This set mixes the five skills from magnetism and fields: field patterns, induced magnetism, the force on a wire, permanent and temporary magnets, and reading magnetic tests. All questions and data are original and invented for practice. They are not from any past paper.
Work each question on paper first, sketch where a question asks for a pattern, then open the worked answer. Keep a note of the ones you miss, and the mistake log and retest queue can help you sort them by error type.
Questions, easy to harder
Q1. A north pole is on the left and a south pole is on the right, close together. Which way does the field point in the gap between them?
Show answer
Left to right. Field lines leave the north pole and enter the south pole.
Q2. Two identical bar magnets face each other with their north poles nearest. Describe the field pattern between them, and state the field at the exact midpoint.
Show answer
Lines from each north pole curve away from the other magnet, so the lines do not cross the gap. At the midpoint the two fields have equal size and opposite direction, so the field is zero (a neutral point).
Q3. The south pole of a magnet is brought near an unmagnetised iron nail. The nail is attracted. Explain why, stating the pole at the nearest end of the nail.
Show answer
The magnet’s field induces magnetism in the iron. The end nearest the south pole becomes a north pole, the opposite type. Unlike poles attract, so the nail is pulled towards the magnet.
Q4. A solenoid is connected to a cell. Looking at its left end, the current flows anticlockwise. Which pole is at the left end?
Show answer
North. The end where the current looks anticlockwise is the north pole. Check with the right-hand grip rule: fingers curl anticlockwise, thumb points towards you, which is the north end.
Q5. A straight vertical wire carries current out of the page towards you. In which direction do the field lines circle around it?
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Anticlockwise. Thumb points out of the page along the current, and the fingers curl anticlockwise. Lines are circles that get further apart with distance, since the field gets weaker.
Q6. Three bars are each brought to the north pole of a known magnet. Bar X is repelled at one end. Bar Y is attracted at both ends. Bar Z shows no effect at either end. Classify each bar.
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X is a magnet (repulsion is the reliable test). Y is an unmagnetised magnetic material such as iron. Z is not magnetic, for example plastic or copper.
Q7. A uniform field points to the right. A wire carries current into the page. In which direction is the force on the wire?
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First finger (field) points right, second finger (conventional current) points into the page, and the thumb points downwards. The force is down the page.
Q8. The field points up the page and the current flows to the right. Which way is the force?
Show answer
Turn the left hand so the first finger points up and the second finger points right. The thumb then points out of the page, towards you. Quick check: reversing the current would send the force into the page.
Q9. A wire in a uniform field at right angles carries 2.0 A, and the force is 0.030 N. (Invented data.) (a) What is the force at 3.0 A? (b) What is the force at 2.0 A if the field is halved? (c) Describe the force if both current and field are reversed.
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(a) Force is proportional to current: 0.030 ÷ 2.0 = 0.015 N per A, and 0.015 × 3.0 = 0.045 N. (b) Half the field gives half the force: 0.015 N. (c) Reversing both leaves the direction unchanged: same size and direction, 0.030 N.
Q10. A crane must lift scrap iron and release it when switched off. Explain why the core of its electromagnet is soft iron rather than steel.
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Soft iron is magnetised strongly while the current flows and loses its magnetism when the current stops, so the load drops. A steel core would keep some magnetism, and the load might not be released.
Q11. A student tests two electromagnets that have the same coil, one with an iron core and one with a steel core. The table shows paper clips held. (Invented data.)
| Core | Current (A) | Clips held, current on | Clips held, current off |
|---|---|---|---|
| Iron | 1.0 | 5 | 0 |
| Iron | 2.0 | 10 | 0 |
| Steel | 1.0 | 4 | 3 |
(a) What does the iron core data show about current and strength? (b) What does the steel result show?
Show answer
(a) Doubling the current from 1.0 A to 2.0 A doubled the clips, 5 to 10, so in this data the strength increases with current, and is roughly proportional. (b) The steel core still held 3 clips with the current off, so it keeps some magnetism, unlike iron, which held 0. Steel is a poor choice where the magnetism must switch off.
If you got these wrong
| What went wrong | Questions | Go to |
|---|---|---|
| Arrow direction, neutral point or solenoid poles | Q1, Q2, Q4, Q5 | Sketch a field pattern with direction |
| Wrong induced pole, or wrong reasoning for attraction | Q3 | Explain induced magnetism |
| Hand rule direction or proportional reasoning | Q7, Q8, Q9 | Use a field-current-force relationship |
| Iron against steel, or electromagnet choices | Q10, Q11 | Compare permanent and temporary magnetic behaviour |
| Calling every attracted bar a magnet | Q6 | Interpret a magnetic test |
Go back to the module page if you missed questions in several rows.
Patterns across several questions are easier to see with someone else looking at your working. Our teachers can do this in online one-to-one Physics tuition.