(a)[2]
State the meanings of the symbols $A$ and $n$. $A:$ $n:$
(b)[2]
Use the expression above to find the SI base units of $e$. Show your working.
(c)[2]
Two lamps P and Q are joined in series to a battery, as illustrated in Fig. 6.1. The radius of the filament wire in lamp P is twice the radius of the filament wire in lamp Q. The filament wires are made from metals with the same value of $n$. Calculate the ratio $\dfrac{\text{average drift speed of free electrons in filament wire of P}}{\text{average drift speed of free electrons in filament wire of Q}}$.