(a)[2]
The current $I$ in a metal wire is represented by $I = Anve$. State what the symbols $A$ and $n$ represent.
(b)[2]
The diameter of a wire $XY$ changes linearly with distance along the wire, as shown in Fig. 7.1. A current $I$ flows in the wire. At end $X$, the diameter is $d$ and the mean drift speed of the free electrons is $v_x$. At end $Y$, the diameter is $\frac{d}{2}$. On Fig. 7.2, sketch a graph showing how the mean drift speed varies with position along the wire from $X$ to $Y$.