The Coil: A loop of wire (often with many turns) that carries the current. Increasing the number of turns increases the total force and torque produced by the motor.
Permanent Magnets: These provide a uniform external magnetic field. Stronger magnets result in a more powerful motor effect.
Split-Ring Commutator: This is a circular metal ring split into two halves. Its critical role is to reverse the direction of the current in the coil every half-turn (), ensuring the force always acts in a direction that maintains rotation.
Carbon Brushes: These provide a sliding electrical contact between the external circuit and the rotating commutator, allowing current to flow into the coil without tangling wires.
| Feature | D.C. Motor | A.C. Generator |
|---|---|---|
| Energy Input | Electrical (D.C.) | Mechanical (Rotation) |
| Energy Output | Mechanical (Rotation) | Electrical (A.C.) |
| Key Component | Split-ring Commutator | Slip Rings |
| Governing Rule | Fleming's Left-Hand Rule | Fleming's Right-Hand Rule |
The Vertical Position: Always remember that when the coil is vertical (), the brushes lose contact with the split-ring. No current flows, and no force is produced; the motor continues to spin only due to its momentum.
Current Direction: In diagrams, always trace the current from the positive terminal of the battery to the negative terminal before applying Fleming's Left-Hand Rule.
Common Confusion: Do not confuse the 'split-ring' (D.C.) with 'slip rings' (A.C.). The split-ring is essential for D.C. operation to ensure the torque doesn't reverse every half-turn.
Sanity Check: If a question asks how to reverse the motor, remember that reversing BOTH the current and the magnetic field will result in the motor spinning in the SAME original direction.
