When a bulb marked pz220-40 is connected to a 110 volt circuit, the actual power consumed by the bulb is

When a bulb marked pz220-40 is connected to a 110 volt circuit, the actual power consumed by the bulb is

P = u & # / r because the R of the bulb is constant, the voltage is half of the original, so the power is a quarter of the original, that is 10W