The first magnetic-field question is not about a diagram
A compass needle beside a straight wire has turned. The student must decide whether that movement was caused by the current, the Earth’s magnetic field, a nearby magnet or an unrecorded change in the apparatus. Good Physics begins by making the comparison that separates those explanations. This guide teaches students to read a current-produced magnetic field, trace its direction, describe the effect of reversing the current, and build a disciplined answer from observations rather than memorised arrows.
The immediate method is to establish a baseline with the current off, arrange a known direction of conventional current, note the compass direction and position, then make one deliberate change and observe again. A wire and a solenoid do not have identical field patterns. A compass shows local field direction, not the source of a field by itself. A larger deflection is useful evidence under controlled conditions, but it is not automatically a numerical measurement of field strength.
This new chapter begins after Volume 0491’s optics evidence audit. The same habit travels to magnetism: trace the physical direction before accepting the label. The previous case concerned light paths and angles at an interface; this one concerns magnetic-field direction at a specified location and a specified current. It is a new syllabus idea, not a second article about critical angles.
The 2027 SEC syllabus and the scope of this lesson
The first Singapore–Cambridge Secondary Education Certificate examinations begin in 2027. The official SEAB G3 list, updated 26 October 2026, identifies standalone G3 Physics as K323, with 6091 as its pre-2027 reference code. G3 English Language is K300 and G3 Mathematics is K310. This guide focuses on the K323 outcomes for magnetism and electromagnetism: compass determination of magnetic-field direction; field patterns of straight current-carrying wires and solenoids; changes in current magnitude and direction; and the application of electromagnets. These outcomes appear in the official Physics syllabus.
For standalone G3 Physics, the published scheme has Paper 1 multiple choice, 40 marks in one hour, contributing 30%; Paper 2 structured and free response, 80 marks in one hour 45 minutes, contributing 50%; and Paper 3 practical, 40 marks in one hour 50 minutes, contributing 20%. They are separate Physics papers. This page’s invented practice situations are teaching examples, not actual SEAB questions or a promise about a future paper.
The scientific difference between magnetic fields, electric fields and electrostatic charging matters. If a student cannot separate these, revisit Volume 0319 on static charge before beginning. A moving charged particle may be involved in electromagnetism, but the examination task may simply ask for the field around an ordinary current-carrying wire. Use the model appropriate to the question.
What the magnetic field means
A magnetic field is a region in which magnetic materials, magnets or suitable moving charges can experience magnetic effects. Field lines are a representation, not physical strings. Their arrows show the direction in which a free north-seeking pole would point at that location. Close field lines conventionally indicate a stronger field when comparing the same kind of diagram, but a drawing without a scale does not establish a precise field magnitude.
The north-seeking end of a compass needle aligns with the resultant magnetic field at the needle. ‘Resultant’ is essential: it includes the field from the experimental wire or coil, the Earth and any other important nearby sources. The compass cannot by itself tell the student which source produced the field. A reliable experiment changes the suspected source while holding other conditions reasonably steady.
Outside a simple bar magnet, magnetic field lines run from the north pole towards the south pole. Within the magnet, they complete closed loops. For a long straight wire carrying steady current, the field curves in circles around the wire. For a solenoid, the field resembles that of a bar magnet, with a comparatively uniform interior region in an idealised long coil and a more spread-out external return path.
The direction rule must be anchored to a viewpoint
For a straight wire, apply the right-hand grip rule to conventional current: the right thumb points in the conventional current direction and the curled fingers indicate the circular magnetic-field direction. Do not say ‘clockwise’ or ‘anticlockwise’ without saying from which end the wire is viewed. A diagram viewed from above can look reversed when viewed from below, even though the physical arrangement has not changed.
An arrow marked with a dot can indicate a vector pointing out of the page; a cross can indicate one pointing into the page. Those symbols are only useful when the diagram’s convention is clear. Translate dot and cross into the spatial direction first. Then apply the grip rule, and finally check the result using one specific compass location. This prevents a memorised arrow from taking control of the reasoning.
