Efficiency and Energy – Practice Exam Questions
1.	The diagram below shows a 60 watt electric light bulb.
(a)	60 W means that 60 joules of energy are transferred into the bulb each second.   In use, how much energy is given out by the bulb each second?					(1)
(b)	Describe the energy transfers which occur as it is used:
___________ energy is transferred into ___________ energy  and ______________ energy.	(2)
(c)	Some of the energy given out is wasted.  Why is some of the energy wasted?		(1)
2.	(a)	In Britain most power stations burn fuel to produce heat. The diagram shows the stages by which the heat is transferred into electrical energy.  Complete the diagram by filling in the missing word.
Water heated to produce steam	®	Steam turns a turbine	®	Turbine turns a 
__________	®	Electricity is
produced	
														  (1)

(b)	A fuel burning power station uses 2000 joules of fuel energy to generate 600 joules of electrical energy. The rest of the fuel energy is wasted as heat.
(i)	For every 600 joules of electrical energy generated, how much fuel energy is wasted as heat?	(1)
(ii)	Use the following equation to calculate the efficiency of the power station.  Show clearly how you work out your answer.
					efficiency =  				(2)
3.	Complete the following sentences.								(4)
	A TV set is designed to transfer electrical energy into __________  energy and __________ energy.
	A hair dryer is designed to transfer electrical energy into ___________ energy and _________ energy.

4.	The diagram below shows four stages in the production of electricity by a coal-fired power station.

(a)	Some data for Didcot coal-fired power station is given below.					(8)
	Number of generators	4
	Maximum continuous power rating of a generator	500 MW at 23 500 V
	Energy content of coal used	2.66 × 1010 J per tonne
	Total quantity of coal used each day	18 289 tonnes
	Use the given data to calculate:
(i)	the total electrical energy output each day.  						J/day
(ii)	the total input of chemical energy from the coal each day.					J/day
(iii)	the efficiency of the power station.					_____________ %