A 100-W bulb and a 40-W bulb,each designed for an applied voltage of 120 V,are connected in series across a 120-V source.What are the voltages across the 100-W bulb and across the 40-W bulb?
A) 86 V,34 V
B) 30 V,90 V
C) 90 V,30 V
D) 34 V,86 V

Question

Quizplus · Accepted Answer

When bulbs are in series, they have the same current. The resistance of each bulb can be calculated using R = V^2/P. The 100-W bulb has a resistance of 144 ohms, and the 40-W bulb has a resistance of 360 ohms. The voltage across each bulb is proportional to its resistance. Therefore, the voltage across the 100-W bulb is 34 V, and across the 40-W bulb is 86 V.

A 100-W Bulb and a 40-W Bulb,each Designed for an Applied