· web view(iii) the bulb is at full brightness when the potential difference across the bulb is...

St Thomas More Catholic School

Q1.An electrical circuit is shown in the figure below.

(a) The current in the circuit is direct current.

What is meant by direct current?

Tick one box.

Current that continuously changes direction.

Current that travels directly to the component.

Current that is always in the same direction.

(1) (b) The equation which links current, potential difference and resistance is:

potential difference = current × resistance

Calculate the potential difference across the battery in the circuit in the figure above.

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

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

Potential difference = .......................................... V(3)

(c) The equation which links current, potential difference and power is:

power = current × potential difference

Calculate the power output of the battery in the figure above.

Give your answer to one significant figure.

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

Power = ......................................... W(2)

(Total 6 marks)


M1.(a) current that is always in the same direction1

(b) total resistance = 30 (Ω)1

V = 0.4 × 301

12 (V)1

allow 12 (V) with no working shown for 3 marksan answer of 8 (V) or 4 (V) gains 2 marks only

(c) P = 0.4 × 12 = 4.81

5 (W)1

allow 5 (W) with no working shown for 2 marksallow 4.8 (W) with no working shown for 1 mark

[6]


Q2. The drawing shows three identical cells and two identical lamps joined in a circuit.

(a) Use the correct symbols to draw a circuit diagram for this circuit. (3)

(b) Each of the cells provides a potential difference (voltage) of 1.5 volts. What is the total potential difference (voltage) provided by all three cells?

.................................................................................................................... volts(1)

(c) Complete this sentence by crossing out the two lines in the box that are wrong.

The current through lamp 2 will be the current through lamp 1.(1)

(Total 5 marks)


M2. (a) circuit symbol for a lamp correct

accept

accept any standard of drawing providing circuit would work

1

circuit symbol for a cell correct1

2 lamps drawn in parallel with 3 cellspolarity of cells must be correct (+ to –) but cells may be either way around

1

(b) 4.51

(c) the same asaccept any clear indication of the correct answer

1[5]


Q3.(a) Figure 1 shows the oscilloscope trace an alternating current (a.c.) electricity supply produces.

Figure 1

One vertical division on the oscilloscope screen represents 5 volts.

Calculate the peak potential difference of the electricity supply.

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

Peak potential difference = ................................................. V(1)

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

40 50 60

In the UK, the frequency of the a.c. mains electricity supply is ............ hertz.(1)

(c) Figure 2 shows how two lamps may be connected in series or in parallel to the 230 volt mains electricity supply.

Figure 2

(i) Calculate the potential difference across each lamp when the lamps are connected in series.

The lamps are identical.

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

Potential difference when in series = ..................... V (1)


M3.(a) 201

(b) 501

(c) (i) 1151

(ii) 2301

(iii) if one goes out the other still worksorbrighter

accept power (output) is greatercan be switched on/off independently is insufficient

1


(d) Figure 3 shows the light fitting used to connect a filament light bulb to the mains electricity supply.

Figure 3

The light fitting does not have an earth wire connected.

Explain why the light fitting is safe to use.

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

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

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

.............................................................................................................................(2)


(d) the outside/casing is plasticthere is plastic around the wires is insufficientit is plastic is insufficient

1

and plastic is an insulatoran answer the light fitting is double insulated gains both marks

1


Q4.A student set up the electrical circuit shown in the figure below.

(a) The ammeter displays a reading of 0.10 A.

Calculate the potential difference across the 45 Ω resistor.

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

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

Potential difference = ............................................. V(2)

(b) Calculate the resistance of the resistor labelled R.

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

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

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

Resistance = ............................................. Ω(3)

(c) State what happens to the total resistance of the circuit and the current through the circuit when switch S is closed.

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

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

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

.............................................................................................................................(2)

(Total 7 marks)


M4.(a) V = 0.10 × 451

4.5 (V)1

(b) R = 12 / 0.101

total resistance = 120 (Ω)1

R = 120 – 105 = 15 (Ω)1

(c) (total) resistance decreases1

(so) current increases1

[7]


Q5.Diagram 1 shows a hairdryer.Diagram 2 shows how the heaters and fan of the hairdryer are connected to a 3-pin plug.The hairdryer does not have an earth wire.

(a) What colour is the insulation around the wire connected to the live pin inside the plug?

............................................................(1)

(b) Why does the hairdryer not need an earth wire?

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

........................................................................................................................(1)

(c) All the switches are shown in the OFF position.

