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GCSE Standard Questions: Electricity in the Home

Q17. John uses four electrical appliances for different lengths of time.

Look at the table below.

Appliance
Power (W)
Time used (hours)
Energy = Pt (kWh)
Hair dryer
1500
0.3
0.450
TV
100
5
0.500
Toaster
2000
0.2
0.400
Light bulb
10
12
0.120

 

(a)

(i) Which appliance uses the most energy?

Energy is the product of the power rating and time used - energy companies use kWh so I have calculated the kWh for each - but to compare in an exam you could just use the raw Wh value...

The TV

[1 mark]

(ii) Which appliance has cost the least to use?

The light bulb

[1 mark]

(b) Three electrical circuit components that are used in domestic appliances are the thermistor, variable resistor and LDR

Which of the components would be used in the following situations:

(i) Monitoring the position of a door variable resistor

(ii) Turning on lights when it gets dark LDR

(iii) Operating a heating system thermistor

if all correct if one correct

[2 marks]

(c) A charge of 44 kC flows through a light bulb.

The potential difference across the bulb is 230V.

Calculate the energy transferred, giving your answer to 2 significant figures.

P = IV

E/t = Q/t x V

E = QV

E = 44,000 x 230

E = 10,120,000 J

E = 10,000,000 J (or 10 MJ)

[4 marks]

(Total 8 marks)