If the magnetic flux through a coil of 1200 turns increases from zero to \( 5.4\times10^{-5}\,\mathrm{Wb} \) in 2.7 ms, what is the magnitude of the induced emf during this time
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 24 V
By Faraday’s law the magnitude of the emf induced in a coil of N turns is N times the rate of change of the flux through one turn.
\( \displaystyle |\varepsilon| = N\,\frac{\Delta\phi}{\Delta t} \)
The time is \( 2.7\,\mathrm{ms} = 2.7\times10^{-3}\,\mathrm{s} \).
\( \displaystyle |\varepsilon| = 1200\times\frac{5.4\times10^{-5}}{2.7\times10^{-3}} = 1200\times0.02 = 24\,\mathrm{V} \)