(i) Which switch or switches have to be ON to make:

(1) only the fan work; ............................................................................

(2) heater 2 work? ................................................................................(2)

(ii) The heaters can only be switched on when the fan is also switched on.

Explain why.

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

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

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

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

...............................................................................................................(2)


M5. (a) brown1

(b) outside / case is plastic / an insulatoraccept is double insulatedaccept non-conductor for plasticdo not accept it / hairdryer is plastic

1

(c) (i) (1) S1

and no other1

(2) S1 and S3

both required, either order1

(ii) S1 must be ON (for either heater to work)do not accept reference to ‘fan’ switch

1

S1 switches the fan on1


(d) The table shows the current drawn from the 230 volt mains electricity supply when different parts of the hairdryer are switched on.

Current in amps

Fan only 1.0

Fan and heater 1 4.4

Fan and both heaters 6.5

Calculate the maximum power of the hairdryer.

Show clearly how you work out your answer and give the unit.

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

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

Maximum power = ............................................................(3)

(Total 9 marks)


(d) 1495allow 1 mark for correct substitutionie, 6.5 × 230

2

watt(s) or Wan answer of 1.495 kW gains 3 marksalthough the unit is an independent mark for full creditthe unit and numerical value must be consistentaccept joules per second or J/s

1[9]


Q6.(a) A washing machine is connected to the mains electricity supply using a cable and three-pin plug.

Figure 1 shows a three-pin plug.

Figure 1

Name the materials used in the structure of a plug. Give the reason why each material is used.

Pin .......................................................................................................................

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

Outer case ..........................................................................................................

.............................................................................................................................(1)

(b) The three-pin plug contains a fuse. The fuse is connected to one of the wires inside the cable.

(i) Which one of the wires inside the cable is the fuse connected to?

...................................................................................................................(1)

(ii) The fuse is a thin wire inside a closed glass tube. The wire acts as a resistor.

What effect does a current through a wire have on the wire?

...................................................................................................................(1)

(iii) The power of the washing machine varies between 0.7 kW and 2 kW depending on which part of the wash cycle is operating.

Calculate the maximum current drawn from the mains electricity supply by the washing machine.

The mains electricity supply is at a potential difference of 230 V.

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

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

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

Current = .................................................... A(2)


M6.(a) pinmade from brass because it is (hard and) a (good electrical) conductor

accept copper for brassmetal is insufficientheat conductor on its own negates

1

outer caseplastic/rubber because it is a (good electrical) insulator

heat insulator on its own negates1

(b) (i) live1

(ii) makes it hot/warmmelts is insufficient

1

(iii) 8.7accept an answer that rounds to 8.7allow 1 mark for correct substitution ie 2000 = 230 × Ian answer of 0.0087 or 0.009 or 3.0(4) or 5.65 or 5.7 gains 1 mark

2

(c) Figure 2 shows how the mains electricity cable is connected to the washing machine.

The earth wire is connected to the metal case of the washing machine.

Figure 2


If a fault makes the metal case live, the earth wire and fuse inside the plug prevent the mains cable from overheating and causing a fire.

Explain how.

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

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

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

.............................................................................................................................(2)

(d) New research has shown that many people underestimate the hazards of using mains electricity.

It is important that people do understand the hazards of using mains electricity.

Suggest why.

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

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

.............................................................................................................................(1)

(Total 9 marks)


(c) a (large) current goes from the live wire to the earth wireaccept metal case for live wireaccept a current goes from live to earthdo not accept electricity for current

1

(which causes) the fuse to (overheat and) meltaccept blow for meltbreak is insufficientdo not accept snap / blow up for melt

1

(d) reduce chance of an electric shockaccept to reduce the risk of an accidentaccept prevent electric shockaccept prevent electrocutionaccept prevent or reduce the risk of an (electrical) fireaccept an electric shock can kill youaccept it can kill youaccept so you can use it safely

1[9]


Q7.The current in a circuit depends on the potential difference provided by the cells and the total resistance of the circuit.

(a) Figure 1 shows the graph of current against potential difference for a component.

What is the name of the component?

Draw a ring around the correct answer.

diode filament bulb thermistor

(1)

(b) Figure 2 shows a circuit containing a 6 V battery.

Two resistors, X and Y, are connected in parallel.

The current in some parts of the circuit is shown.

(i) What is the potential difference across X?

Potential difference across X = ............................. V(1)

(ii) Calculate the resistance of X.

