Cutting a bar magnet does not isolate one pole; each piece becomes a smaller magnet with its own north and south poles. This guide is for a Primary 6 learner who can often complete the easy part of a question but loses accuracy when a familiar word, number relationship, observation or piece of evidence is used too broadly. The difficulty is not usually a lack of effort. It is a control problem: the mind recognises something useful and stops checking before the task contract has been fully satisfied.
The repair is to separate three moves. First, identify exactly what the information establishes. Second, identify what it does not establish. Third, connect only the supported conclusion to the wording of the question. That three-part habit is small enough to use under examination pressure and strong enough to prevent many confident but unsupported answers.
This article develops that habit through mechanism-led explanation, worked examples, misconception repair, independent practice, delayed transfer and examination control. It belongs to the complete Learner’s Guide volume directory and continues the earlier PSLE Learning Guide foundation. The current official subject documents can be reached through SEAB’s 2026 PSLE formats page; always use the document for the year in which you will sit the examination.
The learner problem
A bar magnet is often drawn with N at one end and S at the other. A learner may therefore imagine that cutting through the middle produces one north-only piece and one south-only piece.
That picture treats pole labels as materials stored only at the ends. Magnetism is a property of the ordered magnetic regions throughout the magnet, so new cut faces become new poles.
The dependable control is to preserve pole pairing. For every separated piece, mark both ends, use the inherited outer pole, assign the opposite pole to its cut face and test the prediction with attraction and repulsion evidence.
Every ordinary magnet piece has a north pole and a south pole.
The mechanism: what is really happening
A magnet contains many tiny magnetic regions whose effects are aligned strongly enough to produce an overall magnetic field. The labelled ends are where the field pattern emerges most clearly, not piles of north material and south material.
When the bar is divided, each portion retains aligned regions. The original outer ends keep their pole identities, while the newly exposed cut faces act as opposite poles so that each portion forms a complete smaller magnet.
Suppose the original bar reads N on the left and S on the right. After one central cut, the left piece reads N at its outer end and S at the cut face. The right piece reads N at its cut face and S at its outer end.
Pole identity should be tested, not guessed from attraction alone. A known north pole is repelled only by another north pole and attracted by a south pole. Repulsion between two known magnets gives the decisive same-pole evidence.
A compact decision routine
- Copy the original N-to-S orientation.
- Draw each separated piece independently.
- Keep the original outer pole on the piece that contains it.
- Place the opposite pole at each new cut face so every piece has a pair.
- Check with a known test pole and use repulsion to confirm like poles.
Say the routine aloud during practice until it becomes internal: orientation, separate pieces, inherited end, new opposite pole, test. The purpose is not to make every answer slow. It is to make the checking stage reliable enough that speed can grow safely.
Precise worked examples
Worked example 1: one central cut
Prompt. A bar N—S is cut once across the middle.
Reasoning. Each half must remain a complete magnet.
Answer. Left half N—S; right half N—S in the same left-to-right orientation.
Control check. The facing cut surfaces are S on the left piece and N on the right piece.
Worked example 2: three pieces
Prompt. The same bar is cut at two positions.
Reasoning. Each segment retains the local magnetisation direction.
Answer. All three pieces have N at the left end and S at the right end.
Control check. Every segment has two unlike poles.
Worked example 3: reversed orientation
Prompt. Original bar is S on the left and N on the right.
Reasoning. Preserve the original direction rather than a memorised left-N pattern.
Answer. Each piece is S—N from left to right.
Control check. Outer inherited ends remain unchanged.
Worked example 4: rotate one piece
Prompt. The right half is turned around after cutting.
Reasoning. Rotation moves the labelled ends but does not change their identities.
Answer. Its displayed order becomes S—N left to right.
Control check. Turning a magnet does not convert poles.
Worked example 5: north-only claim
Prompt. A pupil labels the left piece N at both ends.
Reasoning. An ordinary bar piece cannot be assigned a single pole type at both ends.
Answer. The cut face must be S if its outer end is N.
Control check. Like labels at both ends violate pole pairing.
Worked example 6: test with known north
Prompt. A known north pole repels a cut face.
Reasoning. Only a north pole gives repulsion against known north.
