A wire of resistivity p(rho symbol) is stretched to double of its length.Find its new resistance and resistivity.
The resistivity of the wire remains unchanged, as it only depends on the material of the wire.
Resistance= Resistivity x length/area
When the wire is stretched to double the length , the area of cross section gets reduced to half.
New Resistance = Resistivity x 2length/area/2
New resistance = (Resistivity x area/length)x4
i.e, New resistance = Resistance x 4