Question

Express 20 Wh of energy in S.I. units.

Answer 1

The SI unit of energy is the joule (J).

Since $$1\text{ Wh} = 1\text{ W} \times 1\text{ h} = 3600\text{ J}$$

$$20\text{ Wh} = 20 \times 3600 = 72000\text{ J} = 7.2 \times 10^{4}\text{ J}$$