One watt is equal to?

• A. One joule of work per second
• B. One joule of work per minute
• C. One kilojoule per second
• D. One joule per hour

Answer: (A)

Power is the rate at which work is done or energy is transferred. A watt is defined as one joule of energy transferred every second, so one watt means energy of one joule is used each second. The other options describe different rates: one joule per minute is much smaller (about 0.0167 watts), one kilojoule per second would be 1000 watts, and one joule per hour is extremely small (about 0.00028 watts). So the statement that matches the definition is that one watt equals one joule per second.