Electrical circuits

1. A bar magnet is brought near a metal rod.

The magnet is then turned around so that its poles have changed positions. The magnet is again brought near to the metal rod.

In both cases the metal rod is attracted to the magnet.

What could the metal rod be?

A another bar magnet

B a piece of aluminium

C a piece of copper

D a piece of iron

0654/11/M/J/13 Q38

2. The circuit shown is used to determine the resistance of a lamp.

The ammeter reading is 2.0A and the voltmeter reading is 6.0V.

What is the resistance of the lamp?

A 0.33Ω B 3.0Ω C 8.0Ω D 12Ω

0654/11/M/J/13 Q39

3. A rod is rubbed with a dry piece of cloth. A scientist holds the rod in her hand and brings it close to a negatively charged polythene strip. The strip is suspended by an insulating thread.

As the rod approaches the polythene strip, the strip moves towards the rod.

Which statement is correct?

A The rod is a negatively charged electrical conductor.

B The rod is a negatively charged electrical insulator.

C The rod is a positively charged electrical conductor.

D The rod is a positively charged electrical insulator.

0654/12/M/J/13 Q38

4. In the circuit, component X is used to control the brightness of the lamp.

What is component X?

A an ammeter

B a fixed resistor

C a fuse

D a variable resistor

0654/12/M/J/13 Q39

5. The circuit shows a current I in a resistor of resistance R.

Which row gives possible values of I and of R?

0654/11/O/N/13 Q38

6. Which diagram shows the magnetic field pattern around a straight wire carrying a current?

0654/13/O/N/13 Q39

7. Which row shows how lamps are connected in a domestic lighting circuit, and gives an advantage of connecting them in this way?

how lamps are connected advantage of connecting them in this way

A in parallel they can be switched separately

B in parallel they share the voltage

C in series they can be switched separately

D in series they share the voltage0654/13/O/N/13 q39

8. The instructions for a household lamp state that the plug should be fitted with a 3A fuse.

What could happen if, by mistake, a 13A fuse is fitted?

A The fuse might melt too easily.

B The lamp might explode if a fault develops.

C The wires connecting the lamp to the plug might overheat if a fault developed.

D Too much voltage might be supplied to the lamp.

0654/11/M/J/12 Q37

9. A 3.0Ωresistor and a 6.0Ωresistor are connected to a power supply as shown.

What is the total resistance of the circuit?

A 2.0Ω B 3.0Ω C 9.0Ω D 18Ω

0654/11/M/J/12 Q38

10. In the lighting circuit in a house, how are lamps usually connected, and what is one reason for this?

usual connection reason

A parallel to allow every lamp to have the full supply voltage

B parallel to share out the voltage equally between the lamps

C series to allow every lamp to have the full supply voltage

D series to share out the voltage equally between the lamps0654/11/M/J/12 Q39

11. The circuit contains four ammeters, P, Q, R and S.

Which statement about the readings on the ammeters is correct?

A The reading on S is less than the reading on P.

B The reading on Q is greater than the reading on S.

C The reading on R is less than the reading on S.

D The reading on Q is greater than the reading on P.

0654/11/O/N/12 Q37

12. A student wishes to measure an e.m.f. and a potential difference.

Which meter(s) does she need?

A an ammeter only

B a voltmeter only

C a voltmeter and an ammeter

D a voltmeter and a newton meter

0654/11/O/N/12 Q38

13. Two resistors, R1 and R2, are connected in parallel as shown.

The combined resistance of R1 and R2 is RT.

Which row is correct?

0654/13/O/N/12 Q37

14. The store has a fire alarm, which detects an increase in temperature.

The fire alarm circuit has a resistor R, a thermistor and a buzzer connected to the battery shown in Fig. 6.2.

Fig. 6.2

Explain what happens to the current in the fire alarm circuit when the temperature increases.

resistance of thermistor goes down ;

current goes up ;

reference to V = IR ;

(supply) voltage is constant ; [max 3]

[3]

0654/31/M/J/13 Q6 part

15. A resistor of 1200Ωis connected in parallel with another resistor of 2400Ω.

Calculate the combined resistance of these two resistors.

