Which of the following is NOT a basic electrical unit in the SI metric system?

Horsepower is not a basic electrical unit in the SI metric system, making it the correct answer to the question. In contrast, the volt, joule, and watt are all fundamental units used to measure electrical concepts.

The volt is the unit for electric potential or voltage, which quantifies the potential difference that drives electric current through a circuit. The joule is the unit for energy, equivalent to the work done when a one-ampere current passes through a resistance of one ohm for one second. The watt measures electrical power, representing the rate at which energy is transferred or consumed, and is defined as one joule per second.

Horsepower, however, originates from imperial measurements and is primarily used to measure mechanical power, not directly linked to electrical units in the SI system. Therefore, highlighting horsepower as the non-basic electrical unit clarifies its distinction from the foundational terms governing electrical engineering topics.