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

Given,

Power rating (P) = 500 W

Converting W into kW

1000 W = 1 kW

500 W = $\dfrac{500}{1000}$ = 0.5 kW

Time (T) = 10 h

We know,

Power = $\dfrac{\text{Energy consumed}}{\text{Time taken}}$

Or

Energy consumed by each device = Power x Time taken

Substituting we get,

Energy consumed by each device = 0.5 x 10 = 5 kWh

Energy consumed by four devices = 4 x 5 = 20 kWh

Converting kWh to J

1 kWh = 3.6 x 10⁶ J

So, 20 kWh = 3.6 x 10⁶ x 20 = 7.2 x 10⁷ J

Hence, the energy consumed = 7.2 x 10⁷ J