Paper 3 at a glance
- Paper 3 carries 15 marks
About this chapter
The DSKP lists no Paper-3 style experiment for this chapter; its Paper 3 relevance is the shared skills below. Practise them on these experiments from the same form:
Experiment: How the length of a wire affects its resistance
To investigate the relationship between the length of a wire and its resistance.
- Manipulated: Length of the wire, l
- Responding: Resistance of the wire, R
- Constant: The cross-sectional area and material of the wire, and its temperature
- Graph: Plot R (y-axis) against l (x-axis). A straight line through the origin shows the resistance is directly proportional to the length.
- Analysis: Since R = ρl / A, the resistance is directly proportional to the length when the area and material are unchanged. The gradient of the R against l graph equals ρ / A.
Experiment: Determining the e.m.f. and internal resistance of a dry cell
To determine the electromotive force (e.m.f.) and the internal resistance of a dry cell.
- Manipulated: Current drawn from the cell, I
- Responding: Terminal potential difference, V
- Constant: The same dry cell
- Graph: Plot V (y-axis) against I (x-axis). The points give a straight line with a negative gradient; the intercept on the V-axis is the e.m.f. and the magnitude of the gradient is the internal resistance.
- Analysis: The terminal voltage obeys V = ε − Ir. The intercept of the V against I graph on the V-axis gives the e.m.f. ε, and the magnitude of the gradient gives the internal resistance r.
Experiment: The effect on a current-carrying conductor in a magnetic field
To study the force that acts on a current-carrying conductor placed in a magnetic field and how it depends on the direction of the current and the field.
- Manipulated: Direction of the current (and of the magnetic field)
- Responding: Direction in which the conductor moves
- Constant: The magnetic field strength and the conductor used
- Graph: No graph is needed because the results are qualitative. The observations are compared with Fleming's left-hand rule.
- Analysis: A current-carrying conductor in a magnetic field experiences a force produced by the interaction (catapult) of the two fields. Its direction is given by Fleming's left-hand rule; reversing the current or the field reverses the force.
Paper 3 skill checklist
- Table: quantities with units in the headings, consistent decimal places, derived column calculated correctly.
- Graph: axes labelled with unit, scale using more than half the grid, points plotted with a sharp pencil, best-fit line.
- Gradient: a large triangle on the line, coordinates shown, unit of the gradient stated.
- Relationship: "y increases linearly with x" or "y is directly proportional to x" only if the line passes through the origin.
- Precaution: one that improves accuracy, stated with its reason.
More on graph skills
Exam tip
Units on every calculation line; no formula is provided in the SPM Physics papers.
More Quantum Physics resources
- Chapter overview: Quantum Physics
- Revision Notes
- Common Mistakes
- Practice Questions
- Paper 2 Answering Guide
- Key Terms
- Calculation practice sets
Source: DSKP KSSM Physics Form 4 and 5 (Versi English), Sijil Pelajaran Malaysia: Format Pentaksiran mulai 2021, Fizik (4531) (Bahagian Pembangunan Kurikulum (BPK), KPM)
Written by the spmphysics.com.my editorial team.· Updated 5 Sept 2026