What does frequency measure in an AC circuit?

Frequency in an AC circuit measures the number of cycles of the waveform that occur in one second. This is expressed in hertz (Hz), with one hertz equal to one cycle per second. In an alternating current (AC) system, the voltage and current change direction periodically, and frequency is crucial for determining how quickly these changes occur.

Understanding frequency is important for various applications, such as ensuring that electrical devices are compatible with the AC supply they are connected to, as different devices may operate optimally at specific frequencies. For example, in many countries, the standard frequency for household AC is either 50 Hz or 60 Hz.

The other options focus on different aspects of an AC circuit: total resistance relates to the opposition to current flow, current supplied indicates how much electric charge is flowing, and voltage level pertains to the potential difference driving the current. While all these factors play a role in AC circuitry, frequency specifically refers to the rate of oscillation of the current.