IGCSE Physics 0625 — Topic 4: Electricity and Magnetism

Question 1

A steel paperclip is placed near a bar magnet. The paperclip is attracted and sticks to the magnet. When the magnet is removed, the paperclip can attract another paperclip.

Which statement explains this?

AThe paperclip has become a permanent magnet by induced magnetism BThe paperclip was already magnetised before the experiment CThe paperclip became an electromagnet DThe magnetic field of the Earth magnetised the paperclip

Question 2

Two bar magnets are placed end-to-end with their North poles facing each other, 10 cm apart. A plotting compass is placed at point X, exactly at the midpoint between them.

What does the compass needle do?

APoints toward the left magnet BPoints toward the right magnet CPoints toward geographic north DAligns perpendicular to the line joining the magnets

Question 3

An electromagnet with a steel core is used at Southampton docks to sort scrap metal. When the current is switched off, the steel core remains magnetised and metal pieces cannot be released.

Which change would solve this problem?

AIncrease the number of coil turns BReplace the steel core with a soft iron core CIncrease the current DUse thicker wire for the coil

Question 4

The diagram shows a solenoid connected to a battery. The current direction is marked. Point P is at the left end of the solenoid.

Which statement correctly describes the magnetic field at point P?

APoint P is a north pole and the field lines emerge from it BPoint P is a south pole and the field lines enter it CThe field is zero at point P DThe field direction depends on the thickness of the wire

Question 5

A student in Edinburgh places a bar magnet under a sheet of paper and sprinkles iron filings on top. She observes the pattern formed by the filings.

Which statement about the iron filings pattern is correct?

AThe filings show the direction of the magnetic field BThe filings show the shape of the magnetic field but not its direction CThe filings are most concentrated where the field is weakest DThe filings align parallel to the field at all points, showing both shape and direction

Question 6

A relay is used in a burglar alarm circuit in a Manchester warehouse. The relay has a soft iron armature.

Why is soft iron used for the armature instead of steel?

ASoft iron is a better electrical conductor than steel BSoft iron is more easily magnetised and demagnetised than steel CSoft iron is stronger than steel DSoft iron is cheaper than steel

Question 7

A magnetic field line diagram is drawn for a bar magnet.

Which statement about the field lines is NOT correct?

AField lines go from north to south outside the magnet BField lines are closest together where the field is strongest CField lines can cross each other at the neutral point DThe field is three-dimensional but diagrams show a two-dimensional cross-section

Question 8

Two long, parallel wires in a Cambridge laboratory carry current in the same direction. What do the wires do?

AAttract each other BRepel each other CNeither attract nor repel DAttract if the currents are equal, repel if unequal

Question 9

A charge of 450 C passes through a lamp in 3 minutes. What is the current?

A150 A B2.5 A C7.5 A D1350 A

Question 10

A student measures the resistance of a wire. She records a current of 0.40 A when the p.d. across the wire is 2.4 V. She then doubles the length of wire. If the wire obeys Ohm's law, what is the new current when the same p.d. is applied?

A0.80 A B0.40 A C0.20 A D0.10 A

Question 11

The graph shows how current varies with potential difference for component X. The graph is a straight line through the origin.

Which component could X be?

AA filament lamp BA diode CA thermistor at constant temperature DA light-dependent resistor in varying light

Question 12

An electric heater is rated at 2.0 kW, 230 V. What is the current it draws?

A460 000 A B115 A C8.7 A D0.12 A

Question 13

A household in Bristol uses a 3 kW immersion heater for 2.5 hours every day. Electricity costs 28p per kWh. What is the daily cost of using the heater?

A21p B£2.10 C£210 D£0.84

Question 14

Two resistors of 6 Ω and 3 Ω are connected in parallel. What is their combined resistance?

A9 Ω B4.5 Ω C2 Ω D0.5 Ω

Question 15

The e.m.f. of a battery is 12 V. When it delivers a current of 2 A, the terminal p.d. is 11 V. What is the internal resistance of the battery?

A5.5 Ω B6.0 Ω C0.5 Ω D1.0 Ω

Question 16

A 60 W filament lamp and a 15 W LED lamp both produce similar light output. Both are used for 8 hours. How much more energy does the filament lamp use compared to the LED?

A45 J B360 J C0.36 kWh D360 kWh

Question 17

An electric kettle is rated 230 V, 2.8 kW. How long does it take to transfer 504 kJ of energy?

A180 s B3 s C1 411 200 s D0.18 s

Question 18

Which statement about potential difference is correct?

APotential difference is the work done per unit current BPotential difference is the energy transferred per unit charge CPotential difference is always the same as e.m.f. DPotential difference is measured in amperes

Question 19

A wire of cross-sectional area A and length L has resistance R. A second wire of the same material has cross-sectional area 2A and length 3L. What is its resistance?

A6R B1.5R C0.75R D3R

Question 20

A battery drives a current of 0.5 A through a 12 Ω resistor for 10 minutes. How much energy is transferred to the resistor?

A60 J B1800 J C3600 J D36 000 J

Question 21

In the circuit shown, a 6 V battery is connected to a 4 Ω resistor and a 12 Ω resistor in series. What is the p.d. across the 12 Ω resistor?

A3.0 V B4.5 V C1.5 V D6.0 V

Question 22

A potential divider circuit uses a thermistor and a 1 kΩ fixed resistor connected in series to a 5 V supply. The output voltage is taken across the fixed resistor.

When the temperature increases, what happens to the output voltage?

