AQA GCSE Physics 8463: Magnetism and electromagnetism – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions cover Topic 7, Magnetism and electromagnetism (sections 4.7.1 to 4.7.3), of the AQA GCSE Physics (8463) specification, for first teaching 2016 with exams from June 2018 (version 1.1). The topic is examined on Paper 2 at Foundation and Higher tier every May/June. Questions 1 to 5 are for both tiers. Questions 6 to 12 test “(HT only)” statements and are labelled (Higher tier only).

Learn the content first in the study guide and the revision notes. The course hub is AQA GCSE Physics and the printable checklist lists every statement.

Questions

1.

(a) State what happens when the north pole of one bar magnet is brought close to the north pole of another. [1] (b) Give two differences between a permanent magnet and an induced magnet. [2] (c) Name two magnetic elements other than iron. [1]

2.

(a) Describe how to use a plotting compass to draw the magnetic field pattern of a bar magnet. [3] (b) State where the magnetic field of a bar magnet is strongest. [1] (c) State the direction of magnetic field lines outside a bar magnet. [1]

3. Explain how the behaviour of a magnetic compass gives evidence that the Earth’s core is magnetic. [2]

4. A long straight wire passes vertically through a horizontal card.

(a) Describe how you could show that a current in the wire produces a magnetic field. [2] (b) Describe the shape of the magnetic field around the wire, and how its strength changes with distance. [2] (c) The wire is then wound into a solenoid. Give two ways to make the magnetic field of the solenoid stronger without changing the number of turns. [2]

5. In a relay, circuit A has a switch and a coil on an iron core. A pivoted iron armature, held by a spring, sits next to the core; when it moves, it closes contacts in circuit B, which contains a motor.

Explain how closing the switch in circuit A starts the motor, and what happens when the switch is opened. [4]

6. (Higher tier only)

(a) State what the first finger, second finger and thumb represent in Fleming’s left-hand rule. [2] (b) State what happens to the force on a wire if both the current and the magnetic field are reversed. [1] (c) State two factors that affect the size of the force on a current-carrying wire at right angles to a magnetic field. [2]

7. (Higher tier only) A wire carrying a current of 4.0 A is at right angles to a magnetic field of flux density 0.25 T. The length of wire in the field is 8.0 cm.

(a) Calculate the force on the wire. [3] (b) Calculate the current needed to give a force of 0.050 N on the same wire. [2]

8. (Higher tier only) A rectangular coil carrying a current is placed between the poles of a magnet, with two sides of the coil at right angles to the field.

(a) Explain why the coil rotates. [3] (b) Give two ways to make the coil rotate faster. [2]

9. (Higher tier only) A moving-coil loudspeaker and microphone each have a coil attached to a cone or diaphragm, inside a permanent magnet’s field.

(a) Explain how the loudspeaker produces a sound wave from an alternating current. [4] (b) Explain how the microphone produces a varying current from a sound wave. [3]

10. (Higher tier only) A bar magnet is pushed into a coil connected to a sensitive ammeter. The ammeter needle moves to the right.

(a) State what the ammeter shows while the magnet is held still inside the coil. [1] (b) State what the ammeter shows as the magnet is pulled back out. [1] (c) Give two ways to increase the induced current. [2] (d) Explain why it takes more force to push the magnet in when the coil is connected to the ammeter than when the circuit is broken. [2]

11. (Higher tier only)

(a) Describe the graph of potential difference against time for an alternator. [2] (b) State how the graph for a dynamo differs. [1] (c) The alternator is turned twice as fast. Describe two changes to its graph. [2]

12. (Higher tier only) A power station generator produces a p.d. of 25 kV. A transformer with 1500 turns on its primary coil and 24 000 turns on its secondary coil connects it to the transmission cables. The power transmitted is 50 MW. Assume the transformer is 100% efficient.

(a) Explain how the transformer produces a p.d. across its secondary coil. [3] (b) Calculate the p.d. across the secondary coil. [2] (c) Calculate the current in the transmission cables. [2] (d) Calculate the current in the primary coil. [2] (e) The cables have a total resistance of 4.0 Ω. Calculate the power wasted in the cables and explain why transmitting at high p.d. is an advantage. [3]

Answers

1. (a) They repel [1]. (b) Permanent: own field all the time; induced: magnetic only while in another field [1]. Permanent can attract or repel; induced is always attracted (or: loses its magnetism quickly when removed) [1]. (c) Cobalt and nickel (both needed) [1]. [4] Examiner insight: A difference needs both sides stated; “an induced magnet is temporary” alone may not score.

2. (a) Place the compass near one pole and mark the direction the needle points [1]. Move the compass so its tail is at the mark and mark again, repeating until reaching the other pole [1]. Join the marks with a smooth line and repeat from other starting points [1]. (b) At the poles [1]. (c) From north to south [1]. [5] Examiner insight: Method marks need the “tail on the last mark” step; “move the compass around the magnet” is too vague.

3. A compass needle is a small magnet that points along the Earth’s magnetic field [1]. It does this everywhere on Earth, so the Earth must have a magnetic field from a magnetic core [1]. [2] Examiner insight: Two linked points are needed; “compasses point north” alone gains nothing.

