(a)[2]
Define the electric potential at a point.
(b(i))[2]
Show that, when $x = 10\,\text{pm}$, the electric potential $V$ at point P is $130\,\text{V}$.
(b(ii))[2]
Calculate $V$ when $x = 30\,\text{pm}$, giving your answer to two significant figures.
(b(iii))[1]
On Fig. 5.1, place a cross (\times) at a point, other than infinity, where the electric potential is zero.
(b(iv))[3]
On Fig. 5.2, sketch how $V$ varies with $x$ between $x = 10\,\text{pm}$ and $x = 110\,\text{pm}$.