Which of the following quantities cannot be measured using a multi-meter?

A multi-meter is a versatile instrument primarily used for measuring electrical quantities such as voltage, current, and resistance. However, it does have limitations when it comes to certain measurements.

Power factor is defined as the ratio of real power (watts) to apparent power (volt-amperes) in an AC electrical system. While a multi-meter can measure voltage and current, it does not directly assess the phase relationships between the voltage and current waveforms required to calculate power factor. To accurately measure power factor, specialized devices like power meters or power analyzers are used, which can analyze the waveform and calculate the phase difference.

In contrast, a multi-meter is fully capable of measuring voltage (the potential difference across components), current (the flow of electric charge), and resistance (how much a device opposes the flow of electric current). It is equipped to display these values directly or through calculations based on Ohm's Law.

Understanding these distinctions helps clarify why power factor measurement falls outside the standard capabilities of a multi-meter, making it essential for users to select appropriate instruments tailored to their measurement needs.