Q1.A householder was out shopping when her electricity meter reading should have been taken. The electricity company estimated the reading and sent the following bill. Unfortunately, the bill was damaged in the post.
 
(a)     Use the equation in the box to calculate the cost of the electricity used between 12 June and 13 September.
 
 	total cost = number of kilowatt-hours x cost per kilowatt-hour	

Show clearly how you work out your answer.
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Total cost = .............................................................
(2)

(b)     The estimated reading shown on the bill was not very accurate. The correct reading was 53782.
How many kilowatt-hours of electricity had the householder actually used between 12 June and 13 September?
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(2)
(Total 4 marks)

Q2.          (a)     The diagram shows two switches on a room heater. The heater has three power settings. The power produced by two of the settings is given in the table.
 
	Setting	Power in watts	
	Low	700	
	Medium	1400	
	High	 	

(i)      When both switches are on, the heater works at the high power setting.
What is the power of the heater, in kilowatts, when it is switched to the high power setting? 
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                        Power = ......................................................... kilowatts
(1)

(ii)     The heater is used on the high power setting. It is switched on for 1½ hours.
Use the equation in the box to work out the energy transferred from the mains to the heater in 1½ hours.
 
energy transferred    =    power    ×    time	

Show clearly how you work out your answer and give the unit.
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                         Energy transferred = ....................................................
(3)

(iii)    This type of heater is a very efficient device.
What is meant by a device being very efficient?
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(1)

(b)     The graph shows how the temperature of a room changes during the 1½ hours that the heater is used.

After 1 hour, the temperature of the room has become constant, even though the heater is still switched on.
Explain why.
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(2)
(Total 7 marks)

 

Q3.          (a)     The diagram shows the energy transformations produced by a TV.

(i)      Use the information in the diagram and the equation in the box to calculate the efficiency of the TV.
 
efficiency = 	

         Show clearly how you work out your answer.
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Efficiency = ..............................
(2)

(ii)     What eventually happens to the useful energy transferred by the TV?
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(1)

(b)     Electrical appliances left on standby use energy.
          The bar chart shows the power for the appliances that one family leaves on standby when they go on holiday.

          The family is on holiday for a total of 175 hours.

(i)      Use the information in the bar chart and the equation in the box to calculate the energy wasted by leaving the compact stereo on standby while the family is on holiday.
 
energy transferred
(kilowatt-hour, kWh)	=	power
(kilowatt, kW)	×	time
(hour, h)	

         Show clearly how you work out your answer.
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Energy wasted = .............................. kilowatt-hours
(2)

(ii)     Electricity costs 12 p per kilowatt-hour.
         Use the equation in the box to calculate the cost of leaving the compact stereo on standby while the family is on holiday.
 
total cost = number of kilowatt-hours × cost per kilowatt-hour	

         Show clearly how you work out your answer.
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Cost = .............................. p
(1)

(c)     A headline from a recent newspaper article is shown below.
                               
          Explain why leaving appliances on standby damages the environment.
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(2)
(Total 8 marks)

 

Q4.          The diagram shows the direction of heat transfer through a single-glazed window.

(a)     (i)      Name the process by which heat is transferred through the glass.
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(1)

(ii)     Explain how heat is transferred through the glass.
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(2)

(b)     The rate of heat transfer through a window depends on the difference between the inside and outside temperatures.
The graph shows the rate of heat transfer through a 1 m2 single-glazed window for a range of temperature differences.

(i)      What is the range of temperature differences shown in the graph?
From ................................................ to ................................................
(1)

(ii)     A student looks at the graph and concludes:
‘Doubling the temperature difference doubles the rate of heat transfer.’
Use data from the graph to justify the student’s conclusion.
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(2)

(iii)    A house has single-glazed windows. The total area of the windows in the house is 15 m2.
On one particular day, the difference between the inside and outside temperatures is 20 °C.
Use the graph to calculate the total rate of heat transfer through all of the windows on this particular day.
Show clearly how you work out your answer.
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                            Rate of heat transfer = ........................................ J/s
(2)

(c)     A homeowner plans to replace the single-glazed windows in his home with double-glazed windows. He knows that double-glazed windows will reduce his annual energy bills.
The table gives information about the double glazing to be installed by the homeowner.
 
Cost to buy and install	Estimated yearly 
savings on energy bills	Estimated lifetime of the
double-glazed windows	
£5280	£160	30 years	

Explain, in terms of energy savings, why replacing the single-glazed windows with these double-glazed windows is not cost effective.
To gain full marks you must complete a calculation.
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(2)
(Total 10 marks)

 

Q5.          The picture shows one type of solar water heater. Water from the tank is slowly pumped through copper pipes inside the solar panel where the water is heated by energy from the Sun.

(a)     Explain why the copper pipes inside the solar panel are painted black.
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(2)

(b)     Each day the average European family uses 100 kg of hot water.
To kill bacteria, the water going into the tank at 20 °C must be heated to 60 °C.
Calculate the energy needed to increase the temperature of 100 kg of water by 40 °C.
Specific heat capacity of water = 4200 J/kg °C.
Write down the equation you use, and then show clearly how you work out your answer.
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Energy transferred = .................................... J
(2)

(c)     The bar chart shows how the amount of solar energy transferred to the water heater varies throughout the year.
     
How many months each year will there not be enough solar energy to provide the hot water used by an average European family?
.................................................. months
(1)

(d)     In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate.
The water in the tank could be heated by using an electric immersion heater.
Outline the advantages and disadvantages of using solar energy to heat the water rather than using an electric immersion heater.
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(6)
(Total 11 marks)

 

Q6.          (a)     The drawing shows water being heated in a metal saucepan.

(i)      Some energy is transferred from the hotplate to the air by infrared radiation.
What is meant by infrared radiation?
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(1)

(ii)     Explain, in terms of the particles in the metal, how energy is transferred through the base of the saucepan.
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(2)

(b)     Energy is transferred through the water by convection currents.
Explain what happens to cause a convection current in the water.
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(4)
(Total 7 marks)

 

Q7.          (a)     The diagram shows a tray of marbles being shaken from side to side.  As this happens some of the marbles jump out of the tray.

Explain how the tray of marbles is acting as a model for the evaporation of a liquid.
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(2)

(b)     Before giving an injection, a nurse dabs some alcohol onto the patient’s arm. This makes the patient’s skin feel cold.
Explain what happens to make the patient’s skin feel cold.
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(2)

(c)     The graph shows that the molecules in a liquid do not all have the same speed.

Use the information in the graph to explain why a liquid cools down when it evaporates.
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(5)
(Total 9 marks)