AQA GCSE Physics Physics Paper 2 (Foundation), November 2020: Question 5

11 marks · Standard Demand difficulty · Short Answer

Analyze magnetic interactions, plot magnetic field patterns using a compass, order sequence for an electromagnetic lock, and calculate the elastic potential energy of a spring.

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Question text

05 A student placed a magnet on top of a plastic support in a bowl of water. This magnet

was fixed in position and above the surface of the water.

The student put a second magnet into a piece of cork so that the magnet floated on

the water. Only the north pole of the floating magnet was above the surface of the

water.

Figure 6 shows the arrangement of the magnets.

Figure 6

05.1 The floating magnet was placed near to the north pole of the fixed magnet. The

floating magnet then moved along the path shown in Figure 6.

Explain why.

[2 marks]

05.2 The student replaced the floating magnet with a piece of iron.

What happened to the piece of iron?

*19* [1 mark]

05.3 Describe how to use a compass to plot the magnetic field pattern around a bar

magnet.

Use Figure 7 to help you.

[4 marks]

Figure 7

Figure 8 shows a diagram of an electromagnetic lock used to secure a door.

Figure 8

05.4 Figure 9 shows an incomplete sequence of how the door unlocks.

Figure 9

The switch The door

is closed. unlocks.

Write one letter in each box to show the correct sequence.

[2 marks]

A The iron bolt moves.

B A magnetic field is created around the solenoid.

C There is a current in the circuit.

05.5 The electromagnetic lock contains a spring.

When the door is unlocked the extension of the spring is 0.040 m.

spring constant = 200 N/m

Calculate the elastic potential energy of the spring when the door is unlocked.

Use the equation:

elastic potential energy = 0.5 × spring constant × (extension)2

[2 marks]

Elastic potential energy = J

Mark scheme

Show the mark scheme

Question 5

AO /

Question Answers Extra information Mark

Spec. Ref.

05.1 (the north pole of the floating 1 AO3

magnet is) repelled from the 4.7.1.1

north pole (of the fixed magnet) 4.7.1.2

and attracted to the south pole 1

(of the fixed magnet)

allow following a magnetic field

line for 1 mark if no other marks

scored

05.2 it was attracted (to the fixed allow it sticks / joins to the 1 AO1

magnet) (fixed) magnet 4.7.1.2

allow it becomes an induced

magnet

allow it becomes magnetised

Level 2: The design/plan would lead to the production of a valid AO1

05.3 3–4

outcome. All key steps are identified and logically sequenced. 4.7.1.2

Level 1: The design/plan would not lead to a valid outcome. Some

1–2

relevant steps are identified, but links are not made clear.

No relevant content 0

Indicative content:

• mark where the compass points on the paper

• move the compass to the marked point

• repeat until you go back to the magnet

• join up the points

• add an arrow pointing from the north pole to the south pole

• repeat for positions (above and below the bar magnet)

05.4 C B A 2 AO2

allow 1 mark for one letter in the 4.7.2.1

correct box

05.5 E = 0.5 x 200 x 0.0402 1 AO2

4.5.3

Ee = 0.16 (J) 1

Total 11

How to answer it

GCSE Physics Study Guide: Magnets & Electromagnetism

What this question tests

This question assesses your understanding of permanent magnetism, magnetic forces (repulsion and attraction), induced magnetism, practical methods for plotting magnetic field lines, the step-by-step operation of an electromagnetic lock, and applying the elastic potential energy equation to a spring.

Part 05.1 [2 marks]

Explaining Magnetic Motion

✅ Correct Answer

The north pole of the floating magnet is repelled from the north pole of the fixed magnet, and attracted to the south pole of the fixed magnet.

Mark breakdown: 1 mark for stating repulsion from the north pole, 1 mark for attraction to the south pole. (Allow 1 mark for following a magnetic field line if no other marks are scored).

💡 Key Knowledge

Like magnetic poles repel (North-North / South-South).
Unlike magnetic poles attract (North-South).
Magnetic forces are non-contact forces.

Part 05.2 [1 mark]

Induced Magnetism in Iron

✅ Correct Answer

It was attracted (to the fixed magnet).

Mark breakdown: 1 mark for stating it was attracted, or that it sticks/joins to the magnet, becomes magnetized, or becomes an induced magnet.

❌ Common Errors

Students sometimes incorrectly state that iron will be repelled. Remember that unmagnetized iron is always attracted to a magnet because the magnet induces an opposite pole closest to it.

Part 05.3 [4 marks]

Plotting a Magnetic Field Pattern

✅ Correct Answer (Level 2: 3–4 marks)

1. Place the compass on the paper near the bar magnet.
2. Mark where the needle (or pointer) points on the paper.
3. Move the compass so that its tail is at the newly marked point, then mark the new position of the tip.
4. Repeat this process until you reach the other pole or loop back around.
5. Join up the points with a smooth curve and add arrows pointing from North to South.
6. Repeat for multiple positions around the bar magnet.

Mark breakdown: Level 2 (3–4 marks) requires a valid, logically sequenced plan identifying all key steps. Level 1 (1–2 marks) covers partial steps without clear links.

🧠 Exam Technique

When describing practical methods in physics, write clear numbered steps. Always explicitly mention the physical action (e.g., "mark the dot", "move the compass", "join the dots") and don't forget to include adding directional arrows from North to South.

Part 05.4 [2 marks]

Sequence of an Electromagnetic Lock

✅ Correct Answer

C → B → A

Full sequence: The switch is closed → C (There is a current in the circuit) → B (A magnetic field is created around the solenoid) → A (The iron bolt moves) → The door unlocks.

Mark breakdown: 2 marks for all three letters in the correct boxes. (1 mark if only one letter is correctly placed).

💡 Key Knowledge

An electromagnet works by passing an electrical current through a wire coil (solenoid), which creates a magnetic field. This magnetic field exerts a force on magnetic materials (like the iron bolt), pulling it out of the door frame.

Part 05.5 [2 marks]

Calculation of Elastic Potential Energy

📐 Step-by-Step Calculation

Equation: Elastic potential energy ( E_e ) = 0.5 × spring constant × (extension)²

Step 1: Identify your values from the question
Spring constant ( k ) = 200 N/m
Extension ( e ) = 0.040 m

Step 2: Substitute values into the equation
E_e = 0.5 × 200 × (0.040)²

Step 3: Evaluate carefully
(0.040)² = 0.0016
0.5 × 200 = 100
E_e = 100 × 0.0016 = 0.16 J

Final Answer: 0.16 J

Mark breakdown: 1 mark for correct substitution into the equation, 1 mark for the correct final answer with units.

❌ Common Calculation Traps

Forgetting to square the extension: Students often calculate 0.5 × 200 × 0.040 instead of squaring 0.040 .
Unit conversion errors: Always check if extensions are given in centimeters (cm). If they are, you must convert them into meters (m) by dividing by 100 before squaring!

Topics

Physics · P5: Forces · P7: Magnetism and Electromagnetism

Question and mark scheme from the AQA GCSE Physics examination, Physics Paper 2 (Foundation), November 2020. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.