name: p2 electricity - immanuel college, bradforda student plugs all four of the appliances into one...

P2 ELECTRICITYQuestion Practice

Name: ________________________

Class: ________________________

Date: ________________________

Time: 199 minutes

Marks: 196 marks

Comments: HIGHER TIER

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Figure 1 shows a circuit diagram containing two identical lamps arranged in parallel.

The reading on the ammeter is 186 mA.

Figure 1

(a) Which statement about the current through the lamps is true?

Tick one box.

The current through both lamp P and lamp Q is 0.093 A




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(b) One of the lamps breaks and is not replaced.

Which statement about the current in the other lamp is true?

Tick one box.

The current through the lamp is 0.093 A




(1)

(c) Figure 2 shows a circuit that can be used to alter the brightness of a lamp.

Figure 2

The resistance of the variable resistor is increased.

What effect will this have on the brightness of the lamp?

Explain your answer.

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(2)

(d) When the potential difference across the lamp is 3.3 V, the current is 0.15 A.

Write down the equation that links current, potential difference and resistance.

Equation ___________________________________________________________

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(e) Calculate the resistance of the lamp.

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Resistance = __________________ Ω(3)

(f) Sketch a current–potential difference graph for a filament lamp.

(1)

(Total 9 marks)

An electric current is a flow of electrical charge through a circuit.

(a) Complete the sentence.

Use a word from the box.

atoms electrons ions molecules

Metals are good conductors of electricity because electrical charge is transferred

by delocalised __________________________

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(b) Draw one line from each symbol to the name of the component.

Standard symbol Name of component

(3)

(c) The table below shows information about some electrical appliances.

Electrical appliance Power in watts

Hairdryer

1500

Kettle

2500

Electric hob

3000

Television

360

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A student plugs all four of the appliances into one multi-way socket.

The mains electricity is 230 V.

The highest safe current in the socket is 30 A.

Explain why it is not safe to use all four appliances at the same time.

In your answer you should:

• calculate the total power needed

• use the equation

current = power ÷ potential difference

to calculate the total current needed.

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(d) The figure below shows how electrical power is transferred from power stations toconsumers using the National Grid.

Transformer 1 is a step-up transformer.

Explain why step-up transformers are used in the National Grid.

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(3)

(e) What is the purpose of Transformer 2?

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(1)

(f) In a power station 900 MJ of thermal energy were released by burning natural gas.

Write down the equation that links efficiency, useful input energy transfer and useful outputenergy transfer.

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(g) In a power station 900 MJ of thermal energy were released by burning natural gas.

Only 405 MJ was generated.

Calculate the efficiency of this energy transfer.

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Efficiency = _________________

(2)

(Total 15 marks)

A student used electrical circuits to investigate the relationship between resistance, potentialdifference and current.

Figure 1 shows how the student connects the first circuit he set up.

Figure 1

(a) The circuit does not work.

Draw the correct circuit.

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(b) The student then sets up the circuit correctly.

Look at Figure 2.

Figure 2

What is the reading on the voltmeter?

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(1)

(c) The student then set up a circuit to investigate how resistance affects the brightness of alamp.

Figure 3 shows the circuit he set up.

Figure 3

The student increases the resistance of the variable resistor.

What effect does this have on the brightness of the lamp?


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(d) Write down the equation that links current, potential difference and resistance.

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(1)

(e) When the potential difference across the lamp is 3.3 V the current is 0.15 A.

Calculate the resistance of the lamp in the student’s experiment.

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Resistance = _________________ Ω(3)

(Total 9 marks)

A student finds some information about energy-saving light bulbs.

(a) A 30W light bulb uses 600J of electrical energy in a certain period of time. In that time, itproduces 450 J of light energy. The rest of the energy is wasted.

(i) Calculate the energy wasted by the light bulb in this period of time.

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Wasted energy = _________________ J

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(ii) What happens to the energy wasted by the light bulb?

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(1)

(iii) Calculate the efficiency of this light bulb.

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Efficiency = ______________________________

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(iv) Calculate the period of time, in seconds, during which the 600 J is provided to the30 W light bulb.

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Time = _____________ s

(2)

(b) A company that makes light bulbs provides information about some of their products.

The table shows some of this information.

Power in watts Lifetime in hours Cost of bulb in £

Filament bulb 60 1250 2.00

LED bulb 12 50 000 16.00

(i) Suggest why it is important to confirm this information independently.

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(1)

(ii) A homeowner is thinking about replacing his filament bulbs with LED bulbs.

A 12 W LED bulb gives the same light output as a 60 W filament bulb.

Suggest reasons why the homeowner is likely to choose LED bulbs.

Use the information given in the table.

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(2)

(iii) State one factor, other than efficiency, that is important when considering the choiceof a bulb for lighting in the home.

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(1)

(Total 10 marks)

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Electricity can be generated using various energy sources.

(a) Give one advantage and one disadvantage of using nuclear power stations rather thangas-fired power stations to generate electricity.

Advantage __________________________________________________________

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Disadvantage _______________________________________________________

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(b) (i) A single wind turbine has a maximum power output of 2 000 000 W.

The wind turbine operated continuously at maximum power for 6 hours.

Calculate the energy output in kilowatt-hours of the wind turbine.

