A lightbulb is connected to a 120 V (rms), 60 Hz source. How many times per second does the current reverse directions?
A) 60
B) 130
C) 120
D) 30

Question

Quizplus · Accepted Answer

In an AC circuit, the current changes direction as the voltage changes polarity. The frequency of an AC circuit is the number of cycles (or complete changes in direction) that the voltage (and current) complete in one second. Since the problem states that the source is a 60 Hz source, this means that the voltage (and current) complete 60 complete cycles of change in direction per second. Since one cycle involves two changes in direction (from positive to negative and back to positive again), the current changes direction 120 times per second (2 times per cycle * 60 cycles per second = 120 changes in direction per second). Therefore, the correct answer is C) 120.

A Lightbulb Is Connected to a 120 V (Rms), 60