1.
(a) Define potential difference (p.d.).
.........................................................................................................................................................
.................................................................................................................................................... [2]
(b) (i) State the equation which defines electromotive force (e.m.f.) E.
[1]
(ii) The e.m.f. of a battery is 9.0 V. The battery is in a circuit.
Calculate the work done by the battery when it moves a charge of 30 C around a complete
circuit.
work done = ......................................................... [2]
(c) A circuit consists of a d.c. power supply, a lamp and a thermistor.
(i) Draw a circuit diagram of these components connected in series.[2]
(ii) Explain what happens in the circuit you have drawn in (c)(i) when the temperature of the
thermistor is increased.
............................................................................................................................................................
............................................................................................................................................................
……………………………............................................................................................................ [2]
[Total: 9]
2. Fig. 8.1 shows a horizontal, flat coil in a magnetic field
The coil is connected to a cell. The coil rotates.
(a) Determine the direction of movement of the side AB relative to the plane of the coil.
direction of movement = ......................................................... [1]
(b) Explain how you determined the direction in (a).
............................................................................................................................................................
............................................................................................................................................................
...................................................................................................................................................... [2]
(c) State and explain what happens to the coil as it reaches the vertical position.
..........................................................................................................................................................
.........................................................................................................................................................
............................................................................................................................................................
……….................................................................................................................................... [2]
(d) To operate as a motor, a split‑ring commutator and brushes are added to the parts shown in
Fig. 8.1. Explain the effects of the split‑ring commutator and the brushes on the action of the motor.
...................................................................................................................................................
...................................................................................................................................................
............................................................................................................................................. [3]
[Total: 8]
3. Fig. 7.1 shows a circuit that contains a battery, a switch, a voltmeter and three 40 Ω
resistors, R1, R2 and R3.
The switch is open and resistors R1 and R2 form a potential divider.
(a) Describe what is meant by a potential divider.
.........................................................................................................................................................
.........................................................................................................................................................
................................................................................................................................................... [2]
(b) The reading on the voltmeter is 7.5 V.
(i) Calculate the electromotive force (e.m.f.) of the battery.
e.m.f. = ......................................................... [1]
(ii) The switch is closed.
Calculate the resistance of the complete circuit.
resistance = ......................................................... [3]
(c) Calculate the reading on the voltmeter when the switch is closed.
reading = ......................................................... [2]
[Total: 8]
4. The electricity supplied to a town is transmitted using a high-voltage cable.
A transformer in the town has a soft-iron core.
(a) Explain the principle of operation of a simple iron-cored transformer.
................................................................................................................................................................
................................................................................................................................................................
................................................................................................................................................................
................................................................................................................................................................
………………………………………….......................................................................................... [4]
(b) The transformer steps the supply voltage down from 220 000 V to 33 000 V.
(i) There are 450 turns on the secondary coil.
Calculate the number of turns on the primary coil.
number of turns = ......................................................... [2]
(ii) The electrical power transferred to the transformer by the high-voltage cable is 77 MW.
Calculate the current in the primary coil.
current = ......................................................... [3]
[Total: 9]
5. (a) (i) State what is meant by a magnetic field.
............................................................................................................................................................
……………………...................................................................................................................... [1]
(ii) Define the direction of a magnetic field.
…………...........................................................................................................................................
…………...................................................................................................................................... [1]
(b) Fig. 8.1 shows a negatively charged metal sphere.
On Fig. 8.1, draw four lines to show the electric field and its direction. [2]
(c) Fig. 8.2 shows a circuit.
The three cells are identical and have zero resistance.
The resistors R1, R2 and R3 are identical.
The reading on the voltmeter is 6.0 V.
When the diode is conducting, it has zero resistance and zero potential difference (p.d.) across it.
(i) Determine the e.m.f. of one cell.
e.m.f. = ......................................................... [1]
(ii) Determine the ratio of the p.d. across R2 to the p.d. across R3.
..................................................................................................................................... [1]
(iii) All the cells are reversed.
1. State and explain the change in current in R1.
............................................................................................................................................................
