Define electrostatic potential at a point.

Write the mathematical expression for electric potential.

What is the other name of the commercial unit of electrical energy?

Two identical resistors,each of resistance $2 \Omega$,are connected in turn: $(i)$ in series,and $(ii)$ in parallel to a battery of $12 \text{ V}$. Calculate the ratio of power consumed in the two cases.

How can we measure the potential difference across the ends of a conductor?

$A$ potential difference $V$ is applied across a conductor of length $L$ and diameter $D$. How is the resistance $R$ of the conductor affected,when in turn $(i)$ $V$ is halved,$(ii)$ $L$ is halved,and $(iii)$ $D$ is doubled? Justify your answer in each case.