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: Measuring gas pressure with a liquid manometer
To determine the pressure of a gas supply using a liquid column manometer.
- Manipulated: Setting of the gas supply (flow rate)
- Responding: Height difference of the liquid columns, h
- Constant: Atmospheric pressure and the density of the manometer liquid
- Graph: A graph is optional. If several settings are used, the gas pressure can be compared with the height difference h to show that a greater h means a greater gas pressure.
- Analysis: When the gas pushes the liquid down on its side, the gas pressure P(gas) = P(atmospheric) + hρg. Convert h to a pressure using hρg and add the atmospheric pressure to obtain the gas pressure.
Experiment: Comparing ohmic and non-ohmic conductors
To compare the current–voltage characteristics of an ohmic conductor (a constantan wire) and a non-ohmic component (a filament bulb).
- Manipulated: Potential difference across the component, V
- Responding: Current through the component, I
- Constant: The component under test (and, for the ohmic wire, its temperature)
- Graph: Plot I (y-axis) against V (x-axis) for both components. The ohmic wire gives a straight line through the origin (constant resistance); the filament bulb gives a curve that bends over.
- Analysis: For the ohmic conductor V / I is constant, so it obeys Ohm's law. For the filament bulb the resistance R = V / I increases as V increases, because the filament gets hotter; it is non-ohmic.
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.
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 Electronics resources
- Chapter overview: Electronics
- Revision Notes
- Common Mistakes
- Practice Questions
- Paper 2 Answering Guide
- Key Terms
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