……………………………........................................................................................................ [1]
2. Determine the new value of the ratio of the p.d. across R2 to the p.d. across R3.
……………….............................................................................................................................. [1]
[Total: 8]
6. An electric heater uses a resistance wire of resistance 26 Ω. The power dissipated in the
resistance wire is 2500 W.
(a) Calculate the current in the resistance wire.
current = ......................................................... [3]
(b) The resistance wire of the heater has a length of 1.2 m and a cross-sectional area of
7.9 × 10–7 m2. A new heater is designed using wire of the same material with length 1.8 m and cross
sectional area 5.8 × 10–7 m2.
Calculate the resistance of this wire.
resistance = ......................................................... [3]
(c) The 2500 W heater is used in a country where electricity costs 0.30 dollars per kilowatt-hour.
Calculate the cost of using the heater continuously for two days.
cost = ............................................. dollars [2]
[Total: 8]
7. The voltage across the primary coil of a 100% efficient transformer is 220 V and the voltage
across the secondary coil is 12 V.
(a) The current in the secondary coil is 2.5 A.
Calculate the current in the primary coil.
current = ......................................................... [3]
(b) Calculate the ratio of the number of turns on the primary coil to the number of turns on the
secondary coil of the transformer.
ratio = ......................................................... [2]
[Total: 5]
8. A cylinder is made of modelling clay. The modelling clay is an electrical conductor.
Fig. 8.1 shows the cylinder.
The cylinder is connected into a circuit.
Fig. 8.2 shows that the circuit also includes a battery of electromotive force (e.m.f.) 9.0 V and a
resistor P.
The resistance of P is 4.0 Ω. The current in P is 1.5 A.
(a) Calculate:
(i) the magnitude X of the charge that flows through P in 600 s
X = ......................................................... [2]
(ii) the resistance of the cylinder of modelling clay.
resistance = ......................................................... [3]
(b) The cylinder is removed from the circuit and replaced with a new cylinder made of the same
modelling clay.
The new cylinder is twice the length and has half the cross-sectional area of the first cylinder.
Calculate the time that it now takes for a charge of magnitude X to flow through resistor P.
time = ......................................................... [4]
[Total: 9]
9. Fig. 6.1 shows the circuit diagram for a flashlight (torch).
The electromotive force (e.m.f.) of the battery is 4.5 V. The circuit contains a 60 Ω fixed resistor.
The current in the light-emitting diode (LED) is 0.020 A.
(a) Calculate the potential difference (p.d.) across the LED.
p.d. = ......................................................... [2]
(b) Explain why the LED does not light up if the battery is reversed.
.............................................................................................................................................................
……………..................................................................................................................................... [1]
(c) The chemical energy stored in the battery is 1050 J.
Show that the flashlight operates for approximately 3 h.
[2]
(d) Calculate the total charge that flows through the LED in 3600 s.
charge = ......................................................... [2]
[Total: 7]
10.
Fig. 7.1 shows some uses of electromagnetic radiation and different regions of the
electromagnetic spectrum.
(a) Draw a line from each use to the correct region of the spectrum.
Each region of the spectrum is used once. One line has been completed for you. [2]
(b) State the speed of electromagnetic waves in a vacuum.
speed = ......................................................... [1]
(c) A Bluetooth headset can be used to listen to music on a mobile (cell) phone without the need
for wires to connect the headset to the phone.
(i) The headset uses frequencies in the range 2.40–2.48 GHz.
Calculate the wavelength of the radio waves when the frequency is in the middle of the frequency
range.
wavelength = ......................................................... [3]
(ii) Suggest why a Bluetooth headset only works well over short distances.
................................................................................................................................................................
.......................................................................................................................................................... [1]
[Total: 7]
11. (a) Fig. 8.1 shows the single turn coil of a simple direct current (d.c.) motor.
(i) Explain the direction of the turning effect as seen by an observer at O.
................................................................................................................................................................
................................................................................................................................................................
………………………………………............................................................................................. [2]
(ii) The coil is replaced by an otherwise identical new coil with three turns and the same
current in the coil.
State how the turning effect compares with the turning effect in (i).
.......................................................................................................................................................... [1]
(iii) A third coil is identical to the coil in (i) except that its resistance is three times greater.
The potential difference (p.d.) across the coil is the same as the p.d. in (i).