AIncreases, because the thermistor resistance decreases so more voltage is across the fixed resistor BDecreases, because the thermistor resistance decreases CStays the same, because the supply voltage is constant DDecreases, because the thermistor gets hotter and conducts better

Question 23

Three identical lamps, each of resistance 6 Ω, are connected: two in parallel with each other, and this parallel combination is in series with the third lamp. They are connected to a 12 V battery of negligible internal resistance.

What is the current through each of the parallel lamps?

A2.0 A B1.33 A C0.67 A D4.0 A

Question 24

An LDR is connected in a potential divider circuit with a fixed resistor to control a buzzer in a street lamp system in Leeds. The buzzer should sound when it gets dark.

Which arrangement works correctly?

AOutput taken across the fixed resistor — voltage increases in the dark BOutput taken across the LDR — voltage increases in the dark COutput taken across the fixed resistor — voltage decreases in the dark DLDR connected directly to the buzzer with no other components

Question 25

In a circuit, an ammeter reads 0.50 A. The ammeter has a resistance of 0.10 Ω. The true current without the ammeter would be slightly different.

Which statement is correct?

AThe ammeter reading is exactly the true current because ammeters have zero resistance BThe ammeter causes a slight decrease in current due to its resistance CThe ammeter causes a slight increase in current DThe ammeter resistance has no effect because it is connected in parallel

Question 26

A student sets up a circuit with a variable resistor (rheostat), an ammeter, and a fixed resistor to investigate how current varies with voltage across the fixed resistor. She plots current (y-axis) against voltage (x-axis). The graph is a straight line that does NOT pass through the origin.

What is the most likely reason?

AThe fixed resistor does not obey Ohm's law BThere is a systematic error — the voltmeter has a zero error CThe ammeter is connected in the wrong place DThe resistor is heating up

Question 27

A circuit contains a 12 V battery, a switch, a lamp, and a fuse, all in series. A voltmeter is connected across the lamp. When the switch is open, the voltmeter reads 12 V. When the switch is closed, it reads 10 V.

Which explanation is correct?

AThe battery has internal resistance, causing a 2 V drop when current flows BThe voltmeter is faulty CThe fuse has negligible resistance DThe lamp has zero resistance when the switch is open

Question 28

A student connects three resistors: R₁ = 2 Ω, R₂ = 3 Ω, and R₃ = 6 Ω. R₂ and R₃ are in parallel, and this combination is in series with R₁. What is the total resistance?

A11 Ω B4 Ω C1 Ω D0.83 Ω

Question 29

A 2.5 kW electric shower is connected to a 230 V supply. Which fuse rating should be used?

A3 A B5 A C10 A D13 A

Question 30

Which wire in a three-pin plug is connected to the fuse?

AEarth (green/yellow) BNeutral (blue) CLive (brown) DBoth live and neutral

Question 31

A metal-cased toaster develops a fault where the live wire touches the metal case. The toaster is correctly earthed. What happens?

AThe fuse blows because a large current flows through the earth wire BThe user gets a shock because the earth wire has too much resistance CNothing happens because the neutral wire carries the current safely DThe toaster continues to work normally

Question 32

Double-insulated appliances do not need an earth wire. Which statement explains why?

AThey use lower voltages so are safe without earthing BTheir outer casing is made of an insulating material, so the user cannot touch any live component CThey have thicker live and neutral wires DThey contain an internal fuse that replaces the earth connection

Question 33

A transformer has 200 turns on the primary coil and 1000 turns on the secondary coil. The primary voltage is 25 V. Assuming the transformer is ideal, what is the secondary voltage?

A5 V B50 V C125 V D5000 V

Question 34

The National Grid transmits electrical power at 400 kV instead of 25 kV from the power station. By what factor does this reduce the current in the transmission cables, assuming the same power is transmitted?

A4 B16 C256 D400

Question 35

A rectangular coil is rotated in a uniform magnetic field in an AC generator. The graph shows how the e.m.f. varies with time. At time T, the e.m.f. is zero.

What is the position of the coil at time T?

AThe plane of the coil is parallel to the magnetic field BThe plane of the coil is perpendicular to the magnetic field CThe coil is at 45° to the magnetic field DThe coil has stopped rotating

Question 36

A transformer used in a phone charger converts 230 V to 5 V. The charger delivers a current of 2 A. If the transformer is 80% efficient, what current does it draw from the mains?

A0.043 A B0.054 A C92 A D18.4 A

Question 37

A simple DC motor consists of a rectangular coil in a magnetic field. The coil rotates when current flows. What is the purpose of the split-ring commutator?

ATo increase the speed of rotation BTo reverse the current direction in the coil every half turn so it continues rotating in the same direction CTo increase the magnetic field strength DTo connect the motor to the power supply

Question 38

In a step-down transformer, the primary coil has 4600 turns and the secondary has 240 turns. The input voltage is 230 V. The transformer is used to power a 12 V, 36 W lamp. It is 90% efficient.

What is the current in the primary coil?

A0.17 A B3.0 A C0.16 A D1.74 A

Question 39

Lenz's law states that the direction of an induced e.m.f. is such that it opposes the change producing it. A bar magnet is dropped through a vertical copper tube.

What happens to the speed of the magnet?

AIt accelerates due to gravity and is unaffected by the tube BIt falls more slowly than in free fall because induced currents create an opposing magnetic field CIt stops inside the tube DIt speeds up because the copper tube focuses the magnetic field

Question 40

A generator at a Scottish wind farm produces an e.m.f. that varies sinusoidally with a peak of 340 V and a frequency of 50 Hz. What is the time period of the output?

A50 s B0.50 s C0.020 s D0.050 s

Paper 2 — Multiple Choice

Section A: Magnetism

Section B: Electrical Quantities

Section C: Circuits

Section D: Electrical Safety

Section E: Electromagnetic Effects