AQA GCSE Combined Science: Trilogy Physics Paper 2 (Higher), 2021: Question 4

15 marks · Standard Demand difficulty · Short Answer

Answer a series of short questions about permanent magnets, electromagnets, magnetic materials, the motor effect, magnetic flux density calculations, and Fleming's left-hand rule.

Practise this question

Question

A physics exam page with question 04 split into parts 04.1 to 04.7. Figure 4 shows a bar magnet labelled N on the left and S on the right with curved magnetic field lines around it; students are asked where the magnetic field is strongest and how the diagram shows field strength varies. Figure 5 shows an electromagnet above a conveyor belt separating pieces of metal, followed by questions about why an electromagnet is used, naming two other magnetic metals, and how to increase the force on iron or steel if the electromagnet design cannot be changed. Figure 6 shows a simple electric motor with magnets, a wire segment labelled AB, and a battery; students must calculate magnetic flux density from force, current, and wire length. Figure 7 shows a left hand diagram for Fleming's left-hand rule with blank labels for the directions of magnetic field, current, and force.
Question text

04 Figure 4 shows the magnetic field pattern around a permanent magnet.

Figure 4

04.1 Where is the magnetic field of the magnet the strongest?

[1 mark]

04.2 How does Figure 4 show that the strength of the magnetic field is not the same at

all places?

[1 mark]

Figure 5 shows an electromagnet being used to separate iron and steel from

non-magnetic metals.

Figure 5

04.3 Explain one reason why an electromagnet is used instead of a permanent magnet.

[2 marks]

04.4 Pieces of iron and steel are attracted to the electromagnet.

Name two other metals that would be attracted to the electromagnet.

[2 marks]

04.5 The design of the electromagnet cannot be changed.

Give two ways the force exerted by the electromagnet on a piece of iron or steel

could be increased.

[2 marks]

The conveyor belt that moves the pieces of metal is driven by an electric motor.

*13* Figure 6 shows a simple electric motor.

Figure 6

04.6 The length of the wire AB in the magnetic field is 120 mm.

There is a current of 4.0 A in the wire. The length of wire AB experiences a

force of 0.36 N.

Calculate the magnetic flux density between the magnets.

Give the unit.

[5 marks]

Magnetic flux density = Unit

04.7 Fleming’s left-hand rule can be used to determine the direction of the force on

wire AB.

*14* Complete the labels on Figure 7 to show Fleming’s left-hand rule.

[2 marks]

Figure 7

Mark scheme

Show the mark scheme The mark scheme is a table listing answers for parts 04.1 to 04.7 with marks and AO/specification references. Correct responses include: field strongest at the poles; varying distance between field lines shows varying field strength; an electromagnet can be switched off or demagnetised so separated metal can be removed; cobalt and nickel are also attracted; increasing current or bringing the electromagnet closer increases force. For the calculation, the wire length is converted from 120 mm to 0.120 m and substituted into 0.36 = B x 4.0 x 0.120 to give B = 0.75 T. The Fleming's left-hand rule labels are magnetic field, current, and force.

AO /

Question Answers Extra information Mark

Spec. Ref.

04.1 at the poles 1 AO1

6.7.1.2

04.2 the distance between the field 1 AO1

lines varies 6.7.1.2

04.3 electromagnet is easy to allow electromagnet can be 1 AO1

demagnetise switched off 6.7.2.1

so easy to remove separated 1

metal

allow electromagnet is

(generally) stronger than a

permanent magnet for 1 mark if

no other marks are awarded

04.4 cobalt 1 AO1

6.7.1.2

nickel 1

04.5 increases the current in the coil allow increase potential 1 AO1

of the electromagnet difference across the coil

1 AO3

bring the electromagnet closer

to the pieces of iron and steel 6.7.2.1

04.6 L = 0.120 m 1 AO2

6.7.2.2

0.36 = B × 4.0 × 0.120 allow a correct substitution of an 1

incorrectly / not converted value

of L

0.36 allow a correct rearrangement 1

B =

(4.0 × 0.120) using an incorrectly / not

converted value of L

allow a correct calculation using 1

B = 0.75

an incorrectly / not converted

value of L

T

04.7 2 AO1

6.7.2.2

allow 1 mark for 1 or 2 correct

Total 15

How to answer it

Magnetism, Electromagnets and Motor Force

What this question tests
You need to read magnetic field patterns, explain why electromagnets are useful, recall which metals are magnetic, and use the equation F = BIL to calculate magnetic flux density. You also need to know Fleming’s left-hand rule and label the three directions correctly.
Overall focus: magnetism in simple contexts

This question is a mix of recall, explanation, and one calculation. The marks are straightforward if you use the key physics words: poles, field lines, current, force, and magnetic flux density.

Part (a) 04.1 — Where is the magnetic field strongest?

✅ Correct answer

At the poles.

1 mark: the field is strongest where the field lines are closest together, which is at the ends of the magnet.

💡 Key knowledge

  • Magnetic field lines are closest together where the field is strongest.
  • The ends of a magnet are called the poles.

🧠 Exam technique

Use the exact science term poles. Saying “near the magnet” is too vague for full credit.

