What is the standard SI unit for power measured as joules per second?

The standard SI unit for power, which is defined as the rate at which work is done or energy is transferred, is the watt. One watt is equivalent to one joule per second, meaning that if a device uses one joule of energy in one second, it operates at a power of one watt. This unit is widely used to express power in various contexts, including electrical power, mechanical power, and thermal power.

Other units listed serve different purposes; for example, the volt measures electrical potential difference, the ampere measures electric current, and the joule measures energy. Thus, power expressed in joules per second corresponds specifically to the watt, making it the correct answer for this question.