If the area of cross-section of a resistance wire is halved, then its resistance becomes :

When the area of cross-section of a conductor is doubled, its resistance becomes:

The resistivity of copper metal depends on only one of the following factors. This factor is :

A piece of wire of resistance 20 Ω is drawn out so that its length is increased to twice its original length. Calculate the resistance of the wire in the new situation.

The electrical resistivities of three materials P, Q and R are given below :

P 2.3 x 10³ Ω m

Q 2.63 x 10^-8 Ω m

R 1.0 x 10¹⁵ Ω m

Which material will you use making (a) electric wires (b) handle for soldering iron, and (c) solar cells? Give reasons for your choices.