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Energy output = ____________________ kWh

(2)

(ii) Why, on average, do wind turbines operate at maximum power output for only 30% ofthe time?

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(1)

(c) An on-shore wind farm is made up of many individual wind turbines.

They are connected to the National Grid using underground power cables.

Give one advantage of using underground power cables rather than overhead powercables.

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(1)

(Total 6 marks)

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(a) Iceland is a country that generates nearly all of its electricity from renewable sources.

In 2013, about 80% of Iceland’s electricity was generated using hydroelectric powerstations (HEP).

Describe how electricity is generated in a hydroelectric power station. Include the usefulenergy transfers taking place.

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(b) The UK produces most of its electricity from fossil fuels.

Many people in the UK leave their televisions in ‘stand by’ mode when not in use, insteadof switching them off.

It is better for the environment if people switch off their televisions, instead of leaving themin ‘stand by’ mode.

Explain why.

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(c) A scientist wrote in a newspaper:

‘Appliances that do not automatically switch off when they are not being used should bebanned.’

Suggest why scientists alone cannot make the decision to ban these appliances.

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(1)

(Total 8 marks)

Electrical circuits have resistance.

(a) Draw a ring around the correct answer to complete the sentence.

When the resistance of a circuit increases, the current in the circuit

decreases.

increases.

stays the same.

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(b) Use the correct answer from the box to complete each sentence.

a filament bulb an LED an LDR

An electrical component which has a resistance that increases as the

temperature increases is _________________________ .

An electrical component which emits light only when a current flows through it

in the forward direction is _________________________ .

(2)

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(c) When some metals are heated the resistance of the metal changes.

The equipment for investigating how the resistance of a metal changes when it is heated isshown in the diagram.

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In this question you will be assessed on using good English, organising information clearlyand using specialist terms where appropriate.

Describe an investigation a student could do to find how the resistance of a metal samplevaries with temperature. The student uses the equipment shown.

Include in your answer:

• how the student should use the equipment

• the measurements the student should make

• how the student should use these measurements to determine the resistance

• how to make sure the results are valid.

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(d) The table shows some data for samples of four metals P, Q, R and S.

The metal samples all had the same cross-sectional area and were the same length.

Metal sampleResistance at 0°C

in ohmsResistance at 100°C in

ohms

P 4.05 5.67

Q 2.65 3.48

R 6.0 9.17

S 1.70 2.23

A graph of the results for one of the metal samples is shown.

Temperature in °C

(i) Which metal sample, P, Q, R or S, has the data shown in the graph?

(1)

(ii) One of the results is anomalous. Circle this result on the graph.

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(iii) Suggest a reason for the anomalous result.

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(1)

(iv) The same equipment used in the investigation could be used as a thermometerknown as a ‘resistance thermometer.’

Suggest two disadvantages of using this equipment as a thermometer compared to aliquid-in-glass thermometer.

1. ____________________________________________________________

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2. ____________________________________________________________

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(2)

(Total 14 marks)

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(a) The diagram shows the circuit used to obtain the data needed to plot the current–potentialdifference graph for a filament bulb.

(i) Why is the component labelled ‘ J’ included in the circuit?

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(1)

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(ii) The resistance of the bulb increases as the potential difference across the bulbincreases. Why?

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(1)

(iii) The bulb is at full brightness when the potential difference across the bulb is 12 V.The current through the bulb is then 3 A.

Calculate the power of the bulb when it is at full brightness and give the unit.

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Power = _________________________

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(b) In this question you will be assessed on using good English, organising information clearlyand using specialist terms where appropriate.

The table gives data about two types of light bulb people may use in their homes.

Type of light bulbEnergy

efficiencyCost of onelight bulb

Average lifetimein hours

Halogen 10% £1.95 2 000

Light Emitting Diode(LED)

32% £11.70 36 000

Both types of light bulb produce the same amount of light.

Evaluate, in terms of cost and energy efficiency, the use of the two types of light bulb.

To gain full marks you must compare both types of light bulb and conclude which light bulbwould be the best to use.

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(6)

(Total 11 marks)

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The picture shows a washing machine. When the door is closed and the machine switched on,an electric motor rotates the drum and washing.

(a) Complete the following sentences.

(i) An electric motor is designed to transform electrical energy into

________________________ energy.

(1)

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(ii) Some of the electrical energy supplied to the motor is wasted as

_______________________ energy and _______________________ energy.

(1)

(b) What happens to the energy wasted by the electric motor?

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(1)

(c) The graph shows that washing clothes at a lower temperature uses less energy thanwashing them at a higher temperature. Using less energy will save money.

Temperature setting in °C

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(i) Electricity costs 15p per kilowatt-hour (kWh).

The temperature setting is turned down from 40 °C to 30 °C.

Use the graph and equation in the box to calculate the money saved each washcycle.

total cost = number of kilowatt-hours x cost per kilowatt-hour

Show clearly how you work out your answer.

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Money saved = ________________________

(2)

(ii) Reducing the amount of energy used by washing machines could reduce the amountof carbon dioxide emitted into the atmosphere.

Explain why.

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(2)

(Total 7 marks)

(a) The diagram shows the circuit used to investigate the resistance of a sample of a material.The diagram is not complete; the ammeter and voltmeter are missing.

(i) Draw the symbols for the ammeter and voltmeter on the diagram in the correctplaces.

(2)

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(ii) How can the current through the material be changed?

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(1)

(b) The material, called conducting putty, is rolled into cylinders of different lengths but withequal thickness.

Graph 1 shows how the resistance changes with length.

Length in centimetres

(i) The current through a 25 cm length of conducting putty was 0.15 A.

Use Graph 1 to find the resistance of a 25 cm length of conducting putty.

Resistance = _________________________ ohms

(1)

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(ii) Use your answer to (b) (i) to calculate the potential difference across a 25 cm lengthof conducting putty.


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Potential difference = _________________________ volts

(2)

(c) A second set of data was obtained using thicker pieces of conducting putty. Both sets ofresults are shown in Graph 2.

Length in centimetres

(i) What is the relationship between the resistance and the thickness of the conductingputty?

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(1)

(ii) Name one error that may have reduced the accuracy of the results.

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(1)

(Total 8 marks)

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Aluminium is produced from an ore called bauxite.

Bauxite contains aluminium oxide.

Look at Figure 1.

Figure 1

(a) Calculate the percentage of bauxite that is converted into aluminium oxide.

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Percentage = _________________

(2)

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(b) Show by calculation that the mass of aluminium produced is less than that expected from 1950 kg aluminium oxide (Al2O3).

You should state the difference in the mass of aluminium expected and the mass ofaluminium produced to three significant figures.

Relative atomic masses (Ar): O = 16; Al = 27

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(c) Figure 2 shows an electrolysis cell used to extract aluminium.

Figure 2

Why does the carbon anode used in the electrolysis cell need to be continually replaced?

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(3)

(d) In an electrolysis cell the current is 1.5 × 105 A, at a potential difference of 4V.

Calculate the energy transferred by the electrolysis cell in 24 hours.

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Energy transferred = _________________ J

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(e) The half equation at the cathode is:

Al3+ + 3 e– Al

Calculate the number of moles of electrons needed to produce 1 000 kg of aluminium.

Give your answer to three significant figures.

Relative atomic mass (Ar): Al = 27

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Answer = _________________ moles

(3)

(Total 16 marks)

A student is investigating some electrical components.

(a) Describe how the student could set up a circuit to find the resistance of a lamp.

You should include a circuit diagram in your answer.

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(b) The student is given an electrical component in a sealed box.

She has to find out what the electrical component is by experiment.

The student records the current and the potential difference for the component.

Her results are shown in the figure below.

Explain how the student could know that the electrical component in the sealed box is notan ohmic conductor.

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(c) What is the electrical component in the sealed box?


Component _______________________________________________________

Explanation _______________________________________________________

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(3)

(d) Use the graph to determine the resistance of the component at 2.3 V.

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Resistance = __________________ Ω(4)

(Total 13 marks)

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Table 1 shows information about different light bulbs.

The bulbs all have the same brightness.

Table 1

Type of bulbInput power in

wattsEfficiency

Halogen 40 0.15

Compactfluorescent (CFL)

14 0.42

LED 7 0.85

(a) (i) Calculate the useful power output of the CFL bulb.

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Useful power output = _______________ watts

(2)

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(ii) Use your answer to part (i) to calculate the waste energy produced each second by aCFL bulb.

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Waste energy per second = _______________ joules

(1)

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(b) (i) A growth cabinet is used to investigate the effect of light on the rate of growth ofplants.

The figure below shows a growth cabinet.

In the cabinet the factors that affect growth can be controlled.

A cooler unit is used to keep the temperature in the cabinet constant. The cooler unitis programmed to operate when the temperature rises above 20 °C.

The growth cabinet is lit using 50 halogen bulbs.

Changing from using halogen bulbs to LED bulbs would reduce the cost of runningthe growth cabinet.

Explain why.

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(ii) A scientist measured the rate of growth of plants for different intensities of light.

What type of graph should be drawn to present the results?

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Give a reason for your answer.

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(1)

(c) Table 2 gives further information about both a halogen bulb and a LED bulb.

Table 2

Type ofbulb

Cost tobuy

Lifetime inhours

Operating cost over thelifetime of one bulb

Halogen £1.50 2 000 £16.00

LED £30.00 48 000 £67.20

A householder needs to replace a broken halogen light bulb.

Compare the cost efficiency of buying and using halogen bulbs rather than a LED bulb overa time span of 48 000 hours of use.

Your comparison must include calculations.

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(4)

(Total 12 marks)

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(a) Figure 1 shows the apparatus used to obtain the data needed to calculate the resistance ofa thermistor at different temperatures.

Figure 1

Power supply

(i) In the box below, draw the circuit symbol for a thermistor.

(1)

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(ii) Use the data given in Figure 1 to calculate the resistance of the thermistor at 20 °C.

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Resistance = _____________ ohms

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(iii) Figure 2 shows the axes for a sketch graph.

Complete Figure 2 to show how the resistance of the thermistor will change as thetemperature of the thermistor increases from 20 °C to 100 °C.

Figure 2

Temperature in °C

(1)

(iv) Which one of the following is most likely to include a thermistor?

Tick () one box.

An automatic circuit to switch a plant watering system on and off.

An automatic circuit to switch an outside light on when it gets dark.

An automatic circuit to switch a heating system on and off.

(1)

(b) The ammeter used in the circuit has a very low resistance.

Why is it important that ammeters have a very low resistance?

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(c) The table below gives the temperature of boiling water using three different temperaturescales.

Temperature Scale

100 Celsius (°C)

212 Fahrenheit (°F)

80 Réaumur (°Re)

Scientists in different countries use the same temperature scale to measure temperature.

Suggest one advantage of doing this.

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(1)

(d) A student plans to investigate how the resistance of a light-dependent resistor (LDR)changes with light intensity.

The student starts with the apparatus shown in Figure 2 but makes three changes to theapparatus.

One of the changes the student makes is to replace the thermistor with an LDR.

Describe what other changes the student should make to the apparatus.

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(2)

(Total 9 marks)

Solar panels are often seen on the roofs of houses.

(a) Describe the action and purpose of a solar panel.

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(b) Photovoltaic cells transfer light energy to electrical energy.

In the UK, some householders have fitted modules containing photovoltaic cells on theroofs of their houses.

Four modules are shown in the diagram.

The electricity company pays the householder for the energy transferred.

The maximum power available from the photovoltaic cells shown in the diagram is 1.4 ×103 W.

How long, in minutes, does it take to transfer 168 kJ of energy?

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___________________________ Time = ____________________ minutes

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(c) When the modules are fitted on a roof, the householder gets an extra electricity meter tomeasure the amount of energy transferred by the photovoltaic cells.

(i) The diagram shows two readings of this electricity meter taken three months apart.The readings are in kilowatt-hours (kWh).

21 November 0 0 0 4 4

21 February 0 0 1 9 4

Calculate the energy transferred by the photovoltaic cells during this time period.

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Energy transferred = ____________________ kWh

(1)

(ii) The electricity company pays 40p for each kWh of energy transferred.

Calculate the money the electricity company would pay the householder.

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Money paid = ____________________

(2)

(iii) The cost of the four modules is £6000.

Calculate the payback time in years for the modules.

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Payback time = ____________________ years

(3)

(iv) State an assumption you have made in your calculation in part (iii).

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(d) In the northern hemisphere, the modules should always face south for the maximumtransfer of energy.

State one other factor that would affect the amount of energy transferred during daylighthours.

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(1)

(Total 13 marks)

The picture shows an electric cooker hob. The simplified circuit diagram shows how the fourheating elements connect to the mains electricity supply. The heating elements are identical.

When all four heating elements are switched on at full power the hob draws a current of 26 Afrom the 230 V mains electricity supply.

(a) Calculate the resistance of one heating element when the hob is switched on at full power.

Give your answer to 2 significant figures.

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Resistance = _______________ Ω(3)

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(b) The table gives the maximum current that can safely pass through copper wires of differentcross-sectional area.

Cross-sectionalarea in mm2

Maximum safecurrent in amps

1.0 11.5

2.5 20.0

4.0 27.0

6.0 34.0

The power sockets in a home are wired to the mains electricity supply using cablescontaining 2.5 mm2 copper wires. Most electrical appliances are connected to the mainselectricity supply by plugging them into a standard power socket.

It would not be safe to connect the electric cooker hob to the mains electricity supply byplugging it into a standard power socket.

Why?

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(2)

(c) Mains electricity is an alternating current supply. Batteries supply a direct current.

What is the difference between an alternating current and a direct current?

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(2)

(Total 7 marks)

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(a) A student set up the circuit shown in the diagram. The student uses the circuit to obtain thedata needed to plot a current - potential difference graph for a diode.

(i) Draw, in the boxes, the circuit symbol for a diode and the circuit symbol for a variableresistor.

Diode Variable resistor

(2)

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(ii) The student made two mistakes when setting up the circuit.

What two mistakes did the student make?

1. ____________________________________________________________

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2. ____________________________________________________________

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(b) After correcting the circuit, the student obtained a set of data and plotted the graph below.

Potential difference in volts

(i) At what potential difference did the diode start to conduct an electric current?

___________________________________ V

(1)

(ii) Use data from the graph to calculate the resistance of the diode when the potentialdifference across the diode is 0.3 V.

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Resistance = _____________ ohms

(3)

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(c) The diagram shows the trace produced by an alternating current (a.c.) supply on anoscilloscope.

Each horizontal division on the oscilloscope screen represents a time of 0.01s.

(i) Calculate the frequency of the a.c. supply.

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Frequency = _______________________ hertz

(2)

(ii) A diode is now connected in series with the a.c. power supply.

Why does the diode cause the trace on the oscilloscope screen to change?

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(2)

(Total 12 marks)

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(a) Describe the difference between an alternating current (a.c.) and a direct current (d.c.).

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(b) The diagram shows how the electric supply cable is connected to an electric kettle.The earth wire is connected to the metal case of the kettle.

If a fault makes the metal case live, the earth wire and the fuse inside the plug protectanyone using the kettle from an electric shock.

Explain how.

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(2)

(Total 4 marks)

The table gives data about two types of low energy bulb.

Type of bulb Power inputin watts

Efficiency Lifetimein hours

Cost ofone bulb

Compact FluorescentLamp (CFL)

8 20% 10 000 £3.10

Light Emitting Diode(LED)

5 50 000 £29.85

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(a) Both types of bulb produce the same useful power output.

(i) Calculate the useful power output of the CFL.


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Useful power output = _________________________ W

(2)

(ii) Calculate the efficiency of the LED bulb.


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Efficiency = ___________________________

(1)

(b) LED bulbs are expensive. This is because of the large number of individual electronic LEDchips needed to produce sufficient light from each bulb.

(i) Use the data in the table to evaluate the cost-effectiveness of an LED bulb comparedto a CFL.

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(2)

(ii) Scientists are developing brighter and more efficient LED chips than those currentlyused in LED bulbs.

Suggest one benefit of developing brighter and more efficient LED chips.

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(1)

(Total 6 marks)

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(a) The resistance of a 24 W, 12 V filament lamp depends on the current flowing through thelamp. For currents up to 0.8 A, the resistance has a constant value of 2.5 Ω.

(i) Use the equation in the box to calculate the potential difference across the lamp whena current of 0.8 A flows through the lamp.

potential difference = current × resistance


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Potential difference = ______________________________ V

(2)

20

(ii) When the potential difference across the lamp is 12 V, the current through the lamp is2 A.

On the axes below, draw a current–potential difference graph for the filament lampover the range of potential difference from 0 to 12 volts.

(2)

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(iii) Why does the resistance of the lamp change when the current through the lampexceeds 0.8 A?

______________________________________________________________

______________________________________________________________

(1)

(b) The lamp is now included in a circuit. The circuit is switched on for 2 minutes. During thistime, 72 coulombs of charge pass through the lamp.

Use the equation in the box to calculate the energy transformed by the lamp while thecircuit is switched on.

energy transformed = potential difference × charge


___________________________________________________________________

___________________________________________________________________

Energy transformed = ______________________________ J

(2)

(Total 7 marks)

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Mark schemes

(a) 0.093 A11

(b) 0.093 A1

(c) (increasing the resistance) decreases the current1

therefore (the lamp will be) dimmer1

(d) potential difference = current × resistance

accept correct rearrangement with R as subject1

(e) 3.3 = 0.15 × R1

R = 3.3 / 0.15 (Ω)1

R = 22 (Ω)1

allow 22 (Ω) without working shown for 3 marks

(f) line drawn from the origin with a decreasing gradient.1

[9]

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(a) electrons1

(b)

extra lines from a symbol negate the mark3

(c) the total power = 7360 watts1

current = 7360 ÷ 2301

= 32 A

allow 32 with no working shown for 3 marks1

so the current is greater than 30 A1

2

(d) to increase the voltage (across the cables) or to decrease the current (through the cables)1

reducing energy losses (in the cables)

do not allow electricity for energy

do not allow no energy loss1

increasing the efficiency of transmission1

(e) to decrease the potential difference for domestic use1

(f)

1

(g) 405 / 9001

=0.45

accept 45%1

allow 0.45 or 45% with no working shown for 2 marks

[15]

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(a)

battery connected correct way round1

3

ammeter and voltmeter correct way round1

(b) 6.4 V1

(c) (the lamp will) get dimmer1

because increasing the resistance decreases the current1

(d) potential difference = current × resistance

allow V = IR1

(e) 3.3 = 0.15 × R1

R = 3.3 ÷ 0.151

= 22(Ω)1

allow 22 with no working shown for 3 marks

[9]

(a) (i) 15014

(ii) transferred to the surroundings by heating

reference to sound negates mark1

(iii) 0.75

450 / 600 gains 1 mark

accept 75% for 2 marks

maximum of 1 mark awarded if a unit is given2

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(iv) 20 (s)

correct answer with or without working gains 2 marks

correct substitution of 600 / 30 gains 1 mark2

(b) (i) to avoid bias1

(ii) use less power and last longer1

1 LED costs £16, 40 filament bulbs cost £80

or

filament costs (5 times) more in energy consumption1

(iii) any one from:

• availability of bulbs• colour output• temperature of bulb surface

1

[10]

(a) advantage

any one from:

• produce no / little greenhouse gases / carbon dioxide

allow produces no / little polluting gases

allow doesn’t contribute to global warming / climate change

allow produce no acid rain / sulphur dioxide

reference to atmospheric pollution is insufficient

produce no harmful gases is insufficient• high(er) energy density in fuel

accept one nuclear power station produces as much power asseveral gas power stations

nuclear power stations can supply a lot of or more energy isinsufficient

• long(er) operating life

allow saves using reserves of fossil fuels or gas1

5

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disadvantage

any one from:

• produce (long term) radioactive waste

accept waste is toxic

accept nuclear for radioactive• accidents at nuclear power stations may have far reaching or long term

consequences• high(er) decommissioning costs

accept high(er) building costs• long(er) start up time

1

(b) (i) 12 000 (kWh)

allow 1 mark for correct substitution eg

2000 × 6

or2 000 000 × 6

or

an answer of 12 000 000 scores 1 mark2

(ii) any idea of unreliability, eg

• wind is unreliable

reference to weather alone is insufficient• shut down if wind too strong / weak• wind is variable

1

(c) any one from:

• cannot be seen• no hazard to (low flying) aircraft / helicopters• unlikely to be or not damaged / affected by (severe) weather

unlikely to be damaged is insufficient• (normally) no / reduced shock hazard

safer is insufficient

less maintenance is insufficient

installed in urban areas is insufficient1

[6]

(a) water moves (from a higher level to a lower level)16

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transferring GPE to KE1

rotating a turbine to turn a generator

accept driving or turning or spinning for rotating

moving is insufficient1

transferring KE to electrical energy

transferring GPE to electrical energy gains 1 mark of the 2 marksavailable for energy transfers

1

(b) (TVs in stand-by) use electricity

accept power / energy1

generating electricity (from fossil fuels) produces CO2

accept greenhouse gas

accept sulfur dioxide1

(CO2) contributes to global warming

accept climate change for global warming

accept greenhouse effect if CO2 given

accept acid rain if linked to sulfur dioxide1

(c) a factor other than scientific is given, eg economic, political or legal

personal choice is insufficient1

[8]

(a) decreases17

(b) a filament bulb

allow bulb1

an LED1

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(c) Marks awarded for this answer will be determined by the Quality of Communication(QoC) as well as the standard of the scientific response.

0 marksNo relevant content.

Level 1 (1−2 marks)There is a basic description of the method. This is incomplete and would not lead toany useful results.

Level 2 (3−4 marks)There is a description of the method which is almost complete with a few minoromissions and would lead to some results.

Level 3 (5−6 marks)There is a detailed description of the method which would lead to valid results.To gain full marks an answer including graph, or another appropriate representationof results, must be given.

examples of the physics points made in the response:

• read V and I• read temperature• apply heat

allow hot water to cool• read V and I at least one other temperature• determine R from V / I• range of temperatures above 50 °C

extra detail:• use thermometer to read temperature at regular intervals of temperature• remove source of heat and stir before taking readings• details of attaining 0 °C or 100 °C• last reading taken while boiling• graph of R against T• at least 3 different temperatures

6

(d) (i) Q1

(ii) (80, 3.18)1

(iii) any one from:

• measurement of V too small• measurement of I too big• incorrect calculation of R• thermometer misread

allow misread meter

ignore any references to an error that is systematic1

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(iv) any two from:

• not portable

allow requires a lot of equipment allow takes time to set up• needs an electrical supply• cannot be read directly

accept it is more difficult to read compared to liquid-in-glass2

[14]

(a) (i) to obtain a range of p.d. values

accept increase / decrease current / p.d. / voltage / resistance

accept to change / control the current / p.d. / voltage / resistance

to provide resistance is insufficient

a variable resistor is insufficient

do not accept electricity for current1

8

(ii) temperature of the bulb increases

accept bulb gets hot(ter)

accept answers correctly

expressed in terms of collisions between (free) electrons and ions /atoms

bulb gets brighter is insufficient1

(iii) 36

allow 1 mark for correct substitution, ie 12 × 3 provided nosubsequent step shown

2

watt(s) / W

accept joules per second / J/s

do not accept w1

(b) Marks awarded for this answer will be determined by the Quality of WrittenCommunication (QWC) as well as the standard of the scientific response. Examinersshould also refer to the information in the Marking guidance, and apply a ‘best-fit’approach to the marking.

0 marksNo relevant content.

Level 1 (1-2 marks)There is a basic comparison of either a cost aspect or an energy efficiency aspect.

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Level 2 (3-4 marks)There is a clear comparison of either the cost aspect or energy efficiency aspectORa basic comparison of both cost and energy efficiency aspects.

Level 3 (5-6 marks)There is a detailed comparison of both the cost aspect and the energy efficiencyaspect.

For full marks the comparisons made should support a conclusion as to which type ofbulb is preferable.

Examples of the points made in the response:

cost

• halogen are cheaper to buy

simply giving cost figures is insufficient

• 6 halogen lamps cost the same as one LED

• LEDs last longer

• need to buy 18 / more halogen lamps to last the same time as one LED

• 18 halogens cost £35.10

• costs more to run a halogen than LED

• LED has lower maintenance cost (where many used, eg large departmentalstore lighting)

energy efficiency

• LED works using a smaller current

• LED wastes less energy

• LEDs are more efficient

• LED is 22% more energy efficient

• LED produces less heat

• LED requires smaller input (power) for same output (power)6

[11]

(a) (i) kinetic

do not accept movement1

9

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(ii) thermal sound

accept heat for thermaldo not accept noise for sound

both answers required in either order1

(b) transferred to surroundings / surrounding molecules / atmosphere

‘it escapes’ is insufficient

orbecomes dissipated / spread out

accept warms the surroundings

accept degraded / diluted

accept a correct description for surroundings eg to the washingmachine

do not accept transformed into heat on its own1

(c) (i) 3 (.0 p)

allow 1 mark for correct substitution of correct values ie 0.2 x 15

allow 1 mark for calculating cost at 40°C (16.5p)

or

cost at 30°C (13.5p)2

(ii) any two from:

• less electricity needed

ignore answers in terms of the washing machine releasing lessenergyan answer in terms of the washing machine releasing CO2 negatesmarkdo not accept less energy is produced

• fewer power stations needed

• less fuel is burned

accept a correctly named fueldo not accept less fuel is needed

2

[7]

(a) (i) ammeter symbol correct and drawn in series

do not accept lower case a1

10

accept

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voltmeter symbol correct and drawn in parallel with the material

1

do not accept

(ii) adjust / use the variable resistor

accept change the resistance

orchange the number of cells

accept battery for cellaccept change the pd / accept change the voltage

accept increase / decrease for change1

(b) (i) 37.5 (Ω)accept answer between 36 and 39 inclusive

1

(ii) 5.6(25) or their (b)(i) × 0.15

allow 1 mark for correct substitution ie 37.5 or their (b)(i) × 0.15provided no subsequent step shown

2

(c) (i) the thicker the putty the lower the resistance

answer must be comparativeaccept the converse

1

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(ii) any one from:

• measuring length incorrectly

accept may be different length

• measuring current incorrectly

do not accept different currents

• measuring voltage incorrectly

do not accept different voltage

• ammeter / voltmeter incorrectly calibrated

• thickness of putty not uniform

do not accept pieces of putty not the same unless qualified

• meter has a zero error

do not accept systematic / random error

accept any sensible source of error eg putty at differenttemperaturesdo not accept human error without an explanationdo not accept amount of putty not same

1

[8]

(a) 1 950 / 2 500 × 100111

78 (%)1

(b) expected mass of aluminium

1950 × 54 / 1021

= 1032.351

mass not collected

1032.35 − 1 000

= 32.4

allow 32.4 with no working shown for 3 marks1

incorrect number of sig. figs max 2 marks

(c) because oxygen is formed at the anode1

which reacts with the carbon anode to produce carbon dioxide1

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and wears it away1

(d) power = 1.5 × 105 × 41

= 6.0 × 105 W1

24 hours = 24 × 60 × 60 = 8.64 × 104 seconds1

energy transferred = 6.0 × 105 × 8.64 × 104

allow ecf from power calculation1

= 5.184 × 1010

allow 5.184 × 1010 with no working for 5 marks1

(e) 3 moles of electrons are needed to produce 27 g or 0.027 kg aluminium1

so moles of electrons to produce 1 000 kg = 1 000 / 0.027 × 31

= 111 000

allow 111 000 with no working shown for 3 marks1

incorrect no. of sig. figs max 2 marks

[16]

(a)

ammeter connected in series1

12

voltmeter connected in parallel1

measure the potential difference across the lamp at known current1

calculate resistance from measured values using V = IR1

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(b) for ohmic conductors the current is directly proportional to the potential difference appliedacross it

1

this graph is curved so it is not an ohmic conductor1

(c) diode1

because it has a high resistance with negative potential differences1

and a low resistance for positive potential differences.1

allow answers in terms of current

(d) tangent to the curve drawn at 2.3 V1

correct reading of Δy and Δx from graph1

either

substitution of values into V = IR (1)1

value of R calculated (1)

accept values in the range 0.50 to 0.651

or

calculation of gradient (1)

allow ecf from incorrect readings of Δy and Δx

calculation of R = 1 / gradient (1)

accept values in the range 0.50 to 0.65

[13]

(a) (i) 5.88 (watts)

an answer of 5.9 scores 2 marks

allow 1 mark for correct substitution ie

0.42 =

allow 1 mark for an answer of 0.0588 or 0.0592

13

(ii) 8.12

allow 14 – their (a)(i) correctly calculated1

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(b) (i) input power / energy would be (much) less (reducing cost of running)

accept the converse

electricity is insufficient1

(also) produce less waste energy / power

accept ‘heat’ for waste energy1

(as the waste energy / power) increases temperature of the cabinet1

so cooler on for less time1

(ii) line graph

need to get both parts correct

accept scattergram or scatter graph

both variables are continuous

allow the data is continuous1

(c) number of bulbs used-halogen=24 (LED=1)1

total cost of LED = £30 + £67.20 = £97.20

accept a comparison of buying costs of halogen £36 and LED £301

total cost of halogen= 24 x £1.50 + 24 x £16.00 = £420orbuying cost of halogen is £36 and operating cost is £384

accept a comparison of operating costs of halogen £384 and LED£67.20

allow for 3 marks the difference in total cost is £322.80 if thenumber 24 has not been credited

1

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statement based on correct calculations that overall LED is cheaper

must be both buying and operating costs

an alternative way of answering is in terms of cost per hour:

buying cost per hour for LED = 0.0625p/£0.000625

buying cost per hour for halogen = = 0.075p/£0.00075

a calculation of both buying costs scores 1 mark

operating cost per hour for LED = = 0.14p/£0.0014

operating cost per hour for halogen= = 0.8p/£0.008

a calculation of both operating costs scores 1 mark

all calculations show a correct unit

all units correct scores 1 mark

statement based on correct calculations of both buying and operating costs, thatoverall LED is cheaper

correct statement scores 1 mark1

[12]

(a) (i)

1

14

(ii) 360

allow 1 mark for correct substitution, ie 9 = 0.025 × R2

(iii) sketch graph of correct shape, ie

1

(iv) An automatic circuit to switch a heating system on and off.1

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(b) so ammeter reduces / affects current as little as possible

accept so does not reduce / change the current (it is measuring)

accurate reading is insufficient

not change the resistance is insufficient1

(c) gives a common understanding

accept is easier to share results

accept can compare results

do not need to be converted is insufficient

prevent errors is insufficient1

(d) replace Bunsen (and water) with a lamp

accept any way of changing light level1

replace thermometer with light sensor

accept any way of measuring a change in light level

datalogger alone is insufficient1

[9]

