$A$ conducting wire offers resistance to the flow of electrons because electrons repel each other in the wire.

Define resistivity of a material.

$A$ wire of length $L$ and resistance $R$ is stretched so that the length is doubled and area of cross-section is halved. How will its
$(a)$ resistance change?
$(b)$ resistivity change?

If the diameter of a conducting wire is doubled,how many times does its resistance become?

$Ohm's$ law is a relation between the power used in a circuit to the current and the potential difference.

State $Ohm's$ law. Calculate the resistance of a conductor,if the current flowing through it is $0.2 \, A$ when the applied potential difference is $0.8 \, V$.