A variable inductor can be placed in series with a light bulb to act as a dimmer.

Question:

A variable inductor can be placed in series with a light bulb to act as a dimmer.
(a) What inductance would reduce the current through a 100-W light bulb to 75% of its maximum value? Assume a 120-V rms, 60-Hz source.
(b) Could a variable resistor be used in place of the variable inductor to reduce the current? Why is the inductor a much better choice for a dimmer?