AQA GCSE Combined Science: Trilogy Physics Paper 2 (Higher), 2022: Question 4

💡 Key knowledge you need

• A permanent magnet produces a magnetic field.
• A current in a wire also produces a magnetic field.
• When these magnetic fields interact, a force acts on the wire: this is the motor effect.
• Fleming’s left-hand rule predicts the direction of the force.
• A larger current, more turns on the coil, or a stronger magnet increases the force on the coil.

🧠 Exam technique

• For “explain why”, give the cause and the scientific reason.
• For “direction” questions, mention Fleming’s left-hand rule by name.
• For motor improvements, do not just name a change — link it to increased force and therefore faster rotation.

✅ Correct answer

There is a magnetic field due to the permanent magnets, and the current in the wire produces a magnetic field. These magnetic fields interact, so there is a force on the wire.

💡 Key knowledge

• A wire carrying current has its own magnetic field around it.
• The space between the N and S poles already has a magnetic field from the magnets.
• The force happens because the two magnetic fields interact.

🧠 How to secure both marks

• Mention both magnetic fields.
• If you only say “because of magnetism” or “because of the motor effect”, that is too vague.
• Best answers clearly state: magnet field + wire field .

❌ Common errors

• Saying the current “is attracted to the magnet”.
• Forgetting that the wire also makes a magnetic field.
• Writing about voltage or resistance — neither explains the force here.

✅ Correct answer

Use Fleming’s left-hand rule. Put your first finger in the direction of the magnetic field lines, and your second finger in the direction of the current. Your thumb then shows the direction of the force.

For this diagram, the force is downwards.

💡 Key knowledge

• Fleming’s left-hand rule is used for motors.
• First finger = magnetic field.
• Second finger = current.
• Thumb = force or motion.

🧠 Examiner insight

• Top answers did not just name the rule — they explained how to use it.
• The mark scheme allows answers that describe the three digits at right angles to each other.
• If you apply the rule to the diagram correctly, downwards is accepted.

❌ Common errors

• Using the right-hand rule instead of the left-hand rule.
• Mixing up which finger stands for field and current.
• Not linking the thumb to the force.
• Giving only “downwards” without explaining the rule may miss marks.

📐 No calculation here — but do this step by step

1. Identify the magnetic field direction: from N to S.
2. Identify the current direction from the arrow on the wire.
3. Apply Fleming’s left-hand rule.
4. Read off the thumb direction for the force.

✅ Correct answers

Any one of these changes gains the first mark:

• Use more turns of wire on the coil.
• Increase the current in the coil.
• Use a stronger magnet.

Then explain why: this increases the force on the coil due to the motor effect, so the coil rotates faster.

💡 Key knowledge

• A bigger force on the sides of the coil gives a greater turning effect.
• More turns means more wire in the magnetic field, so the effect is larger.
• Increasing current strengthens the magnetic field around the coil.
• A stronger magnet means a stronger external magnetic field.

🧠 Best exam-style sentence

“Use a stronger magnet. This increases the magnetic field strength, so the force on the coil is bigger and the coil rotates faster.”

You only need one method, but you must include the explanation for full marks.

❌ Common errors

• Saying “use a bigger magnet” — the mark scheme says ignore bigger magnet. It must be stronger magnet.
• Giving a change but not explaining why it helps.
• Saying “move the magnet” without making clear that the coil is closer to the magnet / field is stronger.

✅ 04.1 model answer

The permanent magnets produce a magnetic field. The current in the wire also produces a magnetic field, and the interaction of these magnetic fields causes a force on the wire.

✅ 04.2 model answer

Use Fleming’s left-hand rule. Put the first finger in the direction of the magnetic field and the second finger in the direction of the current. The thumb then shows the direction of the force, which is downwards.

✅ 04.3 model answer

Increase the current in the coil. This increases the force on the coil due to the motor effect, so the coil rotates faster.

💡 Can you remember?

• Why does a current-carrying wire feel a force in a magnetic field?
• Which hand is used for motors?
• What do the first finger, second finger, and thumb represent?
• How can you make a motor spin faster?

🧠 Final tip

In AQA physics questions on the motor effect, short precise answers score best. Learn the key phrases: magnetic field from magnets , current produces magnetic field , Fleming’s left-hand rule , increases force on the coil .