The force on a current-carrying conductor in a magnetic field, Fleming’s left-hand rule, factors affecting the force, and how a simple d.c. motor works.
5 narrated scenes. Press play, listen and read along — the points appear as they are explained. Use ‹ Prev / Next › or the scene bar to jump to any scene.
Every fan, blender and electric car relies on one fact: a wire carrying current in a magnetic field feels a force.
Narration uses your device’s built-in voice. No sound? Switch to “Captions only” — the captions advance on their own.
See the forces on the coil and the effect of the commutator.
Copy these into your notebook in your own words — that is how they stick.
A current-carrying wire in a magnetic field experiences a force.
Thumb = Force; first finger = Field; second finger = Current.
Current, field strength, length in the field.
No force if the wire is parallel to the field.
Reverse the current or the field and the force reverses.
Coil, magnets, split-ring commutator, carbon brushes.
Reverses the current every half turn so the coil keeps turning.
More turns, stronger magnets, larger current, iron core.
3 quick games on this lesson. Earn XP and badges as you play — your best score for each game is saved. Games are for practice and do not change your exam readiness. More games in the Physics Arcade.
8 items modelled on real CSEC Paper 1 questions. Choose one answer for each, then check. Aim for 80% or better. Work each item on paper first.
Write full answers, then reveal the mark scheme and tick the points you earned (14 marks in total). Show all your working — method marks count. Your answers are saved on this device.
Question 1 [14 marks]
A simple d.c. motor has a rectangular coil between the poles of a permanent magnet.
(a) (a) State Fleming’s left-hand rule. [3]
(b) (b) Explain why the coil begins to turn when a current flows. [3]
(c) (c) State the purpose of the split-ring commutator. [2]
(d) (d) State the purpose of the carbon brushes. [1]
(e) (e) State three ways to increase the speed of the motor. [3]
(f) (f) State what would happen if the polarity of the battery were reversed. [2]
Find these in your own past-paper booklets for extra timed practice. Items above are written in the style of these papers; any adapted from a specific question say so.