Resistance

Electrical resistance is a measure of the degree to which an object opposes the passage of an electric current. The SI unit of electrical resistance is the ohm. Its reciprocal quantity is electrical conductance measured in siemens. Resistance is the property of any object or substance of resisting or opposing the flow of an electrical current. The quantity of resistance in an electric circuit determines the amount of current flowing in the circuit for any given voltage applied to the circuit.

Where R is the resistance of the object, usually measured in ohms. V is the potential difference across the object, usually measured in volts I is the current passing through the object, usually measured in amperes

Color Coding in Resistors : Resistor Color Code Resistance value, first three bands. 1st band – 1st digit 2nd band – 2nd digit 3rd band – number of zeros.

0

Black

1

Brown

2

Red

3 Orange 4

Yellow

5

Green

6

Blue

7

Violet

8

Gray

9

White

A variation on the color code is used for precision resistors which may have five colored bands. In that case the first three bands indicate the first three digits of the resistance value and the fourth band indicates the number of zeros. In the five band code the fifth band is gold for 1% resistors and silver for 2%.