OxfordAQA International GCSE Physics: Magnets, magnetic fields and electromagnets (9203) – 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 follow the OxfordAQA International GCSE Physics (9203) specification, for exams May/June 2018 onwards, section 3.5.2 (Magnetism and electromagnetism), including the required practical on electromagnets.

Links: study guide, revision notes, course hub, printable checklist and the 10-minute diagnostics.

Questions

1. The north pole of bar magnet A is held close to the south pole of bar magnet B. State what happens and name the type of force. [2]

2. (a) From copper, nickel, aluminium, cobalt and zinc, name the two magnetic materials. [2] (b) A student has a metal bar that is attracted to a magnet. State the test that shows whether the bar is itself a magnet. [1]

3. Two bar magnets lie in line with their north poles facing, 4 cm apart. Describe the magnetic field pattern in the gap. [3]

4. Explain how a bar magnet picks up an unmagnetised steel paper clip. [4]

5. (a) Explain why the needle of a plotting compass settles pointing north. [2] (b) A hiker’s compass gives a wrong reading when held next to a steel flask. Explain why. [2]

6. A long straight wire carries a current. (a) Describe what the magnetic field lines around the wire look like. [2] (b) State one way of making the field stronger at a point, and state the effect of reversing the current. [2]

7. A plotting compass is placed at different distances from a straight wire carrying a steady current. The needle turns through 48 degrees at 3 cm, 30 degrees at 6 cm and 21 degrees at 9 cm. (a) State the trend and explain it. [2] (b) Calculate the percentage decrease in the turn from 3 cm to 9 cm. Give your answer to 3 significant figures. [2]

8. A wire is wound into a solenoid. (a) Explain why a solenoid gives a stronger field than a single straight wire carrying the same current. [2] (b) Describe the field inside the solenoid. [1] (c) State how the field outside compares with that of a bar magnet, and what happens to it when the current is reversed. [2]

9. A scrapyard crane uses an electromagnet with a soft iron core to move steel. Explain why an iron core is used, and how the load is released. [4]

10. A student uses a coil on an iron nail and a constant current. She counts the paper clips lifted in three trials for four numbers of turns.

Turns	Trial 1	Trial 2	Trial 3
15	3	4	3
30	6	7	7
45	10	9	10
60	13	13	14

(a) Calculate the mean clips lifted for 15 turns and for 60 turns. Give each to 3 significant figures. [2] (b) State the conclusion the data support, using the ratio of the two means. [2] (c) Give two variables the student must keep the same. [2]

11. Plan and analyse an investigation into how the current affects the strength of an electromagnet. (a) Describe a method, naming the apparatus, the variable you change, the variable you measure and how you improve reliability. [5] (b) Mean clips lifted for 0.4, 0.8, 1.2 and 1.6 A were 2.0, 4.3, 6.1 and 8.0. Calculate the percentage increase in clips from 0.8 A to 1.6 A, and say what 8.0 compared with 2.0 shows. [3]

Answers

1. The magnets attract [1]. It is a non-contact force [1]. [2] Examiner insight: Naming the poles as unlike, and the force as non-contact, are separate points, so give both.

2. (a) Nickel [1] and cobalt [1]. [2] (b) See whether it repels a known pole of a magnet [1]. [1] Examiner insight: “It is attracted” does not answer part (b), since iron is attracted too. Name repulsion.

3. Lines leave each north pole and curve away from the other magnet [1]. The lines do not cross, and arrows point away from each north pole [1]. There is a point midway where the field is zero [1]. [3] Examiner insight: A sketch is easier to credit when arrows are shown and no lines cross. In words, name the neutral point.

4. The magnet’s field magnetises the clip, so it becomes an induced magnet [1]. The end nearest the magnet’s pole becomes the opposite pole [1]. Opposite poles attract [1]. Induced magnetism always gives attraction, so the clip is pulled to the magnet whichever pole is used [1]. [4] Examiner insight: The step that the nearer end takes the opposite pole is the one most often left out. Write it out.

