What is measured in hertz?

Hertz is the unit of measurement for frequency, which specifically indicates the number of cycles or reversals that occur within a second. In the context of electrical systems, this often refers to the alternating current (AC) frequency, which is how many times the current switches direction in a given time frame.

In the case of option C, it correctly asserts that hertz measures the rate at which reversal occurs, which is particularly relevant when discussing AC electricity. For instance, in many regions, standard household electricity operates at 60 hertz, meaning that the electrical current alternates direction 60 times each second.

The other options do not pertain to frequency measurements. Resistance in a conductor relates to the opposition to current flow and is measured in ohms. The flow of current is measured in amperes, which quantifies the rate of electron flow. Voltage delivery rate, while related to the flow of electricity, is measured in volts and indicates the potential difference that drives the current through a circuit.

Thus, option C is the only choice that correctly aligns with the definition of hertz in the context of electrical measurements.