State how the turning effect compares with the turning effect in (i).
……………..................................................................................................................................... [1]
(b) Fig. 8.2 is a voltage–time graph showing the output of a simple alternating current (a.c.)
generator at times t0, t1, t2 and t3.
Fig. 8.3 is an end view of the plane of the coil of the generator at time t0. The coil is rotating
clockwise.
(i) Draw an end view of the position of the plane of the coil at time t1.
Include the labels A and B.
[1]
(ii) Draw an end view of the position of the plane of the coil at time t2.
Include the labels A and B.
[1]
(iii) Draw an end view of the position of the plane of the coil at time t3.
Include the labels A and B.
[1]
[Total: 7]
12. Fig. 6.1 shows two bar magnets.
(a) On Fig. 6.1, sketch the pattern and the direction of the magnetic field lines between the bar
magnets. [2]
(b) Fig. 6.2 shows the same bar magnets with a coil of wire between them.
(i) Name the parts labelled A in Fig. 6.2.
....................................................................................................................................................... [1]
(ii) The coil of wire is rotated in the direction shown in Fig. 6.2.
On Fig. 6.2, draw an arrow to show the direction of the current in the coil. Explain your answer.
.............................................................................................................................................................
………………………..................................................................................................................... [2]
(iii) Explain how rotating the coil in Fig. 6.2 continuously causes the galvanometer needle to
show an alternating current.
.............................................................................................................................................................
.............................................................................................................................................................
.............................................................................................................................................................
.............................................................................................................................................................
...................................................................................................................................................... [4]
[Total: 9]
13. Fig. 7.1 shows a circuit including a 12 V battery and two identical lamps.
(a) The 12 V battery consists of cells connected in series. Each cell in the battery has an
electromotive force (e.m.f.) of 1.5 V. Determine how many cells are in the battery.
number of cells = ..................................................... [1]
(b) (i) When the switch is closed, the ammeter reading is 2.4 A.
Calculate the total resistance of the circuit.
resistance = ..................................................... [2]
(ii) Each lamp has a resistance of 3.0 Ω.
Calculate the resistance of Q.
resistance of Q = ..................................................... [2]
(c) (i) On Fig. 7.1, draw the symbol for a voltmeter that measures the potential difference (p.d.)
across the two lamps. [1]
(ii) Calculate the power supplied to one lamp.
power = ..................................................... [3]
[Total: 9]
14. A radio is connected to the mains supply using a step-down transformer.
(a) Draw a labelled diagram of the structure of a basic step-down transformer.
[3]
(b) Explain the operation of a basic transformer.
................................................................................................................................................................
................................................................................................................................................................
................................................................................................................................................................
……………………………….,..................................................................................................... [3]
(c) The voltage of the mains supply is 230 V. The output voltage of the transformer is 6.0 V.
Calculate the value of the turns ratio (Ns/Np).
Give your answer to two significant figures.
value of turns ratio = ..................................................... [2]
[Total: 8]
15. Fig. 7.1 shows a small plotting compass which is aligned with the magnetic field between
magnetic poles A and B of a U-shaped magnet.
(a) State the polarity of the poles.
pole A ........................................................................................................................................
pole B .......................................................................................................................................[1]
(b) Fig. 7.2 shows a wire, placed between two poles, carrying a current in the direction of the
arrow.
On Fig. 7.2, draw an arrow to show the direction of the force on the wire due to the magnetic
field. [2]
(c) Fig. 7.3 shows a β-particle moving in the direction of the arrow between the same two poles.
On Fig. 7.3, draw an arrow to show the direction of the force on the β-particle due to the
magnetic field.
[2]
[Total: 5]
16. Fig. 8.1 shows how the electromotive force (e.m.f.) of a 60 Hz alternating current (a.c.) power
supply varies with time.
(a) Calculate the time period of the a.c.
time period = ......................................................... [1]
(b) Fig. 8.2 shows this power supply connected in a circuit.
(i) State the name of component A.
.......................................................... [1]
(ii) In each time period of the a.c., 1.5 × 1017 electrons pass through component A.
The charge on an electron is 1.6 × 10–19 C.
