Question

if a wire of resistance R is melted and recast to half of its lenght then new resistence of the wire will be

Answer 1

resistance is proportional to (L/A)

A1L1 =A2L2(as volume is same)

or, AL  =A2 (L/2)

or, A2 = 2*A

new resistance = (L/2)/(2A) = L/(4*A) =R/4