divide by 10
silver = divide by 100
Fourth color band:
gold = 5 % = .05
silver = 10 % = .10
Use the accuracy band to determine the resistors acceptable range of resistance 5 6
0 0 0
@ 10 %
Acceptable Range
.10
Highest
Lowest