The Electric Motor [H]

The electric motor converts electrical energy into kinetic energy using the motor effect. In this lesson you will learn how a simple DC motor works, the role of the split-ring commutator, and how to increase the speed of a motor. This is Higher tier content from AQA GCSE Physics specification 4.7.2.

---

How a Simple DC Motor Works

A simple DC motor consists of:

• A rectangular coil of wire mounted on an axle so it can rotate.
• A permanent magnet providing an external magnetic field.
• A split-ring commutator — two half-rings of copper connected to the ends of the coil.
• Carbon brushes — pressed against the commutator to maintain electrical contact as the coil rotates.
• A DC power supply providing the current.

graph TD
    subgraph "Simple DC Motor"
        PS["DC Power Supply"] --> B1["Carbon Brush (left)"]
        B1 --> SR["Split-Ring Commutator"]
        SR --> COIL["Rectangular Coil (rotates between magnets)"]
        COIL --> SR
        SR --> B2["Carbon Brush (right)"]
        B2 --> PS
        N["N pole (left magnet)"] -.->|"Magnetic field"| S["S pole (right magnet)"]
    end

---

Step-by-Step Explanation of Motor Operation

Step 1: Current Flows Through the Coil