State the formula that you use and show your working.

formula

working

[3]

0654/32/M/J/13 Q7

16. Fig. 1.4 shows a small photovoltaic cell (solar cell) being investigated.

(i) A voltmeter is added to the circuit to measure the voltage across the photovoltaic cell.

Using the correct symbol, draw the voltmeter in the correct position on Fig. 1.4.

[1]

(ii) The voltmeter reading is 2.5V when the ammeter reading is 0.2A.

Calculate the power output of the photovoltaic cell.

State the formula that you use and show your working.

formula power = voltage × current ;

working

= 2.5 × 0.2 = 0.5W ;

[2]

0654/33/M/J/13 Q1c

voltmeter in parallel with photocell and correct symbol ;

17. Fig. 8.1 shows a circuit which could be used for the lights on a car. When each headlight bulb is fully lit, 6A passes through it. When each sidelight is fully lit, 0.5A passes through it.

Calculate the total current flowing from the battery when switch A is closed and switch B is open,

2.0 A

switches A and B are both closed.

14 A ; (both required for the mark)

[1]

(b) Fig. 8.2 is a graph showing how the resistance of a thermistor changes with temperature.

Calculate the current that passes through the thermistor at 30°C when it is connected to a 12V power supply.

State the formula that you use, show your working and state the unit of your answer.

Formula V = I ×R ;

working

1300 (ohms) ;

12/1300 = 0.009A ;

unit [3]

0654/31/O/N/13 Q8

18. Fig. 5.1 shows a bicycle with a front light A and a rear light B powered by the same battery.

Fig. 5.2 shows how the lights are connected.

(a) The resistance of light A is 10Ωand the resistance of light B is 5Ω.

Calculate the combined resistance of the two lights in this circuit.

State the formula that you use and show your working.

formula 1/R = 1/R1+ 1/R2/(R) = R1 × R2/R1+R2;

working

correct substitution ;

R = 10/3 = 3.3 Ω;

Ω [3]

(b) The voltage supplied by the battery is 9V.

Calculate the current passing through light A.

State any formula that you use, show your working and state the unit of your answer.

Formula I= V/R ;

working

9/10 = 0.9 A ;

unit [2]

0654/32/O/N/13 Q5

19. Fig. 3.1 shows a circuit used to measure the current passing through a resistor when the voltage across it is changed.

Complete the sentences below using suitable words.

When the voltage across the resistor is reduced, the current through the resistor

__________________________________________________________________________________

When the voltage of the supply is reduced, the voltage across the resistor

_________ decreases and decreases ; _______________________

[1]

(b) The resistance of a piece of wire depends on a number of variables such as the temperature of the wire and the material from which it is made.

State two other factors which affect the resistance of a piece of wire.

1 length ;

2 diameter/cross-sectional area/thickness/width ;

[2]

(c) Fig. 3.2 shows a circuit used to power a small motor.

The voltage across the motor is 3V. The current through the motor is 0.6A.

(i) Calculate the power input to the motor.

State the formula that you use, show your working and state the unit of your answer.

formula (power =) voltage ×current ;

working

= 3 ×0.6 = 1.8W ;

unit [2]

(ii) The motor is able to lift a load of 40N through 1.2m in 36 seconds.

Calculate the power output of the motor.

State the formula that you use, showyour working and state the unit of your

answer. work = force ×distance and (power =) work/time or(P=)Fx/t ;

formula

working

= 40 ×1.2/36 ;

1.3(3)W ;

unit [3]

(iii) Explain why there is a difference between your answers to (i) and (ii).

energy lost/wasted (as heat/sound) ;

[1]

(iv) Calculate the efficiency of the motor.

Show your working.

efficiency = 1.33/1.8 ×100 ;

73.88%(allow 0.74or0.72);

[2]

0654/33/O/N/13 Q3

20.

(a) A student investigates how the change in potential difference across a lamp affects the current flowing through it.