Answer. The cut face is north.
Control check. Repulsion is the decisive evidence.
Worked example 7: attraction ambiguity
Prompt. An unknown object is attracted to a magnet pole.
Reasoning. It could be the opposite pole of a magnet or an unmagnetised magnetic material.
Answer. Attraction alone does not prove pole identity.
Control check. Test for repulsion with a known pole.
Worked example 8: crushed magnet
Prompt. A magnet breaks into several pieces.
Reasoning. Breaking changes size and shape, not the need for paired poles.
Answer. Each magnetised piece has north and south regions.
Control check. Strength may differ, but pole pairing remains.
Worked example 9: join pieces back
Prompt. Correctly oriented halves are returned to their original positions.
Reasoning. Opposite poles at the cut faces attract.
Answer. They tend to align and attract at the former cut.
Control check. The field arrangement is consistent with the original bar.
Worked example 10: diagram arrows
Prompt. Field arrows are shown without N and S labels.
Reasoning. Outside a magnet, conventional field direction is from north to south.
Answer. Use the stated convention to infer ends.
Control check. Then apply the cut rule to each piece.
Common misconceptions and targeted repairs
Misconception 1: north and south are stored at the tips
Why it happens. The diagram label is treated as a substance.
Targeted repair. Explain aligned magnetic regions throughout the bar.
Micro-test. What happens at a newly cut face?
Misconception 2: cutting removes magnetism
Why it happens. Mechanical division is confused with demagnetising conditions.
Targeted repair. Separate size change from loss of alignment.
Micro-test. Would each piece still affect a compass?
Misconception 3: all left ends are north
Why it happens. Page orientation becomes a rule.
Targeted repair. Copy the original pole direction first.
Micro-test. What if the original left end is south?
Misconception 4: turning a piece swaps pole identity
Why it happens. Position and property are merged.
Targeted repair. Track the physical end while rotating.
Micro-test. Does a named end change material when turned?
Misconception 5: attraction proves south
Why it happens. Magnetic materials can also be attracted.
Targeted repair. Use repulsion with a known pole.
Micro-test. Could iron be attracted too?
Misconception 6: two cuts make only two magnets
Why it happens. Cuts and pieces are counted incorrectly.
Targeted repair. One bar with two complete cuts gives three pieces.
Micro-test. How many separated segments are drawn?
Misconception 7: cut faces receive the same pole
Why it happens. Pairing within each piece is ignored.
Targeted repair. Complete each piece separately.
Micro-test. Does every piece contain unlike ends?
Misconception 8: smaller means no field
Why it happens. Field strength and field existence are confused.
Targeted repair. State that size may affect strength but not the paired-pole pattern.
Micro-test. Can a small compass needle still be a magnet?
Graded independent practice
Attempt each item before opening its explanation in your mind. Write the smallest complete answer that proves the required idea. The questions rise from recognition to explanation and transfer; accuracy matters more than rushing.
Practice 1: recognition
Question. What does one cut through a bar magnet produce?
Explained answer. Two smaller magnets, each with north and south poles.
Practice 2: diagram
Question. Original is N left, S right. Label the left half.
Explained answer. N at its left outer end and S at its right cut face.
Practice 3: diagram
Question. Label the right half of the same magnet.
Explained answer. N at its left cut face and S at its right outer end.
Practice 4: counting
Question. How many pieces result from two complete cuts?
Explained answer. Three pieces.
Practice 5: orientation
Question. Original is S left, N right. What is each piece left to right?
Explained answer. S then N, before any piece is rotated.
Practice 6: rotation
Question. Does rotating a piece change its poles?
Explained answer. No. The pole positions move with the physical piece.
Practice 7: evidence
Question. Known north repels an end. Identify it.
Explained answer. North.
Practice 8: evidence
Question. Known north attracts an end. Is it certainly south?
Explained answer. If the tested object is known to be a magnet, yes; if not, attraction alone may also involve magnetic material.
Practice 9: editing
Question. Correct: “The N half has only a north pole.”
Explained answer. The half has a north pole at one end and a new south pole at its cut face.
Practice 10: editing
Question. Correct: “Breaking a magnet separates north material from south material.”
