Q$3$: The electric field in a parallel plate capacitor is given by $E=\frac{V}{d}.$ Plot approximate graph between $E$ and $d$ while $V$ is constant.

$[5$ marks$]$

Q$4$: The capacitance of a parallel plate capacitor is given by the equation:

$[5$ marks$]$

$c=lon\frac{S}{d}$

What happens to the capacitance when a material is used instead of air as an insulator between the plates $($having ${}_r>1)?$