Physics 9702 · AS & A Level · Electric current

Electric current — practice question

In copper wire X, which has radius $5.0 \times 10^{-5}\,\text{m}$, free electrons move along the wire with an average drift speed of $2.8 \times 10^{-2}\,\text{m s}^{-1}$. The current in this wire is $3.0\,\text{A}$. Copper wire Y has a current of $2.0\,\text{A}$ and a radius of $1.0 \times 10^{-4}\,\text{m}$. What is the average drift speed of the free electrons in copper wire Y?

  • A$4.7 \times 10^{-3}\,\text{m s}^{-1}$
  • B$9.3 \times 10^{-3}\,\text{m s}^{-1}$
  • C$1.1 \times 10^{-2}\,\text{m s}^{-1}$
  • D$1.9 \times 10^{-2}\,\text{m s}^{-1}$

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