Question

If the length of a conductor is doubled and area is halved, then how will the resistance of the conductor changes.

Answer 1

Resistance when length is $l$ and area is $A$ is $R_1=\rho l/A$

Now new length is $2l$ and area is $A/2$ so new resistance will be

$R_2=\rho \frac{2l}{A/2}=\rho 4l/A=4R_1$

So resistance becomes 4 times.