Discussion
What happens to the current in a coil while accelerating a magnet inside it ?
Answer: A
The current in the coil increases.
By Faraday's law the induced emf is proportional to the rate of change of flux linkage, \(e = -N\,d\phi/dt\). If the magnet moves through the coil at a steady speed, the flux changes at a steady rate and the emf and current are roughly constant. If the magnet is accelerating, its speed keeps rising, so the flux changes faster and faster and the induced emf, and hence the current in a closed coil, keeps increasing.
The current would decrease if the magnet were slowing down, would be constant at steady speed, and reverses only when the magnet's motion reverses or it passes out of the far end; acceleration in one direction does none of these.
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