Question

when using alternating current in the u.s., how many times a second does the polarity change? 60 80 100 120

Explanation:

In the U.S., the standard frequency of alternating current (AC) is \(60\) Hz. One cycle of AC involves two polarity changes (from positive to negative and then back to positive). So, if the frequency \(f = 60\) Hz (cycles per second), the number of polarity changes per second is \(2f\).

Answer:

\(120\)