(i) Draw the circuit diagram that the student uses.

ammeter in series ;

voltmeter in parallel ;

means of varying p.d. ;

[max 2 if not a usable circuit]

(ii) During his investigations the student measures the voltage across the lamp as 3.0V and the current passing through the lamp as 0.3A.

Calculate the resistance of the lamp.

State the formula that you use and show your working.

formula used (R =) V/I;

working

= 3/0.3 = 10 Ω;

[2]

(b) This table shows some information about six pieces of wire, all at room temperature (20°C).

wire metal composition length/cm cross-sectional area/mm2

A Copper 10 0.5B Nichrome 10 0.5C Copper 20 0.5D Nichrome 20 0.5E Copper 10 1.0F Copper 20 1.0

(i) Which wire, B or D, will have the greater resistance?

Explain your answer.

wire _____

__________D because it is longer/resistance proportional to length ______________

__________________________________________________________________________________

[1]

(ii) Which wire, A or E, will have the greater resistance?

Explain your answer.

wire ____

A because it has a small cross-section area/it is thinner/resistance inversely proportional to cross-section area ; _______

[1]

(iii) If the resistance of wire A is 10Ω, state the resistance of wires C and E.

wire C resistance =

wire E resistance =

Explain your answers.

C– 20 Ω and twice as long ;

E– 5 Ω and double cross-section area ;

[2]

0654/31/M/J/12Q10

21.

(b) Car brake lights (stop lights) light up when the driver presses on the footbrake pedal. The pedal acts as a switch.

Draw a circuit diagram including a battery to show how this works. Design your circuit so that if one brake light fails, the other still lights up.

[2]

0654/33/M/J/12 Q4

22.

(a) Complete Table 1.1 by choosing one of the words from the list to match each statement.

ammeter ampere circuit coulomb electron

ohm relay volt voltmeter watt

Table 1.1

statement word

a complete loop of conductors circuit

the unit of electrical charge coulomb

an instrument that measures potential difference voltmeter

a device used in switching on circuits Relay 1 mark for any 2

[2]

(b) Fig. 1.1 shows two circuits A and B. All the lamps and both cells are the same.

(i) One lamp is unscrewed from circuit A.

State what happens to the other lamp.

Explain your answer.

goes out (no mark) ;

incomplete circuit ;

[1]

(ii) Explain why lights in a house are connected in parallel and not in series.

so that they can be individually turned on and off ; so that they all get the full mains voltage ; so that if one fails the rest still operate ;

[2]

(iii) The resistance of each lamp is 1.2Ω.

Calculate the combined resistance of the two lamps in circuit B.

State the formula that you use and show your working.

formula used

working

1/R = 1/R1+ 1/R2;

= 1/1.2 + 1/1.2 ;

R = 0.6Ω;

[3]

0654/31/O/N/12 Q1

23.

(a) Electrical devices can develop faults and give a user an electric shock.

Explain how a circuit breaker can stop someone who is using a faulty electrical device from receiving an electric shock. You may draw a diagram if it helps your answer.

circuit breaker operates when current in circuit exceeds certain limit ;

explanation of how it works eg. RCCB or varying strength of electromagnet ;

further explanation of how it works ;

stops the current/flow of electricity in the circuit ; __________________________________________________________________________________

[3]

(b) Some torches (flashlights) use a filament lamp. Fig. 12.1 shows a circuit for measuring the current through a filament lamp as the potential difference is changed.

Fig. 12.2 shows a graph of the results from an experiment using this circuit.

(i) Use the graph to calculate the resistance of the lamp when the potential difference was 2.0V and when the potential difference was 4.0V.

State the formula that you use and show your working.

formula used

working

R = V/I;

= 2/0.2 = 10 Ω and= 4/0.31 = 12.9 Ω;

[2]

(ii) Describe how the current through the filament lamp changes as the voltage increases above 2.0V.

current not (directly) proportional/current does not increase as much ; __________________________________________________________________________________

[1]

(iii) Use your answer to (i) to explain why the current changes in this way.

lamp/filament has got hotter ;

resistance (of lamp/filament) has increased ;

[2]

0654/32/O/N/12 Q12