A DC motor is a machine that turns electrical energy into mechanical rotation. Think of it like a spinning fan that keeps turning as long as you keep blowing air into it. In a motor, the “air” is electric current, and the “blowing” is the magnetic field that pushes the rotor (the part that spins).
1️⃣ Current enters the armature through the brushes and flows into the windings.
2️⃣ Magnetic forces act on the current in the windings. The force is given by the Lorentz equation:
\$F = I \times L \times B\$
where \$I\$ is the current, \$L\$ the length of the conductor, and \$B\$ the magnetic field strength.
3️⃣ Torque is produced and the armature starts to rotate.
4️⃣ As the armature turns, the commutator reverses the direction of current in each winding every 90°, keeping the torque in the same direction.
5️⃣ The motor continues to spin as long as the battery supplies current.
The commutator is like a flip‑flop switch that changes the direction of current each time the rotor turns a quarter turn. Imagine a bicycle wheel that keeps turning because you keep pushing it; the commutator is the mechanism that keeps pushing the wheel in the same direction even though the wheel is rotating.
The brushes are the contact points that allow the current to flow from the stationary battery into the rotating commutator. They are usually made of carbon or graphite so they can slide without breaking the connection.
| Component | Function |
|---|---|
| Commutator | Reverses current direction in the armature windings as they rotate. |
| Brushes | Maintain electrical contact with the rotating commutator. |
Consider a small toy car that runs on a DC motor. The battery powers the motor, the brushes transfer current to the rotating armature, and the commutator keeps the torque direction constant. The result is a car that can move forward or backward depending on how you reverse the battery connections. It’s like a tiny electric bicycle that keeps going as long as you keep the battery connected.