Usually, how many volts does it take to power a 40 watt light bulb?

Question

anonymous · Answer

Watt is a measure of power. Electrical power for elements in a DC circuit is defined as$$P = IV $$We need to know current being drawn by the lightbulb. If we know the resistance of the lightbulb, from Ohm's Law, we can express power as$$P = {V^2 \over R}$$

This problem is undefined as is.

anonymous · Answer

Eashmore is right we when talking about power of anything in electrical system means independent of voltage and current, so the resistance decided the current from the source feeding a constant voltage. and the product in DC will be power. and in AC one more factor is added which is known as power factor