In europe the standard voltage in homes is 220 v instead of the 120 v used in the united states. therefore a "100-w" european bulb would be intended for use with a 220-v potential difference (see problem 25.40). (a) if you bring a "100-w" european bulb home to the united states, what should be its u. s. power rating? (b) how much current will the 100-w european bulb draw in normal use in the united states?

a) The US power rating for the european bulb must be 27.27 W

b) The current in the United Stated for the european bulb is 0.227A

Explanation:

First of all the bulb is not going to light in 120V like it does in 220V, the bright is going to be much lower (near 1/4). Now, lets take a look on a circuit perspective:

The bulb in a circuit is modeled like a simple resistor, so we have a resistor conected to a voltage source, see figure 1. There we have a current given by:

Where is the 220v Input voltage, R is the resistance from the bulb. In the problem we have the power consumption in watts given by:

Clearing

Now, from ohm's law

So 484 ohm is the resistance from the bulb.

Now in the circuit lets replace the voltage source from 220v to 120v and lets calculate the current, and the power consuptiom

And the power consuptiom: