Part A

Part A 1

Surname

Name

American Academy Larnaca

Year 4 Physics

Semester 2

Test 2

Unit P1

Universal Physics

Topic 5 Electricity

Part A

Time: 20 minutes

FORMULAE

You may find the following formulae useful.

wave speed = frequency × wavelength v = f × λ

takentime

covered distancespeed wave

t

xv

electrical power = current × potential difference P = I × V

cost of electricity = power × time × cost of 1 kilowatt-hour

takentime

usedenergy power

t

EP

%100device) the tosuppliedenergy (total

device) by the nsferredenergy tra (usefulefficiency

Do not forget to include units in all your answers.

Part A

Part A 2

1. The map shows the positions of two towns on either side of a very large coastal bay in

England. The map also shows where a bridge may be built to link the towns. The road

journey from one town to the other is about 60 kilometres at present.

It is estimated that building turbines and generators inside the legs of the bridge would

produce enough electricity for both towns. In addition, enough electricity would be

generated to run electric buses over the bridge between the two towns.

(a) If the bridge is built, what form of renewable energy will be used to generate the

electricity? [1 mark]

…………………………………………………………………………………………………………………

(b) Most people living in the area are in favour of the proposed bridge.

Suggest two reasons why people would be in favour of building the bridge and the

associated electricity generating scheme.

[2 marks] Reason 1: …..…………………………………………………………………………………………………

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Reason 2: …..…………………………………………………………………………………………………

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Even with the proposed bridge, the two towns will need to stay connected to the

National Grid. The diagram shows part of the National Grid.

(c) Give one reason why the towns need to stay connected to the National Grid.

[1 mark] …………………………………………………………………………………………………………………

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Part A

Part A 3

(d) Explain how the step-up transformer increases the efficiency of the National Grid.

[2 marks] …………………………………………………………………………………………………………………

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[Total for Q1 = 6 marks]

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2. A class uses a step-up transformer in a model transmission line.

The transformer is shown below.

The input voltage is 6 V a.c. (alternating current) and there are 20 primary turns.

(a) The output voltage is 24 Va.c. How many secondary turns does the transformer

have? [2 marks] …………………………………………………………………………………………………………………

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Number of turns = …………………………..

(b) A student wants to use an input voltage of 60 Va.c. Why does the teacher tell him

that this is not a good idea? [1 mark]

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[Total for Q2 = 3 marks] _______________________________________________________________________________________

(Turn over)

Part A

Part A 4

3. Coal-fired power stations are used to produce large quantities of electricity. There are

advantages and disadvantages of producing electricity in this way.

(a) State two advantages other than cost.

[2 marks] Advantage 1…………………………………………………………………………………………………

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Advantage 2…………………………………………………………………………………………………

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(b) State two disadvantages other than cost.

[2 marks] Disadvantage 1…………………………………………………………………………………………………

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Disadvantage 2…………………………………………………………………………………………………

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[Total for Q3 = 4 marks]

4. Electrical current is best described as:

A a flow of south poles

B a flow of north poles

C a flow of positive electrons

D a flow of negative electrons

[Total for Q4 = 1 mark]

Part A

Part A 5

5. The diagram shows a generator producing an alternating voltage.

(a) Draw one straight line from each letter to its correct label.

[2 marks]

(b) The generator is connected to a lamp.

The current in the lamp is alternating.

Which of these is an alternating current?

Part A

Part A 6

(c) The generator is turned faster.

Explain why the lamp is brighter now.

[1 mark] …………………………………………………………………………………………………………………

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(d) A larger generator produces a current of 2 A at a voltage of 12 V.

Calculate the electrical power generated.

State the unit.

[2 marks] …………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

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Power=………………….

[Total for Q5 = 6 marks]

TOTAL FOR PART A = 20 MARKS

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END

Part B

Part B 1

Surname

Name

American Academy Larnaca

Year 4 Physics

Semester 2

Test 2

Unit P1

Universal Physics

Topic 5 Electricity

Part B

Time: 20 minutes

FORMULAE

You may find the following formulae useful.

wave speed = frequency × wavelength v = f × λ

takentime

covered distancespeed wave

t

xv

electrical power = current × potential difference P = I × V

cost of electricity = power × time × cost of 1 kilowatt-hour

takentime

usedenergy power

t

EP

%100device) the tosuppliedenergy (total

device) by the nsferredenergy tra (usefulefficiency

Do not forget to include units in all your answers.

