4.5.5

The d.c. motor

Cambridge IGCSE Physics (0625)  · Unit 4: Electricity and magnetism  · 4 flashcards

The d.c. motor is topic 4.5.5 in the Cambridge IGCSE Physics (0625) syllabus , positioned in Unit 4 — Electricity and magnetism , alongside Simple phenomena of magnetism, Electric charge and Electric current.

This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical).

The deck below contains 4 flashcards — covering the precise wording mark schemes reward.

What the Cambridge 0625 syllabus says

Official 2026-2028 spec

These are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.

  1. Know Know that a current-carrying coil in a magnetic field may experience a turning effect and that the turning effect is increased by increasing: (a) the number of turns on the coil (b) the current (c) the strength of the magnetic field
  2. Describe Describe the operation of an electric motor, including the action of a split-ring commutator and brushes Supplement
Key Concept Flip

A simple d.c. motor has a coil of 50 turns carrying a current of 2.0 A within a uniform magnetic field. Suggest three modifications that would increase the turning effect (torque) on the coil.

Answer Flip

1. Increase the number of turns on the coil (

Example: to 100 turns).<br>2. Increase the current in the coil (. to 4.0 A).<br>3. Increase the strength of the magnetic field (. by using stronger magnets). <br><br>Explanation: The turning effect (torque) is directly proportional to the number of turns, the current, and the magnetic field strength. Increasing any of these increases the overall force.
Key Concept Flip

A d.c. motor uses a coil placed in a magnetic field. State three factors that affect the magnitude of the turning effect (torque) experienced by the current-carrying coil.

Answer Flip

1. The number of turns on the coil.
2. The magnitude of the current flowing through the coil.
3. The strength of the magnetic field.

Key Concept Flip

Explain how a split-ring commutator and brushes enable continuous rotation of the coil in a d.c. motor.

Answer Flip

The split-ring commutator reverses the direction of the current in the coil every half turn. This ensures that the force on each side of the coil continues to act in the same direction (either pushing up or pushing down), maintaining a constant turning effect (torque) and continuous rotation. The brushes make electrical contact with the commutator as it rotates, allowing current to flow to the coil.

Key Concept Flip

State the purpose of the split-ring commutator in a d.c. motor.

Answer Flip

The split-ring commutator reverses the direction of the current in the coil every half rotation, ensuring continuous rotation in the same direction.

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4.5.4 Force on a current-carrying conductor 4.5.6 The transformer

More topics in Unit 4 — Electricity and magnetism

The d.c. motor sits alongside these Physics decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.

4.1 Simple phenomena of magnetism

22 flashcards
4.2.1 Electric charge

20 flashcards
4.2.2 Electric current

12 flashcards
4.2.3 Electromotive force and potential difference

14 flashcards
4.2.4 Resistance

10 flashcards
4.2.5 Electrical energy and electrical power

8 flashcards
4.3.1 Circuit diagrams and circuit components

4 flashcards
4.3.2 Series and parallel circuits

24 flashcards
4.3.3 Action and use of circuit components

6 flashcards
4.4 Electrical safety

10 flashcards
4.5.1 Electromagnetic induction

10 flashcards
4.5.2 The a.c. generator

4 flashcards
4.5.3 Magnetic effect of a current

10 flashcards
4.5.4 Force on a current-carrying conductor

6 flashcards
4.5.6 The transformer

16 flashcards

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