Mains electricity | Exit Quiz | Oak National Academy

Which of the following is the unit of power?

• ohms

• volts

• amps

• watts

• joules

Answer explanation

Power is measured in watts.

Which of the following devices or appliances has the greatest power rating?

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• 
• 

Answer explanation

The device or appliance which has the greatest power rating is the toaster with a maximum power of 1050 W.

How many watts are there in a kilowatt?

• a thousandth watts

• a thousand watts

• a million watts

• a billion watts

Answer explanation

A kilowatt is equal to a thousand watts; 1 kW = 1000 W.

Which of the following values is equal to 0.1 kilowatts?

• 1 watt

• 10 watts

• 100 watts

• 1000 watts

Answer explanation

0.1 kilowatts is equal to 0.1 × 1000 = 100 watts.

How many watts are there in a gigawatt?

• 100

• 1000

• 1 000 000

• 1 000 000 000

Answer explanation

A gigawatts is equal to a billion watts; 1 GW = 1 000 000 000 W.

What is the cost of using a 1000 W heater for 30 min, if 1 kWh costs £0.30?

• 3 pence

• 15 pence

• 30 pence

• 60 pence

Answer explanation

The number of kWh is: 1 kW × 0.5 hr = 0.5 kWh. 0.5 kWh × 30 pence = 15 pence.