A small piece of metal wire is dragged across the gap between the pole pieces of a magnet in 0.5 s. The magnetic flux between the pieces is 8 × 10−4 Wb. The induced emf in the wire is:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 1.6 mV
By Faraday’s law, the average emf induced equals the rate of change of magnetic flux. As the wire is dragged across the gap it cuts all the flux lines between the pole pieces, 8 × 10−4 Wb, in 0.5 s.
\( \displaystyle |\varepsilon| = \frac{\Delta\Phi}{\Delta t} \)
\( \displaystyle |\varepsilon| = \frac{8\times10^{-4}\,\mathrm{Wb}}{0.5\,\mathrm{s}} \)
\( \displaystyle |\varepsilon| = 1.6\times10^{-3}\,\mathrm{V} = 1.6\,\mathrm{mV} \)