Resistance (R)

Resistance (R)

Resistance is property of a conductor to resist the flow of charges through it.

According to Ohm's Law, R = V / I

From this equation, we could say that Resistance (R) is inversely proportional to current (I) flowing through a resistor.

R α 1 / I ----- 1

I  α 1 / R ----- 2

Here is a new formula for the Resistance (R):

Current (I) flowing through a wire decreases by one-half when the length of the wire (L) is doubled.

I α 1 / length of wire(L) ------ 3

Current (I) flowing through a wire is increased as thickness of the wire is increased for the same material and same length.

I α area of cross-section (A) ------ 4

Current (I) flowing through the wire is also dependent on the material of the wire.

From 3 and  4,

I α A / L ----- 5

From 5 and 2

I α 1/ R α A / L

Therefore,

1 / R α A / L

On cross multiplying,

R α L / A

Therefore,  Resistance α Length of the wire / Area of cross section

To remove proportionality sign, we introduce a constant ρ (rho)

R =  ( ρ L) / A ; ρ(rho) is a constant which differ based on the nature of material of the wire.

R =  ( ρ L) / A ----- 6