Two small charged metal spheres A and B are placed in a vacuum. Their centres are separated by $12.0\,\text{cm}$, as shown in Fig. 4.1. It may be assumed that the charge on each sphere acts as a point charge at the centre of the sphere. Point P is a movable point on the line joining the centres of the spheres, at a distance $x$ from the centre of sphere A. Fig. 4.2 shows how the electric field strength $E$ at point P varies with distance $x$.
(a(i))[1]
State the evidence provided by Fig. 4.2 for the statement that the spheres are conductors.
(a(ii))[2]
State the evidence provided by Fig. 4.2 for the statement that the charges on the spheres are either both positive or both negative.
(b(i))[1]
State the relation between electric field strength $E$ and potential gradient at a point.
(b(ii).1)[2]
Use Fig. 4.2 to state and explain the distance $x$ at which the rate of change of potential with distance is maximum.
(b(ii).2)[2]
Use Fig. 4.2 to state and explain the distance $x$ at which the rate of change of potential with distance is minimum.
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Electric field strength inside spheres is zero” …