Question

A wire is stretched to half of original radius the
resistance of stretched wire becomes.
(1) 4 times
(2) 8 times
(3) 16 times
(4) 32 times​

Answer 1

Answer:

1) 4 times

Explanation: Because when cross section decreases length increases i.e the wire is stretched and area of cross section is decreased to half

Answer 2

When a wire is stretched to half of the original radius, then the resistance of stretched wire becomes (1) 4 times.

Resistance= Resistivity × length/area

On stretching the wire to double length, the cross section area is reduced to half.

Therefore,

New Resistance = Resistivity × 2 × length/area/2

Resistivity × length/area)x4

= Resistance × 4

Thus, on stretching the wire, resistance is multiplied by four times.