Maximum induced voltage in a coil occurs when:

According to Faraday's Law of Induction, the voltage induced in a coil depends entirely on how quickly the magnetic flux passing through it changes. Since magnetic flux is generated by the current, the induced voltage is highest when that current is changing as rapidly as possible. If the current is steady, such as with a constant DC current, the magnetic field does not change, and zero voltage is induced. Therefore, distractors mentioning DC or the least rate of change are incorrect because no variation means no induction.