❌ Common errors

  • Saying “in the middle” — that is where the field is weaker.
  • Describing “where the lines go” without stating the poles.

Part (b) 04.2 — How does Figure 4 show the field strength is not the same everywhere?

✅ Correct answer

The distance between the field lines varies.

1 mark: closer lines mean a stronger field; wider spacing means a weaker field.

💡 Key knowledge

  • Magnetic field strength is shown by the spacing of field lines.
  • Closer field lines = stronger magnetic field.

🧠 Exam technique

The mark scheme wants the idea of variation in spacing. If you write “the lines are closer near the poles,” that also scores.

❌ Common errors

  • Just saying “there are more lines” without mentioning spacing.
  • Saying “the lines curve” — curvature is not the key point.

Part (c) 04.3 — Why use an electromagnet instead of a permanent magnet?

✅ Correct answers

  • An electromagnet can be switched off, so the separated metal can be removed easily.
  • An electromagnet can be demagnetised when needed.
  • It can also be stronger than a permanent magnet.
2 marks: one mark for a reason linked to switching off/demagnetising, and one mark for removing the metal easily or being stronger.

💡 Key knowledge

  • Electromagnets only work when current flows.
  • That makes them useful in scrapyards and metal sorting.

🧠 Exam technique

To score both marks, give two separate points. A good pair is: “It can be switched off, so the metal is released” and “it can be stronger”.

❌ Common errors

  • Only saying “it is better” — too vague.
  • Writing “because it is magnetic” — both types are magnetic.

Part (d) 04.4 — Name two other metals attracted to the electromagnet

✅ Correct answers

  • cobalt
  • nickel
1 mark each. Both are magnetic metals.

💡 Key knowledge

  • The main magnetic metals at GCSE are iron, cobalt and nickel.
  • Steel is attracted because it contains iron.

🧠 Exam technique

Learn the trio: iron, cobalt, nickel. If the question says “other metals”, do not repeat iron or steel.

❌ Common errors

  • Giving aluminium, copper or gold — these are not attracted.
  • Writing “steel” as a metal here; the mark scheme wants the named metals cobalt and nickel.

Part (e) 04.5 — How could the force of the electromagnet be increased?

✅ Correct answers

  • Increase the current in the coil of the electromagnet.
  • Bring the electromagnet closer to the pieces of iron and steel.
  • Allowable alternative: increase the potential difference across the coil.
2 marks: one for each different way of increasing the force.

💡 Key knowledge

  • Electromagnet strength depends on the current.
  • Magnetic force gets bigger when the magnet is closer to the object.

🧠 Exam technique

Give two different methods. “Make it stronger” is not enough unless you say how.

❌ Common errors

  • Saying “use a bigger magnet” when the design cannot be changed.
  • Repeating the same idea in different words.

Part (f) 04.6 — Calculate the magnetic flux density

📐 Calculations: step-by-step

  1. Write the equation: F = BIL
  2. Convert the length: 120 mm = 0.120 m
  3. Substitute the values: 0.36 = B × 4.0 × 0.120
  4. Rearrange: B = 0.36 ÷ (4.0 × 0.120)
  5. Calculate: B = 0.36 ÷ 0.48 = 0.75
  6. State the unit: T (tesla)

Final answer: 0.75 T

5 marks: setting up the equation, converting mm to m, substitution, rearrangement, correct final answer and unit.

💡 Key knowledge

  • F = force in newtons (N)
  • B = magnetic flux density in tesla (T)
  • I = current in amperes (A)
  • L = length in metres (m)

🧠 Exam technique

  • Always convert mm to m: 120 mm = 0.120 m.
  • Include the unit T for tesla.
  • Use all the numbers given in the question.

❌ Common calculation traps

  • Using 120 instead of 0.120 .
  • Forgetting the unit.
  • Mixing up the rearrangement and writing B = F × I × L .
  • Rounding too early.

Part (g) 04.7 — Fleming’s left-hand rule

✅ Correct labels

  • Direction of magnetic field
  • Direction of current
  • Direction of force
2 marks: the three fingers must be labelled correctly. One mark can be earned for 1 or 2 correct labels.

💡 Key knowledge

  • Fleming’s left-hand rule links magnetic field, current, and force.
  • First finger = field, second finger = current, thumb = force.

🧠 Exam technique

Do not mix up current and force. The labels need to match the hand diagram, not just the words.

❌ Common errors

  • Writing “power” instead of force.
  • Confusing magnetic field with current direction.
  • Using the right-hand rule instead of the left-hand rule.

Quick revision summary

💡 Key facts to remember

  • Magnetic field is strongest at the poles.
  • Field strength is shown by field line spacing.
  • Electromagnets can be switched off.
  • Magnetic metals: iron, cobalt, nickel.
  • Force on a wire in a magnetic field uses F = BIL .
  • Fleming’s left-hand rule gives field, current, force.

🧠 How to pick up full marks

  • Use the exact physics term from the mark scheme.
  • For 2-mark explain questions, give two distinct points.
  • In calculations, show conversion, substitution, rearrangement, answer, and unit.

Topics

Physics · P7: Magnetism and Electromagnetism

Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Physics Paper 2 (Higher), 2021. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.