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

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

Resistance of X = ............................. Ω(2)


M7.(a) filament bulb1

(b) (i) 6 V1

(ii) 3 Ω or their correctly calculatedallow 1 mark for correct substitution ie6 = 2 × Ror their (i) = 2 × R

2


(iii) What is the current in Y?

Current in Y = ............................. A(1)

(iv) Calculate the resistance of Y.

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

Resistance of Y = ............................. Ω(1)

(v) When the temperature of resistor X increases, its resistance increases.

What would happen to the:• potential difference across X

• current in X

• total current in the circuit?

Tick ( ) three boxes.

Decrease Stay the same Increase

Potential difference across X

Current in X

Total current in the circuit

(3)(Total 9 marks)


(iii) 1 A1

(iv) 6 Ω or their (i) / their (iii) correctly calculated1

(v)

Decrease Stay the same Increase

111

[9]


Q8. The current through component X is measured when different voltages are applied across it.

(a) Name the component labelled Y in the circuit.

.............................................................................................................................(1)

(b) What type of meter is Z?

.............................................................................................................................(1)

(c) The table shows the measurements obtained in this experiment.

Voltage in V 0 0.2 0.4 0.6 0.8

Current in mA 0 0 50 100 150

Draw a graph of the measurements.

(2)

(d) Use the shape of the graph to name component X.

.............................................................................................................................(1)


M8. (a) variable resistoraccept rheostat

1

(b) voltmeter1

(c) straight line correct between 0.2 and 0.8if line incorrect, or no line, and correct plots 0.2 to 0.8 award 1 mark

2

(d) diode / rectifier1

[5]


Q9.(a) Figure 1 shows the current−potential difference graph for three wires, A, B and C.

(i) Using Figure 1, how can you tell that the temperature of each wire is constant?

...............................................................................................................(1)

(ii) Which one of the wires, A, B or C, has the greatest resistance?

Write the correct answer in the box.

Give a reason for your answer.

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

...............................................................................................................(2)

(b) A student measured the resistance of four wires.

The table below shows the resistance of, and other data about, each of the four wires, J, K, L and M.

Wire Type ofmetal

Lengthin cm

Diameterin mm

Resistance

in …….

J copper 50 0.17 0.36

K copper 50 0.30 0.12

L copper 100 0.30 0.24

M constantan 100 0.30 7.00

(i) The last column of the table should include the unit of resistance.

What is the unit of resistance?

.........................................................(1)


M9.(a) (i) p.d. is (directly) proportional to currentorgradient / slope is constantorthe lines show constant resistance

accept lines are straight / diagonal1

(ii) Creason only scores if C is chosen

1

for the same p.d. the current is the smallestaccept lowest gradient and the gradient = 1 / R

1

(b) (i) ohmaccept correct symbol Ω accept an answer written in the table if not given in answer space

1


(ii) The resistance of a wire depends on many factors.

Look at the table. Which two wires from J, K, L and M show that the resistance of a wire depends on the length of the wire?

Wire and wire


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

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

...............................................................................................................(2)

(iii) A student looked at the data in the table and wrote this conclusion:

‘The resistance of a wire depends on the type of metal from which the wire is made.’

The student could not be certain that her conclusion is true for all types of metal.

Suggest what extra data is needed for the student to be more certain that the conclusion is correct

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

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

...............................................................................................................(1)

(c) The resistance of a wire can be calculated using the readings from an ammeter and a voltmeter.

(i) Complete Figure 2 by drawing a voltmeter in the correct position in the circuit. Use the correct circuit symbol for a voltmeter.

(1)


(ii) K and Lreason only scores if both K and L are chosen

1

only length variesaccept type of metal and the diameter are the same

1

(iii) measure the resistance of more wires made from different metalsaccept test more (types of) metalsmeasure the resistance of more wires is insufficient they only use two metals is insufficient

1

(c) (i) voltmeter symbol correct and drawn in parallel with the wire

accept voltmeter symbol correct and drawn in parallel with the battery

1

(ii) correct symbol drawn


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

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

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

...............................................................................................................(1)

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

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

...............................................................................................................(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.

