OCR GCSE Physics A: Magnets, magnetic fields and electromagnets (J249) – 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 P4.1, Magnets and magnetic fields (P4.1a to P4.1g), from the OCR GCSE (9-1) Gateway Science Physics A (J249) specification, Version 5.0 (July 2026). All of them are suitable for both tiers. Read the study guide and revision notes first if you need to. Course pages: OCR GCSE Physics hub and the checklist.

Questions

1. Two bar magnets are placed on a bench.

(a) Say what happens if two north poles are brought together. [1] (b) Say what happens if a north pole and a south pole are brought together. [1]

2. A steel paper clip hangs from the north pole of a bar magnet. Explain, using the idea of induced magnetism, why the clip does not fall. [3]

3. A student tests three rods, P, Q and R, using the north pole of a bar magnet.

Rod	End 1	End 2
P	attracted	attracted
Q	repelled	attracted
R	no force	no force

(a) Identify the rod that is a permanent magnet and give the reason. [2] (b) State what rod P could be made of, if it is not a magnet. [1] (c) Suggest what rod R could be made of. [1]

4. Describe how you would plot the magnetic field around a bar magnet using a plotting compass. [4]

5. A diagram shows the field lines around a bar magnet. Near one pole the lines are 0.5 cm apart. At point B, further away, they are 1.5 cm apart.

(a) State which position has the stronger field and explain how you know. [2] (b) Calculate how many times further apart the lines are at B than near the pole. [1]

6. A dipping compass has its needle free to turn in a vertical plane. At location X the needle is 70 degrees below the horizontal. At location Y it is 5 degrees below the horizontal.

(a) State which location is nearer a magnetic pole of the Earth. [1] (b) Explain how the behaviour of a dipping compass is related to evidence that the core of the Earth must be magnetic. [3]

7. A long straight vertical wire passes through a horizontal card. Small plotting compasses are placed on the card around the wire.

(a) Describe the pattern of the magnetic field when a large direct current flows in the wire. [2] (b) State what happens to the compass needles when the current is reversed. [1]

8. Plotting compasses are placed on a card at different distances from a current-carrying wire. The Earth’s field is the same at each. The table shows how far each needle turns from its original direction.

Distance from wire (cm)	3	6	9	12
Turn of needle (degrees)	55	30	17	9

(a) Describe the trend shown. [2] (b) State what the trend shows about the field strength. [1] (c) State what would happen to the turn at 6 cm if the current were increased. [1]

9. A student winds a wire into a solenoid and connects it to a power supply.

(a) State which magnet the shape of the field outside a solenoid resembles. [1] (b) Explain why coiling the wire makes the field stronger than that of a straight wire. [2] (c) State two other changes that would strengthen the field. [2]

10. A student investigates an electromagnet at a constant current of 1.0 A. The number of paper clips it can pick up is recorded.

Number of turns	25	50	75	100
Clips lifted	6	12	19	23

(a) Describe the pattern in the results. [2] (b) Calculate the percentage increase in clips lifted from 25 turns to 100 turns. [2] (c) State two variables that must be controlled. [2]

11. A scrapyard crane uses a large electromagnet to lift steel scrap and drop it somewhere else. Explain how the electromagnet works, why its core is soft iron and how it could be made to lift a heavier load. [6]

12. A solenoid has 240 turns spread evenly over 12 cm. It carries a current of 0.8 A.

(a) Calculate the number of turns per centimetre. [1] (b) The coil is compressed to 8 cm long with the same turns. Calculate the new turns per centimetre and the percentage increase. [2] (c) The current is then raised from 0.8 A to 1.4 A. Calculate the percentage increase in current. [1] (d) State the effect of both changes on the strength of the magnetic field in the solenoid. [2]

Answers

1. (a) The two magnets repel. [1] (b) They attract. [1] Examiner insight: Writing only “they are pulled together” for like poles loses the mark because the force direction is the answer, so name attract or repel.

2. The magnet’s field makes the clip an induced magnet [1]. The end of the clip nearest the north pole becomes a south pole [1]. Opposite poles attract, so the force of attraction holds up the clip against its weight [1]. [3] Examiner insight: The explanation needs the idea of an induced pole at the end nearest the magnet, not just the statement that steel is magnetic.

3. (a) Rod Q [1]. Only a magnet can repel the north pole, since an induced magnet is always attracted [1]. [2] (b) Iron or steel (or cobalt or nickel) that is not magnetised [1]. [1] (c) A non-magnetic material such as copper, aluminium or plastic [1]. [1] Examiner insight: Attraction alone proves nothing, so an answer naming P as the magnet because it is attracted scores nothing for the reason.