For a current-carrying solenoid, curl the fingers of the right hand in the direction of the conventional current around its turns; the thumb points towards the magnetic north end of the coil. Alternatively, identify the field direction inside the coil and then sketch its external return lines. If a question supplies winding direction rather than a labelled current arrow, resolve that physical direction before declaring which end is north.
What changing the current does and does not prove
Reverse the conventional current in the same wire without moving the apparatus and the magnetic-field direction reverses. If the setup is otherwise unchanged, this is a strong comparison because it holds position and geometry fixed. Increasing the current magnitude generally strengthens the magnetic field at a fixed location in the same arrangement. It does not reverse the field unless the current direction also reverses.
An observed needle deflection is not necessarily directly proportional to current. The Earth’s field remains present, and the needle angle results from the combination of fields. A student’s graph of deflection against current may therefore have curvature or an offset. A claim of exact proportionality needs an appropriate measurement model and enough data. For a Mathematics investigation, the correct question is whether the observed table supports a stated model, not whether the graph looks pleasing.
Placing a suitable soft-iron core inside a coil can strengthen its magnetic effect by magnetisation; this involves a material change as well as a geometric one. Changing core and current simultaneously prevents a clean comparison. Also distinguish a temporary magnet, such as soft iron in many applications, from a more persistent permanent magnet, such as steel. The ideal labels do not make real materials identical.
A supervised investigation that produces usable evidence
A teacher can provide a low-voltage school power supply, an insulated current-carrying wire or coil, a compass, suitable support and a switch. Students should follow their school’s electrical and laboratory safety instructions. Avoid mains electricity, exposed high-current conductors and prolonged energising of a coil that may heat. The theoretical explanation is valuable even where students practise with a teacher-provided drawing instead of building a circuit.
First identify the current path and the direction of conventional current. Record the compass reading before energising the wire; this is the baseline. Keep the compass at a marked location, take a reading with current in one direction, switch off, reverse current using the teacher’s approved arrangement and repeat at the same location. Record not only the angles but also the viewing direction, distances, current and equipment positions.
Whenever the reading changes unexpectedly, stop interpreting and check the setup. Has the compass shifted? Was the wire lifted? Is another magnet closer? Was the current actually reversed? Did the supply change magnitude? This is not wasted time. Those checks determine whether the scientific conclusion has an evidential foundation.
How to answer a structured question clearly
A short ‘state’ question may need a precise observation: ‘Reversing the current reverses the direction of the magnetic field around the wire.’ An ‘explain’ question needs a reason linked to the physical process: the direction of the field produced by the wire depends on conventional current direction. An ‘infer’ question about a compass reading may require a condition: the observation is consistent with a reversal if all relevant positions are unchanged.
For a drawn field, write the direction beside at least one point before attempting the whole pattern. Check the right-hand rule, the relative positions and the arrows. Do not confuse a magnetic field line with the circular path of moving electrons. The line is a model of direction; it is not a track along which an electron must travel.
If the command asks for an improvement, name a cause of unreliable evidence and a specific remedy: ‘Mark the compass position so that distance from the wire remains constant during current reversal.’ ‘Repeat the measurement’ is weaker unless you say what will be measured and why repetition helps. Physics marks reward the relationship between the change, observation and conclusion.
Read the evidence without making a stronger claim than the experiment
Imagine that a student’s notebook records a compass direction of 020 degrees with no current, 056 degrees with current direction A and 341 degrees with direction B. The directions are illustrative. They show changes from the initial bearing, but they do not allow the reader to infer an exact field strength in teslas. A good answer says that the needle responds differently in the two current conditions and that the pattern is consistent with an altered resultant magnetic field, subject to the setup.
A second student says, ‘The needle moved 36 degrees, so the field became 36 units stronger.’ This is a unit error and a conceptual error. Angles measure direction or deflection, not magnetic strength. Even with careful measurements, turning an angle into field magnitude would require a justified model and known background field. The exam-safe correction is to keep the observation and discard the invented conversion.
The same principle appeared in the PSLE science guide on keeping a claim inside its evidence. A secondary student extends that habit by stating variables, identifying a physical model, applying it to a new geometry and judging what measured quantities actually establish.
