Question

A wire of given material having length L and are of cross-section A has a resistance of 4 ohm,s. What would be the resistance of another wire of the same material having length l/2 and area of cross-section 2A?

Answer 1

Answer:

Resistance = p l/a [ p is constant]

For first wire length = l and area of croos section = a

Resistance = p l/a = 4 ohm [given]

For second wire length = l/2 and area of cross section = 2a

Resistance = p (l/2) / 2a

                   = p l/4a

                   = p l/a * 1/4 [p l/a = 4 ohm]

                   = 4*1/4 =  1 ohm

The resistance of second wire = 1 ohm