A copper wire that is straight and has a diameter of $0.42 \times 10^{-3}\,\text{m}$ contains free electrons with a number density of $8.5 \times 10^{28}\,\text{m}^{-3}$. During one time interval, a charge of $0.15\,\text{C}$ passes along the wire. What is the mean displacement of the free electrons along the wire over this time interval?
- A$3.3 \times 10^{-8}\,\text{m}$
- B$2.0 \times 10^{-5}\,\text{m}$
- C$8.0 \times 10^{-5}\,\text{m}$
- D$2.5 \times 10^{-4}\,\text{m}$