A compact progression for a revision session
Spend the first ten minutes sketching straight-wire fields with the current into and out of the page. Spend the next ten sketching a solenoid, its north and south ends, and the path of an outside field line. Spend ten minutes reading a fictional compass table for changes, confounders and invalid interpretations. Finish by answering two short questions in complete sentences: one on reversal and one on a fair test. Use the last five minutes for checking symbols, the observer’s viewpoint and the difference between field direction and strength.
Return to the Physics learning owner for the wider sequence of fields, currents, forces and electromagnetism. This guide is a focused exam practice route. It does not replace a teacher-supervised practical or the full official syllabus.
Exam clinic 01: No-current baseline
A compass points northeast before the circuit is switched on. A student calls that reading a failure because the needle did not point north on the page.
The page’s top is not automatically geographic north. The compass is showing a field direction in the room. Mark the baseline bearing and keep the paper fixed. The meaningful comparison is the difference after the current is deliberately changed.
What to practise: Explain why a baseline reading is needed before attributing a subsequent deflection to the wire, and state what must remain in place. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 02: A wire moved with the switch
The observer turns on the supply but also lifts the wire two centimetres away from the compass. The subsequent smaller deflection is blamed on the current.
Two variables changed: energising the wire and distance from the compass. A smaller field contribution could result from the changed distance. Repeat with fixed geometry before comparing switched conditions.
What to practise: Name both changed variables, choose the independent variable that answers the question and describe one concrete way to fix the other. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 03: Viewing side forgotten
A drawing says the field is clockwise when the current points towards the student, but the answer gives no viewing direction.
Clockwise is a view-dependent statement. From the opposite side the same circles appear anticlockwise. A strong response begins with the point of view or uses the dot/cross symbol with a consistent right-hand rule.
What to practise: Draw a dot for current out of the page and identify field direction as viewed from the front of that page. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 04: Right hand used backwards
A learner curls the right-hand fingers along the direction of the current in a straight wire and points the thumb around it.
The rule has assigned the jobs to the wrong parts of the hand. For a straight wire, thumb represents conventional current; fingers curl around the wire in the magnetic-field direction. This is a direction rule, not a description of actual finger-shaped physical lines.
What to practise: Explain the grip rule correctly in one sentence and verify a field arrow at a named location on the paper. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 05: Arrow representing electron flow
The circuit diagram labels an electron-flow arrow, but the student treats it automatically as the conventional-current arrow.
Electron movement in a metallic conductor is opposite conventional current. Read the label before applying the right-hand rule. A diagram that specifies electron flow and one that specifies conventional current require careful translation.
What to practise: Write a two-step conversion from electron-flow direction to conventional-current direction and then to the field arrow. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 06: Dot and cross swapped
A dot in the middle of a circle is labelled ‘into the page’ in the key.
The standard dot resembles the point of an arrow approaching the viewer; a cross resembles the tail moving away. Incorrect labelling reverses all derived directions. Fix the symbol key before marking a student’s directional explanation.
What to practise: State the meanings of dot and cross and describe how a wrong legend affects a whole set of otherwise consistent answers. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 07: Compass influenced by a magnet
An iron bar magnet is placed on the desk just before the second current reading.
The bar magnet produces its own field. The compass then responds to the combined fields, so the comparison can no longer isolate the current effect. Remove or control the other source and repeat the same conditions.
What to practise: Identify the confounding factor and write the narrower statement that remains supported by the notebook. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 08: A compass exactly at the wire
The task describes placing a compass exactly at the centre of a thick wire and asks for a simple external circular-field direction.
The ideal long straight-wire diagram is normally interpreted at points around the conductor, not by pretending the needle can occupy the same location as solid metal. Place the observation point outside the conductor and define it clearly.
What to practise: Redraw the question with a compass at a specified location to the right of the wire, then show the relevant circular tangent. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 09: A solenoid treated as a straight wire
The student sketches isolated concentric circles at every point outside a solenoid and calls that its overall field.
Each turn contributes to the combined field. The result for a long solenoid resembles a bar-magnet pattern: a coherent interior field and an external return. Do not paste the field of one straight section over the full coil.
