Julia produces a 2 mA current by moving the south pole of a bar magnet into a solenoid. The solenoid contains 150 loops of wire. Which change should Julia make to generate a larger current?

A changing magnetic field induces a current in the solenoid. The induced voltage—and therefore the current—gets larger when the coil has more turns, because the magnetic effect is linked through more loops. So Julia should use more loops of wire in the coil. Setting the magnet down or moving it slower would reduce the change in magnetic field over time; using the north pole instead would reverse the current’s direction, not necessarily increase its size.

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