Calculate the average current in the circuit during one time period.
current = ......................................................... [3]
(c) On Fig. 8.3:
1. mark, with an arrow labelled E, the direction of the electron flow through component B
2. mark, with an arrow labelled I, the direction of the conventional current in component C.
[2]
(d) Fig. 8.4 shows a circuit with components B and C connected to a direct current (d.c.) power
supply of e.m.f. 12 V.
The current in the circuit is 0.35 A.
Calculate the power delivered by the power supply to the circuit.
power = ......................................................... [2]
[Total: 9]
17. Fig. 9.1 shows a circuit with a 3-position switch.
The moving part of the switch is always connected to point Y around which it pivots.
The other end of the moving part, labelled X, can be connected to one of the points A, B or C.
(a) The resistance of the motor is 2.0 Ω and the resistance of the resistor is 3.0 Ω.
Determine the current in the motor when the switch is connected to:
(i) point A
current = ......................................................... [1]
(ii) point B
current = ......................................................... [2]
(iii) point C.
current = ......................................................... [2]
(b) Two resistors of resistance 2.0 Ω and 3.0 Ω are connected in parallel.
Calculate the combined resistance of the resistors in this arrangement.
resistance = ......................................................... [3]
[Total: 8]
18. (a) Fig. 8.1 shows a circuit.
(i) State the name of component X.
……………..................................................................................................................................... [1]
(ii) The potential difference (p.d.) across component Y is measured with a voltmeter.
On Fig. 8.1, draw the symbol for the voltmeter and its connections to the circuit. [1]
(iii) The electromotive force (e.m.f.) of the battery is 12 V. Component Y has a resistance of 400 Ω.
In a brightly lit room, the resistance of component X is 350 Ω.
1. Calculate the current in the circuit.
current = ......................................................... [2]
2. Calculate the p.d. across component Y.
p.d. = ......................................................... [1]
(iv) In a dark room, the resistance of component X is very large.
State the effect this will have on the p.d. across component Y.
......................................................................................................................................................... [1]
(b) Suggest a practical use for component X.
………............................................................................................................................................. [1]
[Total: 7]
19. (a) Fig. 9.1 shows a magnet on the end of a spring and a coil of wire connected to a sensitive
centre-zero galvanometer. The magnet can move freely through the coil.
(i) The magnet is pulled down and released.
Describe and explain what happens to the needle of the sensitive galvanometer.
................................................................................................................................................................
................................................................................................................................................................
................................................................................................................................................................
.......................................................................................................................................................... [4]
(ii) The magnet is replaced with a stronger magnet.
State the effect of using a stronger magnet on what happens to the needle of the galvanometer.
…………..................................................................................................................................... [1]
(b) A step-up transformer is used to step up the output voltage of a power station from 25000 V to
400000 V for transmission along power lines. The number of turns on the secondary coil is 36000.
Calculate the number of turns on the primary coil.
\
number of turns = ......................................................... [2]
[Total: 7]
20. The lamp of a car headlight is rated at 12 V, 50 W.
Calculate the current in the lamp when operating normally.
current = ......................................................... [2]
(b) A car is driven at night.
In a journey, the total charge that passes through the 12 V battery is 270 kC.
(i)
Calculate the electrical energy transferred.
energy = ......................................................... [3]
(ii) The fuel used by the car provides 3.6 × 104 J / cm3.
Calculate the volume of fuel used to provide the energy calculated in (b)(i).
volume = ......................................................... [2]
[Total: 7]
21. Fig. 9.1 shows current-potential difference graphs for a resistor and for a lamp.
(a) (i) The potential difference (p.d.) applied to the resistor is increased. Tick the box that
indicates the effect on the resistance of the resistor.
(ii) The potential difference (p.d.) applied to the lamp is increased. Tick the box that indicates
the effect on the resistance of the lamp.
(b) The p.d. across the lamp is 6.0 V. Calculate the resistance of the lamp.
resistance = ......................................................... [2]
(c) The lamp and the resistor are connected in parallel to a 6.0 V supply.
Calculate the current from the supply.
current = ......................................................... [2]
(d) The lamp and the resistor are connected in series to another power supply. The current in
the circuit is 4.0 A.