What to practise: Draw the interior and exterior fields, labelling the approximate direction without claiming the ideal pattern is exact at the ends. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 10: Polarity guessed from appearance
A student labels the left end of an unpowered coil as north because it is coloured red in the diagram.
Coil colour and position do not establish magnetic polarity. Determine the direction of conventional current around its turns from the supplied circuit arrows, and apply a consistent coil rule. Without current information, say what cannot be inferred.
What to practise: List the missing information needed to assign the poles and distinguish that from a permanent bar magnet with marked ends. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 11: Current reversed in a solenoid
A coil keeps the same winding and location while the circuit’s conventional-current direction is reversed.
The current-produced magnetic field reverses, so the north and south ends of the energised solenoid interchange. The field is not necessarily zero at the moment of reversal; discuss the before-and-after steady conditions unless the question supplies transient information.
What to practise: Explain the change to a compass at the same fixed position beside one end of the coil. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 12: Current increased, not reversed
The circuit current changes from 0.20 A to 0.35 A in the same direction at the same coil.
A larger current generally increases the coil’s magnetic effect in a fixed arrangement, without changing its polarity. If data are not supplied, do not invent an exact field ratio or a precise compass angle. State the direction result separately from the magnitude result.
What to practise: Write two short sentences, one about direction and one about strength, and include the fixed-geometry condition. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 13: Turns changed together with current
The first trial uses twenty turns at 0.2 A, while the second uses forty turns at 0.4 A.
Both coil turns and current changed. A stronger lifting effect cannot be attributed to either variable independently. Compare trials with one factor altered at a time, or explicitly say the experiment tests a combined change.
What to practise: Construct a three-trial plan that holds current fixed for a turns test and turns fixed for a current test. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 14: Iron core inserted without note
A steel nail is replaced by a soft-iron core between the first and second photographs but the caption mentions only the current.
Core material alters magnetisation and may change the response. Name the material and geometry before drawing conclusions. Also do not assume every nail or steel sample behaves identically to a standard soft-iron core.
What to practise: Write a fair comparison that isolates core material, and explain why magnet retention after switching off is relevant. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 15: Needle angle mistaken for strength
A 60-degree compass deflection is entered in a column headed ‘magnetic strength, T’.
Degrees are units of angle, whereas tesla is a unit of magnetic flux density. The observed angular response depends on combined field geometry, not a direct conversion. Retitle the column and reserve tesla for justified measurements.
What to practise: Correct the table heading and explain why numerical precision in degrees does not turn the reading into a field-strength measurement. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 16: A damaged compass needle
The compass needle sometimes sticks near 270 degrees, even when the setup is rotated.
An unreliable instrument can produce a systematic or intermittent error. Check free movement and compare with an independent compass before trusting the reading. A repeat on a defective instrument alone does not make the result reliable.
What to practise: Distinguish a measurement fault from a physical conclusion and propose a targeted instrument check. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 17: Background field ignored
All readings are compared with an ideal drawing whose compass direction is assumed to be zero degrees before the current.
The Earth contributes a magnetic field. The experimental wire changes the resultant field at the compass. Use the measured baseline rather than treating the theoretical wire-only direction as the complete practical observation.
What to practise: Describe the role of the reference condition when a compass reading differs from the ideal field-line arrow. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 18: Current off but needle still turns
A compass is moved from the front of the desk to the edge of the desk after the circuit has been opened.
The needle can turn because its location changed relative to other field sources. It does not prove current is flowing in an open circuit. Restore the original location and verify the circuit state before making that inference.
What to practise: Explain why location and circuit condition must be recorded separately. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 19: Opposite claims from two photographs
Two photographs show a compass pointing differently, but the photographer rotated the camera by 180 degrees.
The visual frame changed. The apparent direction may reverse although the physical needle bearing did not. Use a fixed reference arrow on the apparatus board and report the observation against that reference, not the camera edge.
What to practise: Identify one photographic control that would allow a reader to compare the two images fairly. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 20: Field line touches another line
A drawn magnetic-field diagram makes two lines cross and says the field has two directions at the crossing.
