Which of the following is not a unit of energy?

The distinction lies in the definitions and units of the various terms related to energy and electrical measurements. Ohm is a unit of electrical resistance, not energy. It measures how much a material resists the flow of electric current.

On the other hand, Joule, Watt, and Volt are all related to energy in different ways. Joules are the standard unit of energy in the International System of Units (SI), whereas Watts are a measurement of power that indicates the rate at which energy is used or generated. Specifically, one watt is equivalent to one joule per second. Volts, meanwhile, measure electric potential or voltage, which is related to the energy per charge in an electric circuit.

Thus, while Joules, Watts, and Volts all have direct implications in the context of energy, the Ohm stands apart as a unit of resistance, making it the correct choice as the one that is not a unit of energy.