(a) water heated by radiation (from the Sun)

accept IR / energy for radiation1

15

water used to heat buildings / provide hot water

allow for 1 mark heat from the Sun heats water if no other marksgiven

references to photovoltaic cells / electricity scores 0 marks1

(b) 2 (minutes)

1.4 × 103 =

gains 1 mark

calculation of time of 120 (seconds) scores 2 marks3

(c) (i) 150 (kWh)1

(ii) £60(.00) or 6000 (p)

an answer of £6000 gains 1 mark

allow 1 mark for 150 × 0.4(0) 150 × 40

allow ecf from (c)(i)2

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(iii) 25 (years)

an answer of 6000 / 240or6000 / their (c)(ii) × 4gains 2 marks

an answer of 6000 / 60or6000 / their (c)(ii) gains 1 mark, ignore any other multiplier of (c)(ii)

3

(iv) any one from:

• will get £240 per year

accept value consistent with calculated value in (c)(iii)• amount of light is constant throughout the year• price per unit stays the same• condition of cells does not deteriorate

1

(d) any one from:

• angle of tilt of cells• cloud cover• season / shade by trees• amount of dirt

1

[13]

(a) 35

an answer with more than 2 sig figs that rounds to 35 gains 2 marks

an answer 8.8 gains 2 marks

an answer with more than 2 sig figs that rounds to 8.8 gains 1 mark3

16

allow 2 marks for correct method, ie

allow 1 mark for I = 6.5 (A) or R =

(b) (maximum) current exceeds maximum safe current for a 2.5 mm2 wire

accept power exceeds maximum safe power for a 2.5 mm2 wire

or(maximum) current exceeds 20 (A)

(maximum) current = 26 (A) is insufficient1

a 2.5 mm2 wire would overheat / melt

accept socket for wire

do not accept plug for wire1

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(c) a.c. is constantly changing direction

accept a.c. flows in two directions

accept a.c. changes direction

a.c. travels in different directions is insufficient1

d.c. flows in one direction only1

[7]

(a) (i) symbol for a diode

accept 1

17

1

symbol for a variable resistor

(ii) voltmeter is in series or voltmeter is not in parallel1

ammeter is in parallel or ammeter is not in series

accept an answer in terms of how the circuit should be corrected

voltmeter and ammeter are wrong way around is insufficient1

(b) (i) 0.2 (V)

accept any value between 0.20 and 0.21 inclusive1

(ii) 37.5

allow 1 mark for I = 0.008orallow 2 marks for correct substitution, ie 0.3 = 0.008 × Rorallow 1 mark for a correct substitution using I = 0.8 or I = 0.08or I = 0.009orallow 2 marks for answers of 0.375 or 3.75 or 33(.3)

3

(c) (i) 25

allow 1 mark for obtaining period = 0.04(s)2

(ii) diode has large resistance in reverse / one direction1

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so stops current flow in that / one direction

allow diodes only let current flow one way / direction

allow 1 mark for the diode has half-rectified the (a.c. power) supply1

[12]

(a) d.c. flows in (only) one direction118

a.c. changes direction (twice every cycle)

accept a.c. constantly changing direction

ignore references to frequency1

(b) a current flows through from the live wire / metal case to the earth wire

accept a current flows from live to earth

do not accept on its own if the current is too high1

this current causes the fuse to melt

accept blow for melt

do not accept break / snap / blow up for melt1

[4]

(a) (i)

1.6 (W)

allow 1 mark for correct substitution ie

2

19

(ii)

32 (%) / 0.32ortheir (a)(i) ÷ 5 correctly calculated

ignore any units1

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(b) (i) any two from:

• comparison over same period of time of relative numbers of bulbsrequired eg over 50 000 hours 5 CFL’s required to 1 LED

accept an LED lasts 5 times longer

• link number of bulbs to cost eg 5 CFL’s cheaper than 1 LED

an answer in terms of over a period of 50 000 hours CFLs cost£15.50 (to buy), LED costs £29.85 (to buy) so CFLs are cheaperscores both marks

an answer in terms of the cost per hour (of lifetime) being cheaperfor CFL scores 1 mark if then correctly calculated scores bothmarks

• over the same period of time LEDs cost less to operate (than CFLs)2

(ii) any one from:

• price of LED bulbs will drop

do not accept they become cheaper

• less electricity needs to be generated

accept we will use less electricity

• less CO 2 produced

• fewer chips needed (for each LED bulb)

• fewer bulbs required (for same brightness / light)

• less energy wasted

do not accept electricity for energy1

[6]

(a) (i) 2

allow 1 mark for correct substitution i.e. 0.8 × 2.5 provided nofurther step shown

2

20

(ii) straight line drawn from origin to 2, 0.8ortheir (a)(i), 0.8

1

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curve from 2, 0.8 to 12,2ortheir (a)(i) 0.8 to 12,2

accept curve from 2, 0.9 to 12,2

or

their (a)(i) 0.9 to 12,2

‘convex’ curve required

accept a curve that flattens between 10 and 12V1

(iii) filament / lamp gets hot

accept temperature increases1

(b) 108

allow 1 mark for correct substitution i.e. 1.5 × 72 provided no furtherstep shown

2

[7]

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name: p2 electricity - immanuel college, bradforda student plugs all four of the appliances into one...

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