Explained answer. Breaking creates smaller complete magnets because magnetic regions remain within each piece.
Practice 11: mechanism
Question. Why do new poles appear at cut faces?
Explained answer. Each portion retains aligned magnetic regions and forms its own complete magnetic field pattern.
Practice 12: boundary
Question. Does cutting always keep the same strength?
Explained answer. Not necessarily. Size and damage can affect strength, but each magnetised piece still has paired poles.
Practice 13: boundary
Question. Can attraction alone show that an object is a magnet?
Explained answer. No. Unmagnetised magnetic material can be attracted.
Practice 14: method
Question. What observation is strongest evidence that an unknown end is north?
Explained answer. Repulsion by a known north pole.
Practice 15: transfer
Question. A magnet breaks irregularly. How should pieces be labelled?
Explained answer. Give each magnetised fragment a north and south region according to the original orientation and test where necessary.
Practice 16: transfer
Question. The diagram is rotated vertically. Does the rule change?
Explained answer. No. Follow the original pole direction through the pieces.
Practice 17: reasoning
Question. Why are the two facing cut surfaces opposite?
Explained answer. They belong to different complete pieces whose internal pole directions continue the original orientation.
Practice 18: sufficiency
Question. An end attracts a known north pole. What extra condition makes south certain?
Explained answer. The tested object must be known to be a magnet rather than merely a magnetic material.
Practice 19: planning
Question. How would you test all ends of three pieces?
Explained answer. Use a known pole systematically, record attraction and repulsion, and confirm that each piece has one north and one south end.
Practice 20: exam control
Question. What rule should be written before labelling?
Explained answer. Every ordinary magnet piece has both a north and a south pole.
Delayed transfer: use the idea after the surface changes
Do not repeat these transfer tasks immediately after the worked examples. Leave at least one study session between learning and transfer. Delay removes the comfort of short-term imitation and reveals whether the mechanism can be reconstructed from memory.
Transfer 1: irregular fragments
New setting. A magnet shatters into unequal shapes.
What transfers. Preserve paired poles for every magnetised fragment.
Answer check. Do not assign poles by size.
Transfer 2: rotated drawing
New setting. The original bar is vertical or diagonal.
What transfers. Trace physical orientation, not page directions.
Answer check. Copy the stated starting poles.
Transfer 3: test-magnet experiment
New setting. Labels are hidden.
What transfers. Use a known pole and look for repulsion.
Answer check. Record which ends were actually tested.
Transfer 4: magnetic material trap
New setting. A metal strip is attracted.
What transfers. Attraction does not by itself prove it is a magnet.
Answer check. Seek repulsion.
Transfer 5: multiple cuts
New setting. Several segments are produced.
What transfers. Complete N–S pairing on each segment independently.
Answer check. Pieces equal cuts plus one for complete straight cuts.
Transfer 6: delayed mixed set
New setting. Magnet cutting appears among force and materials questions.
What transfers. Select the pole-pairing model.
Answer check. Separate magnetic identity from mechanical shape.
Build a proof-quality answer
A correct thought can still produce an incomplete written answer. To make your reasoning visible, build the response from three parts: a claim that answers the exact question, evidence drawn from the given sentence, quantities, observation or condition, and a bridge explaining why that evidence supports the claim. The bridge is often the missing part. Learners commonly copy a relevant fact and expect the examiner to infer the connection. Instead, write the relationship explicitly. In a short-response item, each part may be only a phrase; in an explanation item, it may take a complete sentence.
The claim should be no broader than the evidence. If the information proves only what happens in one stated case, do not turn it into a universal rule. If a comparison identifies which value is greater, do not invent the size of the difference. If a word modifies an adjective in one sentence, do not claim that it must have the same job in every sentence. Precision is not timid writing. It is the discipline of matching the strength of the conclusion to the strength of the support.
The evidence should be selected rather than copied wholesale. Ask, “Which detail changes the answer?” A complete prompt may contain setting, names, decorative numbers and contextual sentences that make the question readable but do not justify the conclusion. Circle the smallest decisive detail. Then test it by removal: if deleting the detail would make your answer unsupported or change it, the detail is probably doing real evidential work. If deleting it changes nothing, it may be background rather than proof.