Calculate the total p.d. across the lamp and the resistor.
p.d. = ......................................................... [2]
[Total: 8]
22. (a) Fig. 10.1 shows a straight wire AB placed in the magnetic field between the poles of a
magnet. The ends of AB are connected to a galvanometer.
When AB is moved vertically, the needle of the galvanometer shows a deflection.
State three factors that affect the size of the deflection.
1 ...............................................................................................................................................
2 ...............................................................................................................................................
3 ..............................................................................................................................................[3]
(b) Fig. 10.2 shows a transformer.
(i) The primary coil P has 8000 turns and an input of 240 V. The secondary coil S has an
output of 12 V.
Calculate the number of turns in the secondary coil.
number = ......................................................... [2]
(ii) A circuit containing a resistor is connected to the terminals A and B.
A direct current (d.c.) is required in this resistor.
On Fig. 10.2, draw this circuit.
[1]
[Total: 6]
23. (a) (i) Fig. 8.1 shows a positively charged cube of insulating material. The cube is fixed to a
piece of wood that is floating on water. A negatively charged rod is held above the piece
of wood and brought close to the cube, as shown.
State and explain any movement of the piece of wood.
................................................................................................................................................................
................................................................................................................................................................
................................................................................................................................................................
..........................................................................................................................................................[2]
(ii) Fig. 8.2 shows two cubes of insulating material. One is positively charged and the other
is negatively charged. The cubes are fixed to a piece of wood that is floating on water.
Charged rods are held above the piece of wood and brought close to the cubes, as
shown.
State and explain any movement of the piece of wood.
................................................................................................................................................................
................................................................................................................................................................
................................................................................................................................................................
...........................................................................................................................................................[2]
(b) In terms of a simple electron model, describe the differences between conductors and
insulators.
conductors .............................................................................................................................................
................................................................................................................................................................
..............................................................................................................................................................
insulators ...............................................................................................................................................
...............................................................................................................................................................
..........................................................................................................................................................[2]
(d) On Fig. 8.3, draw the electric field pattern around a single point positive charge.
24. Fig. 9.1 shows a permanent bar magnet next to a circuit that contains a coil and a galvanometer.
(a) Suggest a metal from which the magnet is made.
...............................................................................................................................................[1]
(b) The magnet is moved to the left and inserted a small distance into the coil. The galvanometer
deflects briefly and shows that there is a current in the coil.
(i) Explain why there is a current in the coil.
................................................................................................................................................................
................................................................................................................................................................
................................................................................................................................................................
...........................................................................................................................................................[2]
(ii) As the magnet is moving near to the coil, end Q of the coil behaves as a magnetic pole.
State the polarity of end Q and explain why it has this polarity.
................................................................................................................................................................
................................................................................................................................................................
...........................................................................................................................................................[2]
(c) Suggest two ways in which the deflection of the galvanometer can be reversed.
1. ............................................................................................................................................................
...............................................................................................................................................................
2. .........................................................................................................................................................
...........................................................................................................................................................[2]
[Total: 7]
25. (a) Describe how a direct current (d.c.) differs from an alternating current (a.c.).
................................................................................................................................................................
..........................................................................................................................................................[1]
(b) Fig. 9.1 shows how the voltage output of an a.c. generator varies with time.
A heater is connected directly to the a.c. generator and the maximum current in the heater is
0.75 A.
(i) On Fig. 9.2, sketch a graph to indicate how the current in the heater varies with time.
(ii)
Calculate the power produced by the heater when the current is 0.75 A.
power = ...........................................................[2]
(c) Fig. 9.3 shows the coil ABCD of the a.c. generator between two magnetic poles.
(i) On Fig. 9.3, draw a straight arrow to indicate the direction in which side AB of the coil is
moving. Label this arrow M.
[1]
(ii) Deduce the direction of the current induced in side AB of the coil and explain your
reasoning.
................................................................................................................................................................
................................................................................................................................................................
................................................................................................................................................................
..........................................................................................................................................................[2]
(iii) The rate at which the coil of the a.c. generator rotates increases.
State two ways in which the alternating voltage changes.
1. ...........................................................................................................................................................
................................................................................................................................................................
2. ...................................................................................................................................... ....................
........................................................................................................................................... ..............[2]
[Total: 9]