4. Place the bar magnet on paper and put a plotting compass near one pole [1]. Mark the positions of both ends of the needle with pencil dots [1]. Move the compass so that its tail end is on the previous dot, and mark the new head end, repeating until the other pole is reached [1]. Join the dots into a smooth line and add an arrow showing the direction the north end of the needle points (towards the south pole); repeat from other starting points [1]. [4] Examiner insight: A method that omits the step of moving the compass along the line is incomplete, and joining the dots without an arrow leaves direction unstated.

5. (a) The field is stronger near the pole [1]. The lines are closer together there, and closer lines mean a stronger field [1]. [2] (b) 1.5 ÷ 0.5 = 3 times further apart [1]. [1] Examiner insight: “The lines are bigger” is not an explanation; link the spacing to the strength, and do not suggest that three times the spacing means exactly one third of the strength.

6. (a) Location X [1]. [1] (b) A compass needle is itself a small magnet, so it settles along whatever field surrounds it [1]. The needle is almost vertical near the poles and nearly horizontal near the equator, which matches the field of a bar magnet [1]. A magnetic field is produced by a magnet or a current, so the Earth’s core must be magnetic [1]. [3] Examiner insight: Saying “the compass points north so there is a magnet inside” is too vague; reference the dip pattern and the idea that the compass aligns with the field.

7. (a) The field forms concentric circles [1] centred on the wire, in planes at right angles to it [1]. [2] (b) Every needle turns through 180 degrees, so the field direction reverses [1]. [1] Examiner insight: Straight lines or lines pointing outwards from the wire are the usual wrong answers; say circles, not just “round”.

8. (a) As the distance from the wire increases, the turn of the needle decreases [1], from 55 degrees at 3 cm to 9 degrees at 12 cm [1]. [2] (b) The field is weaker the further it is from the wire [1]. [1] (c) The needle would turn through a larger angle [1]. [1] Examiner insight: Quote values from the table with units, and describe both the direction of the trend and the data.

9. (a) A bar magnet [1]. [1] (b) Each loop of wire produces its own field [1]. Inside the coil these fields point in the same direction and add together [1]. [2] (c) Any two of: increase the current, add more turns, put the turns closer together, add an iron core [2]. [2] Examiner insight: “Make the solenoid bigger” does not gain a mark because it can mean longer, which weakens the field per turn.

10. (a) More turns means more clips lifted [1]. The number rises from 6 at 25 turns to 23 at 100 turns, roughly in proportion [1]. [2] (b) (23 − 6) ÷ 6 × 100 [1] = 283% (3 s.f.) [1]. [2] (c) Any two of: the current, the core material, the length of the coil, the size and type of paper clips [2]. [2] Examiner insight: Percentage change divides by the original value, so dividing by 23 gives a wrong answer even with correct subtraction.

11. Current in the coil produces a magnetic field [1]. The iron core becomes an induced magnet, adding to the field [1]. The steel scrap is attracted because it also becomes an induced magnet [1]. Soft iron is used because it stops being magnetic soon after the current stops [1], so the scrap drops [1]. Increasing the current or adding more turns gives a stronger field and can lift a heavier load [1]. [6] Examiner insight: A long answer needs separate points for how it works, why soft iron and how to improve it; repeating “it is magnetic” gains little.

12. (a) 240 ÷ 12 = 20 turns per cm [1]. [1] (b) 240 ÷ 8 = 30 turns per cm [1], so the increase is (30 − 20) ÷ 20 × 100 = 50% [1]. [2] (c) (1.4 − 0.8) ÷ 0.8 × 100 = 75% [1]. [1] (d) Both changes make the field stronger [1], because more turns per centimetre and a larger current each increase the field in the solenoid [1]. [2] Examiner insight: Show the subtraction and division so that the examiner can follow each step, and state the direction of the effect, not just “it changes”.

Where marks are usually lost

• Drawing or describing field lines that cross, or have no arrows.
• Saying attraction proves a rod is a magnet.
• Forgetting that an induced magnet is always attracted.
• Writing that the field lines run from south to north outside the magnet.
• Describing the field around a wire as straight lines.
• Quoting no figures from a table when asked to describe a trend.
• Dividing a percentage change by the new value instead of the original.
• Giving “bigger” or “stronger” with no variable named when asked how to change an electromagnet.
• Writing about the compass without saying that it is a small magnet.

Next steps

• Revision notes
• Study guide
• OCR GCSE Physics hub
• Checklist
• All free 10-minute diagnostics
• Book a free trial class

Official syllabus

OCR GCSE (9-1) Gateway Science Physics A (J249), specification Version 5.0 (July 2026), first assessment 2018, published by OCR. This page covers topic P4.1.