Part B

Part B 2

1. The picture shows a new washing machine. When the door is closed and the machine

switched on, an electric motor rotates the drum and washing.

The graph shows that washing clothes at a lower temperature uses less energy than

washing them at a higher temperature. Using less energy will save money.

(a) Electricity costs 12 p 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 wash cycle.

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

Show clearly how you work out your answer. [2 marks]

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Money saved=………………………

(b) Suggest why reducing the amount of energy used by washing machines could reduce

the amount of carbon dioxide emitted into the atmosphere. [1 mark]

…………………………………………………………………………………………………………………

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[Total for Q1 = 3 marks] _______________________________________________________________________________________

Part B

Part B 3

2. The table gives information about some ways of reducing the energy consumption in a

house.

(a) Calculate the payback time for installing “Jacket for hot water tank” [1 mark]

…………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

(b) Show that over 5 years, the most cost-effective method of reducing energy

consumption is to install cavity wall insulation. [2 marks]

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[Total for Q2 = 3 marks]

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(Turn over)

Part B

Part B 4

3. The photograph shows equipment used for generating electricity from renewable sources.

(a) Complete the sentences using words from the box.

The panel of solar cells transforms ..................................................... energy into electrical energy.

The wind turbine transforms ............................................................ energy into electrical energy.

[2 marks]

(b) On a windy day, the wind turbine transfers 78 W of power.

Calculate the amount of energy the turbine transfers in 1 minute.

[2 marks] …………………………………………………………………………………………………………………

…………………………………………………………………………………………………………………

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[Total for Q3 = 4 marks]

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(Turn over)

Part B

Part B 5

4. Complete the sentence by putting a cross in the box next to your answer.

(a) Electrical energy can be measured in

[1 mark]

A amps

B kilowatt-hour

C volts

D watts

Scientists are looking for new ways to produce electricity from renewable resources.

The diagram shows a model of a device to generate electricity from waves.

The coil is fixed to the concrete block.

The magnet can move freely inside the coil.

(b) Explain how this device produces an electric current.

[3 marks] …………………………………………………………………………………………………………………

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(c) Describe how the device can be altered to increase the electric current.

[2 marks] …………………………………………………………………………………………………………………

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[Total for Q4 = 6 marks]

Part B

Part B 6

5*. A windfarm generates electrical power from the wind.

There is a plan to replace the existing transmission line (of 132kV) from the windfarm with

one at the higher potential difference of 400 kV.

The new transmission line will cross more than 200 km of mountains.

The cables will hang 50 m above the ground from 600 new, taller pylons.

Eventually, about 1000 of the old, shorter pylons will be removed.

Discuss the advantages and disadvantages of this plan.

[4 marks] …………………………………………………………………………………………………………………

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[Total for Q5 = 4 marks]

TOTAL FOR PART B = 20 MARKS

END

Mark Scheme

Part A 1. a) tidal [accept wave] b) renewable/cleaner energy cheaper energy cheaper/”greener” transport c) [sufficient] power may not be available in all areas at all times d) higher voltage lower current [for same power] less enery/power loss due to cables heating surroundings

2. a)

N=20 b) output voltage 240V/too high/dangerous 3. a) coal is a concentrated energy source always available huge power b) non-renewable carbon emisions other emissions named, e.g. nitrogen oxide(s), sulphur dioxide 4. D 5. a) P coil Q magnet b) B c) induced voltage/current is higher d) [P=IV=] 2x 12 =24W

Part B 1. a) (1.1-0.9) x 12 = 2.4p b) most electricity generated by burning fossil fuels 2. a) 12/35 = 0.34y ≈ 4 months b) (115 x 5) – 250 = £325 (35 x 5) – 12 = £163 (80 x 5) - 310 = £90 3. a) light kinetic b) [P = Et =] 78 x 60 = 4680J 4. a) B b) waves make ball bob up and down magnet moves up and down in coil inducing a current c) stronger magnet more turns on coil [soft] iron core 5. higher voltage smaller current less power loss/greater efficiency energy savings/reduced [running] costs no fuel costs/ reduced [running] costs no carbon/other emissions [except during manufacture/construction] fewer pylons better aesthetically taller pylons worse aesthetically taller pylons more dangerous for low flying aircraft payback time may be very long