A bulb is designed for 100 W at 130 V rms.What is the power dissipated by this bulb if it is used in a 120 V rms circuit?
A) 169 W
B) 130 W
C) 100 W
D) 85.0 W
E) it will blow out

Question

Quizplus · Accepted Answer

The power dissipated by the bulb can be calculated using the formula:

P = V^2/R

Where P is the power, V is the voltage, and R is the resistance of the bulb.

From the given information, we know that the bulb is designed for 100 W at 130 V rms. Using this, we can find the resistance of the bulb as:

R = (V^2)/P = (130^2)/100 = 169 Ω

If the bulb is used in a 120 V rms circuit, then the power dissipated by the bulb can be calculated as:

P = (120^2)/169 = 84.9 W

Therefore, the best choice is D, 85.0 W (rounded off to 2 significant figures).

A Bulb Is Designed for 100 W at 130 V