How to Draw Physics Diagrams That Score Full Marks

Use this guide to draw diagrams that score full marks in Cambridge IGCSE Physics 0625 exams.

Why diagrams matter

In a typical IGCSE Physics exam, 15 to 20 marks depend on diagrams: circuit diagrams, ray diagrams, force diagrams, and experimental setups. Students often lose marks not because they lack knowledge, but because their diagrams are unclear or incomplete.

Circuit diagrams

Rules

• Use a ruler for all straight lines.
• Draw components using standard circuit symbols (the syllabus lists them).
• Place components on the connecting wires, not floating beside them.
• Ensure the circuit is a complete, closed loop.
• Label the values if given (e.g. 6 V, 3 ohm).
• An ammeter goes in series; a voltmeter goes in parallel.

Common mistakes

• Leaving a gap in the circuit (no current can flow).
• Drawing a voltmeter in series.
• Using non-standard symbols.

Ray diagrams

Rules for lenses and mirrors

• Draw the principal axis as a straight horizontal line.
• Mark the focal point(s) on both sides of the lens.
• Draw at least two rays from the top of the object.
• For a converging lens: one ray parallel to the axis refracts through F; one ray through the centre passes straight through.
• Use a ruler for all rays.
• Extend rays behind the lens as dotted lines for virtual images.
• Mark the image position, size, and orientation.

Rules for reflection

• Draw the normal at 90 degrees to the surface at the point of incidence.
• Measure the angle of incidence and angle of reflection from the normal, not from the surface.
• Both angles must be equal.

Force diagrams

Rules

• Draw arrows starting from the object, not from a random point.
• Arrow length represents magnitude: larger force = longer arrow.
• Label every arrow with the force name (weight, friction, normal contact force, tension).
• If forces are balanced, arrows in opposite directions should be equal length.
• Use dotted lines to show the resultant force if asked.

Common mistakes

• Forgetting to include weight (every object near Earth has weight).
• Drawing friction in the wrong direction (friction opposes motion or attempted motion).
• Making the normal force and weight different lengths when the object is in equilibrium on a flat surface.

Experimental setup diagrams

What examiners look for

1. All apparatus is labelled.
2. The arrangement shows how the measurement will be taken.
3. The measuring instrument is in the correct position.
4. The diagram is clear enough that someone could set up the experiment from it.

General diagram checklist

1. Title or label for the diagram.
2. All parts labelled with correct physics names.
3. Ruler used for straight lines (circuits, rays).
4. Arrows show direction (current, ray direction, force direction).
5. Values or measurements labelled where given.