Which law is used to calculate the magnitude of the electric force between two electric charges?

The $I-V$ graphs of two resistors,and their series combination,are shown below. Which one of these graphs represents the series combination of the other two? Give reasons for your answer.

The quantity of charge flowing past a point multiplied by time is current.

$B_1, B_2$ and $B_3$ are three identical bulbs connected as shown in the figure. When all three bulbs glow,a current of $3\,A$ is recorded by the ammeter $A$.
$(i)$ What happens to the glow of the other two bulbs when the bulb $B_1$ gets fused?
$(ii)$ What happens to the reading of $A_1, A_2, A_3$ and $A$ when the bulb $B_2$ gets fused?
$(iii)$ How much power is dissipated in the circuit when all three bulbs glow together?

Name the device/instrument used to measure potential difference. How is it connected in an electric circuit?

How much work is to be done in moving a charge of $2 \, C$ through an electric potential difference of $6 \, V$ (in $, J$)?