Components:
- Coil — carries current, experiences force
- Magnets — provide magnetic field
- Split-ring commutator — reverses current every half turn
- Brushes — connect power supply to spinning coil
Why the commutator is essential:
- Without it, coil would rotate 180° then stop (or oscillate)
- Commutator reverses current direction every half turn
- This keeps the force pushing in the same rotational direction
- Result: continuous rotation
To make motor spin faster:
- Increase current
- Use stronger magnets
- Add more turns to the coil
Quick Check: A wire carries a current of 3 A in a magnetic field of flux density 0.5 T. The length of wire in the field is 0.2 m. Calculate the force on the wire.
F = B × I × L = 0.5 × 3 × 0.2 = 0.3 N. The force acts at right angles to both the current and the magnetic field direction (use Fleming's Left-Hand Rule to find its direction).
This key facts covers The DC Motor within The Motor Effect for GCSE Physics. Revise The Motor Effect in Magnetism for GCSE Physics with 19 exam-style questions and 12 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 4 of 12 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for The Motor Effect
What is the motor effect?
Explain how Fleming's left-hand rule is used to find the direction of the force on a current-carrying conductor in a magnetic field.