Question

Find the energy in joules consumed in 10 hours by four devices of power 500 W each.

Answer 1

The power of four devices = $4×500\ W = 2000\ W$
Time = $10$ hours
Therefore,
The energy consumed = power × time
= $2000×10\ Wh$
= $20000\ Wh$
= $20\ kWh$
= $20\ units$ [$1\ \text {unit} = 1\ kWh$]