(a)[1]
The current in a filament lamp becomes smaller. State and explain what happens to the lamp’s resistance.
(b(i))[1]
A cylindrical wire of length $L$ has resistance $R$. Inside the wire’s volume there are $N$ free electrons (charge carriers) altogether. Each free electron carries charge $e$. The potential difference across the ends of the wire is $V$. Find an expression for the current in the wire, using some or all of $e$, $L$, $N$, $R$ and $V$.
(b(ii))[2]
Find an expression for the mean drift speed of the free electrons.
(b(iii))[1]
Find an expression for the mean time needed for a free electron to travel the complete length of the wire.