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Questions on Energy Transitions

Q14. The photos below show the boxes for two household appliances: a small electric hot plate ring and a games console.

(a) What is the power rating of each of the appliances?

Hot plate: 1000W or 1 kW

Games console: 90W (minimum) and 150W (maximum)

The power rating depends on the action of some appliances - some activities require more energy than others. The range shows how much power is converted when the appliance is idle to when it is working at maximum capacity.

(2 marks)

(b) Calculate how many units of electricity (kWh) are used if the hot plate ring is switched on for two hours to cook a stew.

(3 marks)

Number of electricity units = power in kW x time in hours

= 1 x 2

= 2 kWh (or 2 units of electricity)

(c) Calculate how much it costs to cook the stew if electricity costs 11p per unit.

Cost = number of kWh x cost per kWh

= 2 x 11 = 11p

(2 marks)

(d) Playing on a Games Console is great fun. Calculate the maximum annual costs for your parents in electricity if you play on the playstation for an average of 2 hours and 30 minutes every day. (Assume it is not a leap year).

Number of hours = 2.5 x 365 = 912.5

Maximum Power in kW = 0.150

Number of kWh = 912.5 x 0.150 = 136.875

Cost = 136.875 x 11p = 1506p

= £15-06

(3 marks)

(Total 10 marks)