5. (a) The needle is a small magnet that can turn freely [1]. It lines up with the Earth’s magnetic field, so its north-seeking end points towards the Earth’s north [1]. [2] (b) The steel flask is made of a magnetic material, which becomes an induced magnet [1]. Its field acts on the needle and changes the direction it points [1]. [2] Examiner insight: Say that a second field acts on the needle. “The flask interferes” is too vague to gain credit.

6. (a) Concentric circles [1] in a plane perpendicular to the wire, centred on the wire [1]. [2] (b) Increase the current (or move closer to the wire) [1]. Reversing the current reverses the field direction [1]. [2] Examiner insight: “Circles” alone is incomplete. Give the orientation to the wire, or the centre.

7. (a) The turn decreases as the distance increases [1] because the field is weaker further from the wire [1]. [2] (b) (48 − 21) / 48 × 100 [1] = 56.3% [1]. [2] Examiner insight: Write the unrounded working first. Then give the answer to the 3 significant figures requested.

8. (a) Each turn produces its own circular field [1]. Inside the coil the fields add together in the same direction [1]. [2] (b) The field is strong and uniform [1]. [1] (c) The field outside has a similar shape to that of a bar magnet [1]. Reversing the current swaps the poles [1]. [2] Examiner insight: Compare the solenoid with a straight wire at the same current. A bare statement that it is “stronger” is unlikely to be enough.

9. Iron becomes a strong induced magnet in the coil’s field, so the core increases the field strength [1], and it can lift more steel [1]. When the current is switched off, the iron loses most or all of its magnetism quickly [1]. The load is no longer held and drops [1]. [4] Examiner insight: Two ideas are needed: a stronger magnet when on and loss of magnetism when off. Do not say the current “stops attracting”.

10. (a) 15 turns: (3 + 4 + 3) / 3 = 3.33 clips [1]. 60 turns: (13 + 13 + 14) / 3 = 13.3 clips [1]. [2] (b) 13.33 / 3.33 = 4.0, the same as 60 / 15 [1], so more turns give a stronger electromagnet, with strength close to proportional to the number of turns [1]. [2] (c) Any two: the current, the core, the nail and clips [1] [1]. [2] Examiner insight: Use the data in the conclusion. A conclusion with no figures from the table is hard to credit in full.

11. (a) Wind insulated wire on an iron nail and connect it to a dc supply, ammeter, variable resistor and switch [1]. Change the current with the variable resistor and read it on the ammeter [1]. Measure the clips lifted [1]. Keep the turns, the core and the clips the same [1]. Repeat each setting at least three times and take a mean [1]. [5] (b) (8.0 − 4.3) / 4.3 × 100 [1] = 86.0% [1]. Quadrupling the current from 0.4 A to 1.6 A gives four times the clips (8.0 / 2.0 = 4.0), so the strength is proportional to the current over this range [1]. [3] Examiner insight: A good plan names the apparatus, what changes, what is measured and what stays the same. State all four.

Where marks are usually lost

• Writing “attracts metal” and not naming iron, steel, cobalt or nickel.
• Describing attraction without saying the poles are unlike.
• Missing arrows on field lines, or drawing lines that cross.
• Claiming that induced magnetism can give repulsion.
• Giving the wire’s field as “around the wire” instead of concentric circles perpendicular to it.
• Writing “stronger” with no comparison.
• Giving “more power” in place of a larger current or more turns.
• Taking one reading in an investigation instead of repeating it and averaging.
• Forgetting to control a variable.

Next steps

• Re-read the study guide and the revision notes.
• Tick off the topic on the printable checklist and return to the course hub.
• Take all free 10-minute diagnostics at diagnostics.
• Book a free trial class at trial.

Official syllabus

OxfordAQA International GCSE Physics (9203) specification, for exams May/June 2018 onwards, published by OxfordAQA. This page covers section 3.5.2.