Question

if a wire of resistance R is melted and recast t half of its length , then new resistance of wire will be

Answer 1

Answer:

New resistance R' = 1/4th of the initial resistance

Explanation:

let the initial length be 'L' and area of cross section be 'A'

then the resistance = rho*( L/A) = rho*(L÷A) = R

after melting and recasting....

new length = L/2

new area = 2A ( because the volume of wire never changes and to keep volume same area is twice the new length )

so the new resistance =

rho*(L/2 ÷ 2A)

rho*( L/4A)

1/4[ rho*( L/A ) ]

1/4*R [ because R = rho* ( L/A ) ]