A 75-W and 50-W incandescent light bulbs are designed for use with the same voltage.What is the ratio of the resistance of the 75-W bulb to the resistance of the 50-W bulb?
A)1.5
B)0.67
C)2.3
D)0.44
E)3.0

Question

Quizplus · Accepted Answer

The power (P) of a bulb is given by the formula P = V^2/R, where V is the voltage and R is the resistance. Since both bulbs are designed for the same voltage, their power ratio can be inverted to find the resistance ratio. Thus, the resistance ratio of the 75-W bulb to the 50-W bulb is 50/75 = 2/3, which simplifies to 0.67.

A 75-W and 50-W Incandescent Light Bulbs Are Designed for Use