(a)[1]
Demonstrate that the free-electron number density in the wire is $8.5 \times 10^{28}\,\text{m}^{-3}$.
(b)[3]
Calculate the mean drift speed of the free electrons. Express your answer in $\text{m s}^{-1}$.
Physics 9702 · AS & A Level · Electric current
Electric current — practice question
In a circuit, a metal wire measures $1.8\,\text{m}$ in length and has a cross-sectional area of $1.5 \times 10^{-6}\,\text{m}^2$. The wire contains a total of $2.3 \times 10^{23}$ free electrons (charge carriers). A current flows in the wire so that $172\,\text{C}$ of charge passes a fixed point during $2.5$ minutes.
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