wattseconds

Watt-second is a unit of energy in the International System of Units (SI). It is defined as the amount of energy transferred when one watt of power is sustained for one second. Because power is energy per unit time, a watt-second is mathematically equal to a joule, with 1 W·s = 1 J.

The symbol for the unit is commonly written as Ws or W·s. In most modern contexts, energy is expressed directly in joules, but watt-seconds still appear in some discussions of energy storage or short-duration energy transfer, where both power and time are explicit factors.

Examples help illustrate the concept. A 60-watt light bulb operating for 30 seconds consumes 60 × 30 = 1800 watt-seconds, which is also 1800 joules. A device rated at 100 watts running for 10 seconds uses 100 × 10 = 1000 watt-seconds (1 kilojoule).

Relation to other energy units is straightforward. The energy stored in a battery or capacitor may also be expressed in watt-hours (Wh) or joules. Since 1 Wh equals 3600 J, and 1 W·s equals 1 J, you can convert between these units by appropriate multiplication (for example, 2 Wh equals 7200 W·s).

In summary, watt-seconds are a valid and equivalent unit of energy to the joule, occasionally used in contexts where power and time are discussed together, though joules are typically preferred in contemporary engineering and physics literature.