1

Surname

Name

American Academy Larnaca

Year 4 Physics

Semester 2

Test

Unit P1 Universal Physics

P1.26 Generating electricity

Unit P2 Physics for your future

Topic 1 Static and current electricity

Topic 2 Controlling and using electric currents

Part A

Time: 20 minutes

1

FORMULAE

You may find theses formulae useful

charge = current × time Q = I × t

potential difference = current × resistance V = I × R

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

energy transferred = current × potential difference × time E = I × V × t

speed = distance

time v =

s

t

acceleration = change in velocity

time taken a =

v - u

t

force = mass × acceleration F = m × a

weight = mass × gravitational field strength W = m × g

momentum = mass × velocity p = m × v

force = change in momentum

time F =

(mv - mu)

t

work done = force × distance moved in the direction of the force E = F × d

power = work done

time taken P =

E

t

gravitational potential energy = mass × gravitational field strength × vertical height GPE = m × g × h

kinetic energy = 1

2 × mass × (velocity)

2 KE =

1

2 × m × v2

Do not forget to include units in all your answers.

1. The graph shows how the electric current through a 12 V filament bulb varies with the potential difference across the bulb.

(a) What is the meaning of the following terms?

electric current (1) .............................................................................................................................................. .............................................................................................................................................. potential difference (1) .............................................................................................................................................. ..............................................................................................................................................

(b) The resistance of the metal filament inside the bulb increases as the potential difference across the bulb increases. Explain why. (3) .............................................................................................................................................. .............................................................................................................................................. ..............................................................................................................................................

(c) Use data from the graph to calculate the power at which the filament bulb transfers energy, when the potential difference across the bulb is 6 V. Show clearly how you work out your answer. (2) .............................................................................................................................................. ..............................................................................................................................................

Power = ................................... W

[Total for Question = 7 marks]

2. Graph 1 shows an alternating current while graph 2 shows a direct current.

The two graphs differ in several ways. State the difference between the currents which makes one alternating and the other direct. (2) ................................................................................................................................................

................................................................................................................................................

A light emitting diode (LED) can only emit light when connected correctly to a potential difference.

Use this information to suggest what happens when this alternating voltage is connected across the LED. You may sketch a graph to explain your answer. (2) ................................................................................................................................................

................................................................................................................................................ ................................................................................................................................................

................................................................................................................................................

[Total for Question = 3 marks]

3. Shock absorbers with springs are used on some motorcycles.

These shock absorbers reduce the bounce on an uneven road. A new shock absorber has been developed to convert some of the movement energy into another form. It consists of magnets which slide inside a coil when the motorcycle goes over a bump.

Some of the energy which would otherwise be wasted can be recovered and so fuel is saved. (i) Explain how this new type of shock absorber can provide electrical energy. (2) ..............................................................................................................................................

..............................................................................................................................................

..............................................................................................................................................

.............................................................................................................................................. (ii) The diagram shows the bumps on the surface of two roads, L and M.

Why the device will transfer more energy on road L than on road M for a motorcycle travelling at the same speed? (2) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. ..............................................................................................................................................

[Total for Question = 5 marks]

4. Waste gases contain smoke particles.

The diagram shows how smoke particles can be removed from waste gases as they rise through a chimney.

When the smoke particles go through the metal grid they become negatively charged. When the negatively charged smoke particles move up the chimney, they are attracted to the metal plates. (i) Explain how the metal plates attract the smoke particles. (3) .

. .

(ii) Explain what happens to the charge on the smoke particles when they reach the metal plate. (2)

.

[Total for Question is 5 marks]

[Total marks for Part B =20]

1

Surname

Name

American Academy Larnaca

Year 4 Physics

Semester 2

Test

Unit P1 Universal Physics

P1.26 Generating electricity

Unit P2 Physics for your future

Topic 1 Static and current electricity

Topic 2 Controlling and using electric currents

Part B

Time: 20 minutes

1

FORMULAE

You may find theses formulae useful

charge = current × time Q = I × t

potential difference = current × resistance V = I × R

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

energy transferred = current × potential difference × time E = I × V × t

speed = distance

time v =

s

t

acceleration = change in velocity

time taken a =

v - u

t

force = mass × acceleration F = m × a

weight = mass × gravitational field strength W = m × g

momentum = mass × velocity p = m × v

force = change in momentum

time F =

(mv - mu)

t

work done = force × distance moved in the direction of the force E = F × d

power = work done

time taken P =

E

t

gravitational potential energy = mass × gravitational field strength × vertical height GPE = m × g × h

kinetic energy = 1

2 × mass × (velocity)

2 KE =

1

2 × m × v2

Do not forget to include units in all your answers.

1. A car battery sends a current through a metal wire.

(a) Complete the sentence by putting a cross ( ) in the box next to your answer. The particles that flow in the metal wire are (1)

A atoms

B electrons

C protons

D neutrons

(b) The current in a wire is 3.7 A. Calculate the charge that flows into the wire in 13 s. (2) !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!. !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.

