Answer
In the United States the bulb consumes 1/4 the power that it does in Europe, and thus appears 1/4 as bright.
Work Step by Step
Use equation 18–6b to calculate the power.
$$P=\frac{V^2}{R}$$
The power is proportional to the square of the voltage. The resistance is the same.
If the voltage is multiplied by one-half (changing from 240 V to 120 V), the power consumed is multiplied by one-fourth.
In the United States the bulb consumes 1/4 the power that it does in Europe, and thus appears 1/4 as bright as a 75-W bulb that is properly designed for 120 V.