The bridge names the mechanism. Useful bridge language includes “because this means…”, “therefore the two values must…”, “this modifies… rather than…”, “so the rate changes while the starting amount remains…”, and “this fact is relevant but does not establish…”. Do not copy these stems mechanically. Use the one that expresses the actual relationship. A bridge earns its place when it would help a careful classmate see why the evidence, and not some other fact, leads to the claim.
The boundary sentence
After drafting the answer, add a silent boundary sentence in your mind: “This does not yet prove that…” Complete it with the most tempting overstatement. The boundary sentence exposes hidden leaps. For example, an observation over a fixed time does not necessarily prove what happens until completion; a parity condition does not by itself identify two numbers; a familiar suffix does not settle word class; and a relevant detail does not guarantee that all required information is present. You do not always write the boundary sentence in the final response, but thinking it protects the sentence that you do write.
The opposite-case test
Try to imagine a case in which the given evidence remains true but your proposed conclusion becomes false. If such a case is possible under the question’s conditions, the conclusion is too strong or something is missing. This is a powerful test because it turns vague doubt into a concrete counterexample. Keep the counterexample small. Change one feature only, preserve the stated information and see whether the answer survives. When it fails, repair the conclusion or name the additional information that would be needed.
The language-strength ladder
Notice the strength of common answer words. “May” expresses possibility. “Is likely to” expresses a supported tendency, not certainty. “Will” states a definite outcome. “Always” and “never” claim no exceptions within the stated domain. “More than” gives an order; “twice as much” gives a multiplicative comparison; an exact value gives still more information. Choose the lowest rung that fully answers the question and is fully supported. Moving higher without evidence creates error; staying lower when the evidence is decisive creates an incomplete answer.
A diagnostic laboratory for independent learners
Use the following laboratory with four questions from your own schoolwork. Choose one that you answered correctly with confidence, one that you answered correctly by guessing, one that you answered incorrectly, and one that you left incomplete. This mixture matters. Studying only wrong answers can hide fragile success, while studying only correct answers can hide the point at which the method breaks down. Place the four responses on separate pages or separate sections so that you can annotate them without rewriting history.
Pass 1: reconstruct the first decision
Cover the marking and solution. For each item, write the first meaningful decision you made after reading: the word you classified, the relationship you selected, the variable you treated as fixed, or the detail you believed was sufficient. Do not write “I started solving”. Name the decision precisely. Many later errors are consequences of an early classification. Finding that point is more useful than circling the final wrong word because the early decision is what must change next time.
Pass 2: separate knowledge from control
Ask whether the error came from missing knowledge or from failing to control knowledge you already possessed. A knowledge gap means you could not state or reconstruct the needed concept even without time pressure. A control gap means you knew the concept but selected it too quickly, ignored a condition, overgeneralised it or failed to check the conclusion. The repairs differ. Knowledge needs explanation, examples and retrieval. Control needs contrasting cases, decision routines and deliberate checking. Calling both problems “carelessness” prevents either from being repaired.
Pass 3: mark the evidence chain
Use three simple labels beside the response: C for claim, E for evidence and B for bridge. If a label is missing, add the missing part in a different colour. If the response contains two claims, check each one separately; evidence for the first claim may not support the second. If a sentence contains several facts, underline only the decisive one. This annotation makes completeness visible and teaches you to produce an answer whose logic can be checked line by line.
Pass 4: write a minimal repair rule
Finish each analysis with a repair rule of no more than twelve words. It must describe an action you can perform, not a feeling you hope to have. “Be more careful” is not usable. “Name the modifier’s target before naming its class”, “check same parity before halving”, “separate rate from starting amount”, and “list what is still missing” are usable because they tell the brain what to do. Reuse the rule on a new question within two days, then revise it if it does not trigger the right behaviour.
Create your own contrast set
Deep understanding grows when you can create neighbouring cases that require different answers. Start with one correct example from this guide. Make Version A by changing a surface detail that should not change the reasoning. Make Version B by changing one decisive condition that should change the answer. Make Version C by removing a necessary detail so that the answer can no longer be determined or justified. Write the answer and the reason for all three versions before asking anyone to check them.
