To measure the frequency of an electrical signal, the appropriate tool would be a?

A frequency meter is specifically designed to measure the frequency of an electrical signal. It works by counting the number of cycles of the signal that occur in a given time period, typically expressed in hertz (Hz). This makes it the most accurate tool for determining the frequency of electrical signals.

An oscilloscope is capable of displaying the waveforms of electrical signals, allowing you to visualize their frequency, but it requires additional calculations or interpretation to determine the frequency from the waveform. While it is a versatile tool for many aspects of signal analysis, it is not dedicated solely to measuring frequency.

An ammeter measures current (in amperes) flowing through a circuit, which does not provide information about frequency. Similarly, a wattmeter measures electrical power (in watts) and is not designed to gauge frequency either.

Therefore, when the goal is to specifically measure frequency, using a frequency meter is the most direct and reliable choice.