Resistance

Resistance

It is the property of a substance which opposes or resists the flow of current.

R= ϱ L/A

where, 'ϱ' is the resistivity of the substance.

If L=1 unit, A = 1 Square unit

Then, R = ϱ 

It means that ϱ is also the resistance when L=1 unit and A = 1 Square unit.

Factors affecting the resistance of a substance

The resistance of a substance depends upon the following 4 factors.

1. The resistance of a conductor varies directly as its length i.e. as length of conductor increases resistance also increases and vice-versa. Mathematically,

R α L

2. The resistance of the conductor varies inversely as its cross section area i.e. as cross section increases resistance decreases and vice-versa.

R α (1/A)

3. The resistance of a conductor depends on the nature of the material. For Eg. : Ag, Cu, Al has low value of resistivity and wood, mica, glass has high value of resistivity.

4. The depends on its temperature also if temperature increases the resistance of conductor also increases.

Hence, resistance of conductor depends on length, cross sectional area, nature of material and temperature.