A useful Version A tests whether you are distracted by appearance. You might change names, rearrange a sentence without changing the modifier’s target, use different whole numbers with the same structural relationship, replace one material with another while keeping the relevant variables controlled, or put a needed clue in a different paragraph. If your method changes merely because the surface changed, you were remembering a picture of the example rather than its mechanism.
A useful Version B changes exactly one controlling feature. The discipline of changing one feature prevents a muddled comparison. After making the change, complete the sentence, “The answer changes because…”. If you cannot name the causal or logical difference, the pair is not yet teaching you anything. Revise it until the difference is visible. This activity is especially valuable for rules with boundaries, because it shows both where the rule works and where another idea must take over.
A useful Version C teaches sufficiency. Remove a value, condition, referent, observation or comparison that the answer requires, but keep enough context for the question to look tempting. Then state exactly what can still be concluded and exactly what cannot. If additional information would make the question answerable, name it. The goal is not to refuse every difficult question. The goal is to distinguish a demanding inference from an impossible one.
Accuracy before speed, then speed with evidence
Do not time the first stage of repair. Work slowly enough to carry out the full routine and produce proof-quality answers. Record which step feels effortful. After three accurate sessions, begin timing small mixed sets, but preserve a separate checking interval. This order matters: speed is repeated decision-making, so practising fast guesses makes the wrong decision more automatic. Practising accurate decisions first gives speed a reliable path to follow.
Track two measures rather than one. The first is answer accuracy. The second is decision accuracy: did you identify the correct target, relationship, controlled variable, evidence gap or boundary even if a later calculation or spelling slip occurred? A learner whose decision accuracy is improving is building a durable method. A learner who gets occasional answers right while decision accuracy remains low is still depending on recognition and luck. Use the two measures to choose the next practice task.
During a timed paper, use a two-pass system. On the first pass, solve questions whose task and evidence chain are clear. Mark uncertain items with a small symbol and move on before one question consumes disproportionate time. On the second pass, diagnose the uncertainty: missing knowledge, missing information, competing interpretations, or an unchecked calculation. Give each type a specific response. This is more efficient than rereading the whole question repeatedly without knowing what you are looking for.
End every practice set with one retrieval prompt: write the central rule from memory, one example where it works, one near-miss where it does not, and one checking question you will ask next time. This four-part exit record takes only a few minutes, yet it converts completed work into a reusable mental tool. On the following day, reconstruct the record before looking at it. The delay shows whether the idea has become available independently or remains tied to the page.
Examination control
1. Copy original orientation. Do not assume north is always on the left.
2. Count pieces. Each complete cut increases the number of pieces by one.
3. Complete every pair. Every magnetised piece needs north and south.
4. Track rotations. Poles move with the physical end.
5. Use decisive evidence. Repulsion identifies like poles.
6. State the boundary. Attraction alone may involve an unmagnetised magnetic material.
A strong examination routine is deliberately modest. It does not ask you to become brilliant in the final minute. It asks you to expose one hidden assumption, one missing unit, one unsupported word or one untested condition before it costs a mark. When time is short, check the exact sentence that carries the conclusion.
A seven-day repair cycle
Day 1 — Diagnose
Complete five short items and mark the exact point at which your reasoning became too broad. Do not merely write “careless”. Name the missing distinction.
Day 2 — Contrast
Place a correct and an almost-correct answer side by side. Underline the word, number or condition that separates them.
Day 3 — Explain
Teach the central rule to an imaginary younger pupil without using the worked example. If you need the original wording, the rule is not yet portable.
Day 4 — Mix
Combine this topic with two unrelated question types. Mixed practice trains recognition because no heading tells you which method to use.
Day 5 — Delay
Return to three earlier items without notes. Reconstruct the routine and record which step was forgotten.
Day 6 — Time
Complete a short set under a calm time limit, then spend a separate minute on conclusion checks. Keep solving time and checking time distinct.
Day 7 — Transfer
Create one new example, one counterexample and one explanation. A learner who can generate all three usually understands the boundary of the rule.
A deeper cut-magnet mastery laboratory
Boundary map
Map cutting, rotating and testing bar magnets into four clear cases, four near-misses and two cases that cannot yet be decided. For each, underline the smallest fact that changes the verdict, then write the extra information needed for every undecidable case.
