Final answer:
The compound unit equivalent to a watt times a second is a joule, which represents the total energy used as power multiplied by time.
Step-by-step explanation:
The compound unit equivalent to a watt times a second is a joule. A watt (W) is a unit of power, which is defined as energy per unit time, specifically one joule per second (1 W = 1 J/s). When you multiply a watt by a second, you get the unit for energy, since power is the rate at which energy is expended (P = E/t, so E = Pt). Therefore, multiplying the power (in watts) by time (in seconds) gives you the total energy used in that time, which is measured in joules.
For example, if a device runs at 10 watts for 2 seconds, it will have used 20 joules of energy (10 W * 2 s = 20 J).