4. (a) Place a compass on the card next to the wire; it deflects when the current is switched on [1]. It deflects the other way when the current is reversed (or iron filings form circles) [1]. (b) Concentric circles centred on the wire [1]; the field gets weaker further from the wire (circles further apart) [1]. (c) Increase the current [1]; add an iron core [1]. [6] Examiner insight: “More turns” is excluded by the question, so it scores nothing; read the constraint.

5. Closing the switch makes a current flow in the coil [1], so the iron core becomes an electromagnet [1]. It attracts the armature, which closes the contacts, so the motor starts [1]. When the switch opens, the core loses its magnetism and the spring pulls the armature back, stopping the motor [1]. [4] Examiner insight: Each link in the chain is a separate mark; skipping “core becomes magnetised” breaks the sequence.

6. (a) First finger: magnetic field; second finger: current [1]. Thumb: force (motion) [1]. (b) It stays in the same direction (unchanged) [1]. (c) Any two: magnetic flux density; current; length of wire in the field [1] [1]. [5] Examiner insight: “Magnet strength” is accepted for flux density, but “bigger magnet” usually is not.

7. (a) l = 8.0 cm = 0.080 m [1]; F = B I l = 0.25 × 4.0 × 0.080 [1] = 0.080 N [1] (b) I = F / (B l) = 0.050 / (0.25 × 0.080) [1] = 2.5 A [1] [5] Examiner insight: An answer of 8.0 N from using 8.0 cm loses the conversion and final marks; the substitution mark may still be given.

8. (a) The current flows in opposite directions in the two sides of the coil [1], so the forces on the two sides act in opposite directions (one up, one down) [1]. This gives a turning effect, so the coil rotates [1]. (b) Increase the current [1]; use a stronger magnet (or more turns) [1]. [5] Examiner insight: “A force acts on the coil” does not explain rotation; the forces on the two sides must be opposite.

9. (a) The alternating current flows in the coil in the magnet’s field, so a force acts on the coil (motor effect) [1]. As the current changes direction, the force changes direction [1], so the coil and cone vibrate [1]. The vibrating cone produces pressure variations in the air, which is the sound wave [1]. (b) The sound wave’s pressure variations make the diaphragm and coil vibrate [1]. The coil moves in the magnetic field, so a p.d. is induced across it (generator effect) [1]. This produces a current that varies in the same pattern as the sound [1]. [7] Examiner insight: Naming the motor effect for (a) and the generator effect for (b) is expected; swapping them loses the mark in both parts.

10. (a) Zero / no reading [1]. (b) The needle moves to the left [1]. (c) Move the magnet faster [1]; use a stronger magnet or more turns on the coil [1]. (d) The induced current produces its own magnetic field [1] that opposes the motion of the magnet (repels it), so extra work is needed [1]. [6] Examiner insight: In (a), “no current because the magnet is not moving” is right; “no current because it is inside the coil” is not.

11. (a) A wave-shaped (regular) curve [1] that alternates between positive and negative p.d. [1]. (b) The dynamo’s p.d. never goes negative; it stays on one side of the time axis [1]. (c) The peak p.d. is higher [1]; the cycles are closer together (twice as many per second) [1]. [5] Examiner insight: Both changes are needed for the two marks; many answers give only the frequency change.

12. (a) An alternating current in the primary produces a changing magnetic field in the iron core [1]. The changing field passes through the secondary coil [1] and induces an alternating p.d. across it [1]. (b) Vs = Vp × ns / np = 25 000 × 24 000 / 1500 [1] = 400 000 V = 400 kV [1] (c) I = P / V = 50 × 10⁶ / 400 000 [1] = 125 A [1] (d) Ip = P / Vp = 50 × 10⁶ / 25 000 [1] = 2000 A [1] (e) Power wasted = I² R = 125² × 4.0 = 62 500 W (62.5 kW) [1]. At 25 kV the current would be 2000 A, wasting 16 MW [1]. A higher p.d. gives a lower current for the same power, so much less energy is wasted heating the cables [1]. [12] Examiner insight: Errors in (b) and (c) are carried forward, so show every substitution; (e) must link higher p.d. to lower current, not lower resistance.

Where marks are usually lost

• Field lines without arrows, or pointing S to N.
• Saying a magnet can repel an unmagnetised piece of iron.
• Not converting cm to m before F = BIl.
• Motor explanations with no mention of opposite forces on opposite sides of the coil.
• Swapping the motor effect and the generator effect for loudspeakers and microphones.
• Claiming a p.d. is induced while the magnet is stationary.
• Transformer explanations that leave out “alternating” or “changing”.
• Saying high-voltage transmission reduces resistance.

Next steps

• Magnetism and electromagnetism revision notes
• Magnetism and electromagnetism study guide
• Waves practice questions
• AQA GCSE Physics course hub
• Printable checklist
• All free 10-minute diagnostics
• Book a free trial class

Official syllabus

AQA GCSE Physics (8463) specification, for first teaching 2016, exams from June 2018, version 1.1 (30 September 2019), published by AQA – section 4.7 Magnetism and electromagnetism.