Teach-back from memory
Close the guide and explain cutting, rotating and testing bar magnets through a rule, a mechanism, one original example, one counterexample and an independent check. Reopen the guide only after the explanation is complete, then repair the earliest missing decision rather than copying the whole page.
Minimal-pair workshop
Create six paired prompts about cutting, rotating and testing bar magnets. Change exactly one word, number, direction, condition or label in each pair so the correct response changes. Solve both versions and name why the altered feature is decisive.
Error classification
Collect eight responses about cutting, rotating and testing bar magnets and classify each error as missing knowledge, wrong classification, ignored condition, execution slip, recording slip or unsupported conclusion. Assign a different repair action to each category and retest with a fresh item.
Delayed reconstruction
After forty-eight hours, reconstruct the rule, routine, three examples and two boundary cases for cutting, rotating and testing bar magnets. Compare with the guide only after writing, then practise the single weak link that disappeared during the delay.
Mixed recognition
Hide two cutting, rotating and testing bar magnets questions among six unrelated English, Mathematics and Science items. Remove headings and solve in a new order. Record the first cue that selected the method and whether that cue was genuinely decisive.
Claim-evidence-bridge audit
Rewrite five answers about cutting, rotating and testing bar magnets as claim, evidence and bridge. Test strong words such as always, never, must and proves. Replace each one that exceeds the stated evidence with a precisely supported alternative.
Alternative-case generator
For three correct answers about cutting, rotating and testing bar magnets, make a surface-change version, a condition-change version and a missing-information version. Solve all nine and state which versions preserve, reverse or suspend the original conclusion.
Confidence calibration
Attempt twelve delayed prompts about cutting, rotating and testing bar magnets and rate confidence before checking. Separate confident-correct, uncertain-correct, uncertain-wrong and confident-wrong responses. Repair confident-wrong items first because their faulty rule is most likely to be reused.
Exam-page simulation
Place one cutting, rotating and testing bar magnets item near the top, middle and end of a mixed page. Complete the page untimed, under a calm limit and again after one week. Compare method selection, evidence control and final recording rather than score alone.
Adversarial case
Ask a parent, tutor or classmate to invent a misleading case about cutting, rotating and testing bar magnets. Think aloud, reject surface clues, name the controlling evidence and state the smallest change that would make the opposite answer correct.
One-week transfer record
Keep one page recording the first cue, chosen method, check and final error for every encounter with cutting, rotating and testing bar magnets. At week end, locate the earliest repeated failure and design one contrasting pair that targets that decision directly.
Topic laboratory 1
Draw an original S-to-N magnet and divide it into four unequal pieces. Label every end before moving anything, then rotate the second piece and flip the fourth. Rewrite the visible left-to-right labels while keeping a record of each physical end’s unchanged identity.
Topic laboratory 2
Design a blind test with three hidden magnet pieces and one known north pole. Create a results table for each tested end, explain why repulsion is decisive, identify where attraction is ambiguous and show how the second end of each confirmed magnet provides a consistency check.
For parents and tutors
Use paper strips so pieces can be cut, moved and rotated physically.
Ask for the original orientation before any labels are added.
Contrast attraction with repulsion using a known test pole.
Retest after a delay with an S-left, N-right starting magnet.
Frequently asked questions
Does cutting isolate a pole?
No. Each piece becomes a smaller magnet with both poles.
What happens at the new faces?
They act as new opposite poles for their respective pieces.
Does turning a piece change north into south?
No. The pole identity stays with the physical end.
How many pieces do two cuts make?
Three, if both cuts completely divide one bar.
Why is repulsion important?
A known pole is repelled only by the same pole of another magnet.
Can attraction prove magnetism?
Not alone, because magnetic materials can also be attracted.
Next routes
Return to the complete volume directory to choose another precise learner problem, or revisit the original PSLE Learning Guide for the earlier foundation. For subject-specific support, continue through the verified PSLE Science route on eduKateSG. These routes are for extending the mechanism, not for replacing your school’s instructions or the official examination document for your year.
Final reminder: Complete north–south pairing on every piece, then use a known pole and repulsion when evidence is required.