A field at one point has a single resultant direction. Intersecting arrows in an ordinary field-line sketch suggest two directions at that point and make the representation inconsistent. Redraw the paths smoothly and distinguish superposition from multiple independent arrows.
What to practise: Explain what the crossing error communicates and correct the diagram’s representation. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 21: Arrows left out
A learner draws loops around a wire but leaves every line without a directional arrow.
The pattern alone is not enough if the question asks for direction. Add arrows determined from the specified conventional current and viewpoint, not from a guess about the direction of motion of the compass needle.
What to practise: Rewrite the answer to include both the shape and direction of the field. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 22: Density of lines used as proof
One student draws more field lines in a second picture and concludes that the actual magnetic field doubled.
The number of drawn lines is a representational choice. Denser lines can depict a stronger field under a consistent convention, but an arbitrary doubling of lines is not quantitative evidence. Use measured or justified comparative information for magnitude claims.
What to practise: State what a field-line density comparison can communicate and what it cannot establish numerically. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 23: Strong field labelled unsafe
A school caption declares every magnetic field near an electromagnet to be hazardous without considering conditions.
The statement is unsupported by the described experiment. Actual safety depends on equipment, strength, current, heating and exposure conditions. For school demonstrations, follow the teacher’s instructions and avoid making medical or technical safety promises from a compass reading.
What to practise: Replace the absolute warning with a practical, limited supervised-use instruction. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 24: Heating confused with magnetic effect
The coil becomes warm after several minutes and the student claims the increased temperature proves the magnetic field increased.
Resistive heating shows energy transfer within the electrical circuit, not a direct measure of field strength. Temperature may also change circuit conditions. Keep observations in separate columns and do not substitute heat for a magnetic measurement.
What to practise: Design a safer shorter trial and distinguish ‘the coil warmed’ from ‘the magnetic field strengthened’. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 25: One compass as a whole-field map
The class has one compass reading beside the solenoid and sketches the entire external field as though it had measured every point.
A single local direction cannot map the full pattern. Repeat observations at several marked positions, while considering how moving the compass may alter the measured baseline. Compare with a known schematic without pretending the schematic is a measurement.
What to practise: State what additional observations are needed for a credible field-map claim. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 26: An iron paperclip is attracted
A paperclip moves towards an energised coil and a learner concludes that the coil’s north pole must be facing it.
Attraction of suitable iron may occur near either magnetic pole through induced magnetism; attraction alone does not identify north or south. Use a compass or a correctly interpreted marked magnet for polarity information.
What to practise: Explain why attraction is evidence of magnetic influence but not enough to assign the pole. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 27: A permanent magnet not distinguished
A steel object remains magnetised after the supply is switched off and the student calls that proof the current is still flowing.
Some materials can retain magnetisation. An off-current response is not proof of an energised circuit. Check circuit continuity/current independently and explain remanent magnetism when appropriate.
What to practise: Write the alternative explanation and a practical test that distinguishes it. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 28: Numerical graph beyond evidence
A line joins three current-deflection observations and is extended to predict the angle at ten times the tested current.
The prediction is an extrapolation beyond the observed range and the relation between compass angle and field is not automatically linear. Mark the tested interval and avoid claiming the extrapolated value as an observation.
What to practise: Describe why extrapolation and interpolation differ, and state the condition required before either is trusted. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 29: Control student made no change
Two trials differ only in their labels: ‘current A’ and ‘current B’. The actual power supply output was unchanged.
A renamed condition is not a changed independent variable. Record actual current readings or the direction of connection, and show that the intended manipulation occurred. Otherwise the investigation does not test what the caption claims.
What to practise: Specify an observable manipulation check that confirms a true current reversal. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 30: Practical question with no diagram key
The graph uses arrows, crosses and dashed outlines, but none of the symbols is defined.
The student cannot demonstrate a consistent physical interpretation if the mark scheme cannot tell which arrow means current and which means field. Label each symbol in a key and keep that convention in every panel.
