AQA GCSE Combined Science: Trilogy Physics Paper 2 (Foundation), November 2020: Question 6

✅ Correct Answer

• Iron and steel will be attracted to the magnet. [1 mark]
• Aluminium, copper, and tin will not be attracted. [1 mark]

💡 Key Knowledge

• Only four common magnetic elements exist: iron, nickel, cobalt (plus the alloy steel, which contains iron).
• All other metals (like copper, aluminium, gold, and tin) are non-magnetic and will not experience a force from a permanent magnet.

🧠 Exam Technique

The command word is "Describe what happened". State clearly what is observed for every sample shown. Dividing the five metals into "attracted" and "not attracted" covers all bases completely.

❌ Common Errors

• Assuming all shiny metals are magnetic (e.g. thinking aluminium or copper sticks to magnets).
• Writing that non-magnetic metals are "repelled" — non-magnetic metals experience no force at all.

✅ Correct Answer

• The paper clip would still be attracted to the magnet. [1 mark]
• Because of induced magnetism (or the paper clip becomes an induced magnet / temporary magnet). [1 mark]

💡 Key Knowledge

• Permanent magnet: Produces its own magnetic field and has fixed poles.
• Induced magnet: A material that only becomes magnetic when placed inside an external magnetic field.
• Induced magnetism always causes a force of attraction, regardless of whether it approaches the North or South pole!

🧠 Exam Technique

Two marks mean two parts to your answer: Observation (what happens) + Explanation (scientific reason why). Structure your answer as: "[Observation] because [scientific term]."

❌ Common Errors

• Thinking the paper clip will be repelled by the South pole because it was previously near the North pole. Once removed, an unmagnetised paperclip loses its induced magnetism quickly.
• Confusing permanent magnets (which can repel) with induced magnets (which only attract).

✅ Correct Answer

weight = mass × gravitational field strength

or

W = m × g (or W = mg ) [1 mark]

💡 Key Knowledge

• Weight (W): Force measured in newtons (N).
• Mass (m): Amount of matter measured in kilograms (kg).
• Gravitational field strength (g): Measured in N/kg (approx. 9.8 N/kg on Earth).

❌ Common Errors

• Writing "gravity" instead of "gravitational field strength" — the mark scheme explicitly states: do not accept gravity.
• Mixing up mass and weight (e.g. writing m = W × g ).

📐 Step-by-Step Calculation

1. Convert mass to standard SI units (kilograms):
   Total mass = 20 × 1.0 g = 20 g
   20 g ÷ 1000 = 0.020 kg
   (Alternatively: mass of 1 clip = 1.0 ÷ 1000 = 0.0010 kg ) [1 mark]
2. Substitute into formula:
   W = m × g
   Total weight = 0.020 kg × 9.8 N/kg
   (Or weight of 1 clip = 0.0010 × 9.8 = 0.0098 N ) [1 mark]
3. Calculate final force:
   Total force = 0.196 N
   (Or 0.0098 N × 20 = 0.196 N ) [1 mark]

🧠 Exam Technique: Upward Force = Downward Weight

For the magnet to support the paperclips without them falling, the upward magnetic attraction force must balance the downward force of gravity (total weight).

Therefore:

Maximum Force = Total Weight

❌ Calculation Traps

• Forgetting unit conversion: Multiplying 20 × 9.8 = 196 N forgets that mass must be in kg, not grams. (This yields an error carried forward penalty).
• Calculating for only 1 clip: Finding 0.0098 N and forgetting to multiply by 20 clips.