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The National MagLab is funded by the National Science Foundation and the State of Florida.

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DC Motor

This simple direct current (DC) motor has been created by pairing a permanent magnet and an electromagnet. The permanent magnet is called a stator because it doesn’t move. The electromagnet is a spinning coil of wire and is often called the rotor. A battery is connected to the circuit, and a magnetic field is created when current flows through the wire. That magnetic field interacts with the field of the permanent magnet, and the coil turns until the two fields are aligned.

A single, 180-degree turn is all you would get out of this motor if it weren't for the commutator. The commutator is a metal ring that has been split, leaving an important gap between halves (represented here in red and blue.) Each half of the commutator is connected to an end of the rotor. Current is delivered to one half of the commutator via the brush. When the brush reaches the gap between halves, the current changes direction. The change in direction reverses the magnetic field (indicated by green arrows here) of the rotor, causing it to spin again to realign with the field of the permanent magnet. This process repeats and the rotor keeps spinning, creating a motor.

Instructions

  1. Find all of the key parts of this system: Stator, rotor, commutator, brush and battery.
  2. Flip the battery to see how it affects the direction of the magnetic field (black arrows) and torque (green arrows.)
  3. Reduce the speed and pause the motion to get a better look at different intervals.

This constant reversal essentially uses the battery, which is a DC power source, to create an alternating current, allowing the rotor to experience torque in the right direction at the right time to keep it spinning.