GCSE Physics

kWh Costs Question

Look at the table of data below. For the hairdryer, notice that both power and time aren't always in the "expected" units of kW and h.

ObjectPowerTime usedUnits used (kWh)Cost (p)
hairdryer1·2 kW30 minutes0·64·8 p
light bulb100 W20 hours  
microwave oven800 W45 minutes  
Assume 1 kWh of energy costs 8 p

For the hairdryer, remember that 60 minutes = 1 hour, so 30 minutes = 0·5 hours. We must use this to find the units (kWh) used.

See if you can work out the units used, and the cost of running, the light bulb and microwave oven.

Hints | Answers

GCSE PhysicsEnergy Menu  GCSE PhysicsElectricity Menu