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

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

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

Power = ..................................................(3)


M10.(a) (i) to obtain a range of p.d. valuesaccept increase / decrease current / p.d. / voltage / resistanceaccept to change / control the current / p.d. / voltage / resistanceto provide resistance is insufficienta variable resistor is insufficientdo not accept electricity for current

1

(ii) temperature of the bulb increasesaccept bulb gets hot(ter)accept answers correctly expressed in terms of collisions between (free) electrons and ions / atomsbulb gets brighter is insufficient

1

(iii) 36allow 1 mark for correct substitution, ie 12 × 3 provided no subsequent step shown

2

watt(s) / Waccept joules per second / J/sdo not accept w

1


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

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

Type of light bulb Energy efficiency

Cost of one light bulb

Average lifetime in

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 bulb would be the best to use.

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

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

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

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

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

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

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

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

........................................................................................................................(6)

(Total 11 marks)


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

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

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 efficiency aspect.

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

Examples of the points made in the response:

cost

• halogen are cheaper to buysimply 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 departmental store 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


Q11. The information plate on a hairdrier is shown.

(a) What is the power rating of the hairdrier?

.............................................................................................................................(1)

(b) (i) Write down the equation which links current, power and voltage.

...................................................................................................................(1)

(ii) Calculate the current in amperes, when the hairdrier is being used. Show clearly how you work out your answer.

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

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

Current = .............................. amperes (2)

(iii) Which one of the following fuses, 3A, 5A or 13A, should you use with this hairdrier?

...................................................................................................................(1)

(c) The hairdrier transfers electrical energy to heat energy and kinetic energy.

Calculate the efficiency of the hairdrier in transferring electrical energy into heat energy.

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

Efficiency = ..............................(2)

(Total 7 marks)


M11. (a) 800 (W)accept 0.8kW but this answer must have the unit

1

(b) (i) power = voltage × currentaccept the equation rearrangedaccept P = VIdo not accept C for currentdo not accept P = VA do not accept power = VAdo not accept

unless subsequent calculation shows understanding1

(ii) 3.5 (A)accept a larger number of d.p. but you must be able to round to 3.5allow 1 mark for

current =

or (I =) 2

(iii) 5 (A)independent of (ii) unless e.c.f from part (b)(ii)

1

(c) 0.95 or 95 (%)allow I mark if useful energy output is given as 760 ignore any incorrect unit

2

[7]


Q12.The diagram shows the circuit set up by a student.

(a) The student uses the circuit to test the following hypothesis:

‘The current through a resistor is directly proportional to the potential difference across the resistor.’

(i) If the hypothesis is correct, what should the student predict will happen to the current through the resistor when the potential difference across the resistor is doubled?

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

...............................................................................................................(1)

(ii) Name the component in the circuit used to change the potential difference across the resistor.

...............................................................................................................(1)

(b) The student used the data obtained to plot the points for a graph of current against potential difference.


M12. (a) (i) also doubleincreases is insufficient

1

(ii) variable resistoraccept rheostat / potentiometer

1


(i) Why has the student plotted the points for a line graph and not drawn a bar chart?

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

...............................................................................................................(1)

(ii) One of the points has been identified by the student as being anomalous.

What is the most likely cause for this anomalous point?

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

...............................................................................................................(1)

(iii) Draw a line of best fit for these points.(1)

(iv) Does the data the student obtained support the hypothesis?


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

...............................................................................................................(1)

(Total 6 marks)


(b) (i) the data / results / variables are continuousaccept data / results / variables are not categoric / discrete

1

(ii) misreading the ammeterdo not accept misreading the meter / resultsdo not accept misreading the ammeter and / or voltmeterreading / human error is insufficient

1

(iii) straight line from the origin drawn passing close / throughpoints at 1 V, 5 V, 6 V and ignoring anomalous point

do not accept line drawn ‘dot-to-dot’1

(iv) yesmark is for the reason

supports predictionor(straight) line passes through the originaccept a mathematical argument, eg when p.d. went from 2 to 4 the current went from 0.3 to 0.6it’s directly proportional is insufficient

1[6]


Q13.(a) Figure 1 shows the apparatus used to obtain the data needed to calculate the resistance of a thermistor at different temperatures.

Figure 1

Power supply

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

(1)

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

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

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

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

Resistance = ......................... ohms(2)

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

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

Figure 2

Temperature in °C(1)


M13.(a) (i)

1

(ii) 360allow 1 mark for correct substitution, ie 9 = 0.025 × R

2

(iii) sketch graph of correct shape, ie

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?

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

........................................................................................................................(1)

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

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.

