1.4 Cost of electricity

A kettle has a power of 2500 W. What's the power in kW?

• 250 kW

• 2.5 kW

• 25 kW

• 0.25 kW

A kettle has a power of 2.5 kW, how much energy is used if it takes 1 minute to boil the water inside?

(Energy in joules = Power in watts x Time in seconds)

• 2.5 J

• 150 000 J

• 2500 J

• 150 J

If a 4 kW oven was on for 2h cooking a joint of beef, how many units (kWh) of electrical energy were used?

• 8 kWh

• 4 kWh

• 2 kWh

• 0.5 kWh

If the oven used 8kWh of electrical energy and each kWh was 34p, calculate the cost.

• 272 p

• £272

• 2.72 p

• £27.20

How many units (kWh) does a 45 W light bulb use if left on all day and night?

• 1.08

• 10.8

• 45

• 1080

Gloria is worried. She left the heater on in her room from 8 a.m. to 4 p.m. It is a 2kW heater. If the electricity cost 30 p per unit, how much did her mistake add to the family electricity bill (in pence)?

• 480
• 48

• 360

• 240

Which of the following appliances costs more to run?

• 3kW Cooker for 2h

• 200W PlayStation for 12h

• 10 x 50W light bulbs for 6h

• 850W Washing machine for 3h

How much does it cost to use a 2000 W electric fire for 45 min if electricity costs 34p pence per unit? (in pence)

• 51
• 68

• 34

• 102