What to practise: Rewrite one sample figure caption with clear definitions of current, field and compass-bearing arrows. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 31: Turn-count graph assumed universal
Data show more paperclips picked up for a coil with more turns, and a caption calls the relationship exactly linear for every electromagnet.
The available data may support a local increasing trend, not a universal proportional law. Core saturation, contact differences, clip sizes and current changes may matter. A fair explanation remains within the tested arrangements.
What to practise: Write a cautious conclusion containing the tested range, the observed trend and one limitation. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 32: A field described as an electrical charge
A learner says the wire is positively magnetic on one side and negatively magnetic on the other.
Magnetic field direction around a current-carrying straight wire is not a pair of positive and negative electric charges. Replace the analogy with the correct field pattern and the specified conventional current direction.
What to practise: Contrast the shape of the field around a straight wire with the simplified picture of two poles on a bar magnet. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 33: Exam command ignored
The task asks ‘state how the field changes when the current direction is reversed,’ and the learner writes an entire paragraph about coil heating.
The response fails to answer the specified relationship despite including other facts. One direct sentence earns more clarity: with the same arrangement, the direction of the magnetic field reverses. Add detail only where the command requests explanation.
What to practise: Underline the command and its variable before writing a concise answer. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
Exam clinic 34: Teacher supervision mistaken for scientific proof
A student says the teacher approved the trial, so the field diagram must be correct.
Permission for an activity and scientific support for a conclusion are different. The diagram still needs current arrows, location, the right-hand rule and observational comparison. Authority does not replace evidence in a Physics answer.
What to practise: Separate a safe permission statement from a claim about the measured physical effect. A complete response should name the physical quantity, identify the part of the arrangement that matters and finish with a conclusion at the same level of certainty as the evidence. Where a diagram is involved, label the viewpoint and use conventional current rather than relying on colour, camera angle or remembered slogans.
A worked practice set
Question 1. A compass is fixed beside an insulated vertical wire. The baseline bearing is recorded with no current. When conventional current flows upward, the needle deflects. When it flows downward at the same magnitude, the needle deflects in the other direction relative to its baseline. Explain the result. Answer: the field due to the wire reverses when the conventional current is reversed. At a fixed compass position the resultant magnetic field therefore changes direction. The exact bearings depend on the wire contribution and background field and need not form a perfectly symmetric pair.
Question 2. A student increases current and redraws the same field pattern with arrows reversed. Identify the error. Answer: increasing current magnitude without reversing its direction generally changes the magnitude of the magnetic effect, not its direction. The arrows should keep the direction determined by the current and the viewpoint. Question 3. Two coils use different current and different numbers of turns. Why is a statement about turns alone weak? Answer: the trial changes two factors and cannot isolate the effect of turns.
Question 4. Explain one difference between a solenoid and a long straight-wire field. Answer: the straight-wire field consists of concentric circles centred on the wire, while the combined field of the solenoid resembles that of a bar magnet, with an approximately aligned interior field and external return lines. The exact layout depends on coil geometry. Question 5. Describe how a compass could be used to map field direction. Answer: at each marked location allow the compass to settle, record its north-seeking direction relative to a fixed reference and repeat at other locations, keeping background sources and circuit conditions controlled.
Self-check. Can you draw both current orientations? Can you state why a compass is a local instrument? Can you distinguish field direction from strength? Can you identify a confounder in a trial? Can you explain why a soft-iron core and a reversed current are different manipulations? If any answer is uncertain, repair that specific foundation rather than practising another whole paper.
Final takeaway and the next step
Current-produced magnetism is a good test of whether a learner knows the difference between a representation and an observation. The circle around a straight wire, the bar-magnet-like solenoid and the north-seeking compass are connected, but they are not interchangeable diagrams. The observer’s viewpoint, the conventional-current arrow and the baseline make the explanation coherent.
Next in the sequence, Mathematics will treat the readings from a supervised electromagnet trial as a data-modelling problem: how to compare ratios, test graphs and reject false proportionality. English will then show how to turn supported findings into a concise audience-appropriate speech, before an EMS decision clinic asks whether the entire demonstration should be approved. The science does not become a separate blended SEC paper; each subject contributes a distinct examination skill.