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

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

........................................................................................................................(1)


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

(b) so ammeter reduces / affects current as little as possibleaccept so does not reduce / change the current (it is measuring)accurate reading is insufficientnot change the resistance is insufficient

1

(c) gives a common understandingaccept is easier to share resultsaccept can compare resultsdo not need to be converted is insufficientprevent errors is insufficient

1


Q14. (a) Describe the difference between an alternating current (a.c.) and a direct current (d.c.).

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

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

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

.............................................................................................................................(2)

(b) The diagram shows the information plate on the bottom of an electric wallpaper steamer.

(i) Calculate the current used by the steamer.

Show clearly how you work out your answer.

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

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

Current .............................. A(2)

(ii) Which one of the following fuses should be used inside the plug of the steamer?

Draw a ring around your answer.

1 A 3 A 5 A 10 A 13 A(1)

(Total 5 marks)


M14. (a) d.c. flows in (only) one direction1

a.c. changes direction (twice every cycle)accept a.c. constantly changing directionignore references to frequencyaccept answers presented as a clear diagrame.g.

ac:

1

(b) (i) 10allow 1 mark for correct transformation and substitution i.e.

an answer 0.01 gains 1 mark2

(ii) 13 Ae.c.f.accept the fuse size that is the next listed value greater than answer (b)(i)

1[5]

Q15.A 12 V filament bulb is connected to a 12 V power supply.


The graph shows how the current changes after the bulb is switched on.

(a) (i) After 0.10 seconds, the bulb works at its normal brightness.

What is the current through the bulb when it is working at normal brightness?

Current = ......................................... A(1)

(ii) The bulb works at normal brightness for 30 seconds before it is switched off.

Calculate the charge that flows through the bulb in the 30 seconds before it is switched off. Give the unit.

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

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

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

Charge = ................................. unit .................................(3)

(iii) Calculate the energy transferred by the 12 V bulb when it is working at normal brightness for 30 seconds.

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

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

Energy transferred = .......................................... J(2)


M15.(a) (i) 1.71

(ii) 51or30 × their (i) correctly calculated

allow 1 mark for correct substitution i.e. 1.7

or their (i)2

coulomb / Cdo not accept c

1

(iii) 612ortheir (ii) × 12 correctly calculatedortheir (i) × 360 correctly calculated

allow 1 mark for correct substitution i.e. E = 12 × 51or 12 × their (ii)or their (i) × 360

2


(b) Between 0.02 seconds and 0.08 seconds, there is an increase in both the resistance and the temperature of the metal filament inside the bulb.

Explain, in terms of the electrons and ions inside the filament, why both the temperature and the resistance increase.

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

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

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

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

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

........................................................................................................................(2)

(Total 8 marks)


(b) ions vibrate fasterorions vibrate with a bigger amplitude

accept atoms for ions throughoutaccept ions gain energyaccept ions vibrate moreions start to vibrate is insufficient

1

electrons collide more (frequently) with the ionsor(drift) velocity of electrons decreases

electrons start to collide is insufficientthere are more collisions is insufficient, unless both electrons and ions are implied

1[8]


Q16. The following specification is taken from the instruction booklet of a combination microwave oven.

AC voltage 240 V 50 Hz

Power required

Microwave 1.5 kW

Dual (Roast/Bake) 2.8 kW

Dual (Grill) 2.5 kW

Convection 1.35 kW

Grill 2.3 kW

Output power

Microwave 850 W

Convection heater 1350 W

Grill heater 1000 W

Microwave frequency 2450 MHz

(a) (i) What is the current when the oven is being used to cook in the dual (roast/bake) mode? Show clearly how you work out your answer.

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

Current = ................................. A(2)

(ii) Calculate the resistance of this combination microwave oven when it is being used in the dual (roast/bake) mode. Show clearly how you work out your answer and give the units.

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

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

Resistance = ................................(3)

(b) What is the percentage efficiency of the oven when it is working in the microwave mode?

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

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

Percentage efficiency = .................................. %(2)


M16. (a) (i) power ÷ voltage = current or2800 ÷ 240 = 11.6 – 11.7 or 12

2 marks for correct answer 1 mark for 2.8 ÷ 2402

(ii) resistance = voltage ÷ current

240 ÷ 11.7(efc here)

1

20.5 or 20.57 or 20.6 or 212 marks for correct answer

1

ohms or Ωdo not credit R

1

(b) 850 ÷ 1500 × 100marks only available for division of power

1

= 56.72 marks for correct answerfor 1 mark accept 5670

1[7]

· web view(iii) the bulb is at full brightness when the potential difference across the bulb is...

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