(c) Plastic is an insulator.

A student rubs a piece of plastic with a cloth. This gives the plastic a negative charge. Explain how the plastic is charged by the rubbing. (2)

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.

!...!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.

(Total for Question is 5 marks)

2. The photograph shows a device used to measure the amount of light.

The circuit diagram shows how the components inside this device are connected.

(i) Complete the sentence by putting a cross ( ) in the box next to your answer. The meter used in this circuit is (1)

A a voltmeter connected in series with the LDR

B a voltmeter connected in parallel with the LDR

C an ammeter connected in series with the LDR

D an ammeter connected in parallel with the LDR

(ii) The amount of light entering the light-dependent resistor (LDR) increases. Which row of the table correctly describes the change in the resistance of the LDR and the change in the current in the circuit?

Put a cross ( ) in the box next to your answer. (1)

resistance of the LDR current in circuit

A increases decreases

B increases increases

C decreases decreases

D decreases increases

(iii) The device is used as a light meter. It has a 9 V battery. Calculate the current when the resistance of the LDR is 600 Ω. (3) !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!...

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!... !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!...

current = ........................................ A (iv) When the light meter has been used for a long time, the meter reading becomes incorrect.

Suggest what has happened. (2) !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!... !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!...

(Total for Question is 7 marks)

3. (a) The diagram shows an electric circuit with two resistors, R and S.

(i) R has a resistance of 11 ohms. Calculate the potential difference across R. (2) !!!!.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.

!!!.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.

(ii) Use information from the diagram to calculate the current in S. (1)

!!!!.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.

(iii) Complete the sentence by putting a cross ( ) in the box next to your answer. A student wants to measure the battery voltage with a voltmeter.

The voltmeter should be placed (1)

A in series with the battery

B in parallel with the battery

C in parallel with the ammeter

D in series with either resistor R or S *(b) A resistor is a circuit component.

Two other circuit components are a light dependent resistor (LDR) and a thermistor. Explain how LDRs and thermistors can be used to control the current in a circuit. (4)

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.

(Total for Question is 8 marks)

[Total marks for Part B =20]

Mark Scheme Part A

Question Number

Answer Acceptable answers

Mark

1.(a) [rate of] flow of charge (1) change in energy/joules per charge/coulomb (1)

flow of electrons change in energy/joules of current or similar (2)

1.(b) Any three: V I (1) temperature (1) ions/atoms have larger vibrations (1) harders for e’s/charges to pass/be pushed thru (1)

(3)

1.(c) P [= IV] = 1.3 x 6 (1) = 7.8 [W] (1)

(2)

2. direct current has only postive values/one direction (1) alternating current can take positive and negative values (1)

a.c. above and below zero /the line a.c. goes one way and then the other

(2)

A suggestion to include any 2 of the following

(LED) turns on and off

as voltage/current changes direction/ from +ve to –ve/ twice each second (1)

(LED) on for (+ve ) part of cycle (1)

(LED) off for (-ve) part of cycle (1)

Flash(es) / flicker(s) (on and off) current changes every 0.25 s /4 times each second Turns on twice each second = 2 marks Only on when voltage/current is +ve gains both marks

(2)

4.(i) • smoke is negative (1) • plates are positive (1) • positive and negative charges attract (1)

(3)

4.(ii) smoke particles lose their charge / e’s / flows onto plates (1) becoming neutral / positive (1)

(2)

3.(i)

3.(ii)

two of following:

2

Part B

Question number

Answer Acceptable answers Mark

1.(a) B (1)

(b) 3.7 x 13 (1) = 48 (C) (1)

48.1 Correct answer with no calculation scores 2 marks

(2)

(c) An explanation linking

electrons (1) and one of

removed by friction (1)

(transferred) to plastic (1)

["positive electrons/ protons moving", seen anywhere in part (i) or (ii) loses this mark] ignore reference to charge before rubbing transferred from cloth

(2)

(c)(ii) opposite to charge on plastic (1) equal to charge on the plastic (1)

charge on cloth is positive same size as charge on plastic electrons transferred from the cloth equal to electrons lost by cloth

(2)

2.(i) C (1)

2.(ii) D (1)

2.(iii) 9 = I × 600 (1) I = 9/600 (1) = 0.015 (A) OR=15 mA (1)

allow substitution and transposition in either order give full marks for correct answer, no working

(3)

2.(iv) An explanation linking the following • battery voltage has decreased (1) • (so) less current (than expected) (1)

(2)

3.(a)(i) 11x 0.4 (1) = 4.4 (V) (1)

Full marks for correct answer with no calculation

(2)

3.(a)(ii) 0.2 (A) (1) (1)

3.(a)(iii) B (1)

3.(b) LDR Two from:

resistance changes with light intensity (1)

bright light , low resistance (1)

no light (dark), high resistance (1)

low resistance gives high current (1) Thermistor Two from:

resistance changes with temperature (1)

negative temperature coefficient (1)

high temperature, low resistance (1)

low temperature, high resistance (1)

low resistance gives high current (1)