Motors & the Motor Effect
Explain the motor effect as the force on a current-carrying conductor in a magnetic field, and describe how this principle is used in electric motors and loudspeakers
What a learner can do afterwards
- Explains that a current-carrying conductor in a magnetic field experiences a force (the motor effect)
- Predicts how reversing the current or reversing the magnetic field affects the direction of the force
- Describes how the motor effect is applied in an electric motor and in a loudspeaker
The lesson
You already know a wire carrying current makes its own magnetic field. Now put that wire inside a second magnet's field. The two fields push against each other, and the wire feels a force. This push is called the motor effect.
The direction of the push depends on two things: which way the current flows, and which way the magnetic field points. Reverse either one, and the force flips to point the opposite way. Reverse both at once, and the force ends up pointing the same way it started.
Inside an electric motor, a coil of wire sits between the poles of a magnet. Current flows through the coil, and the motor effect pushes one side of the coil up while pushing the other side down. That pair of pushes spins the coil round.
A loudspeaker uses the same push. Current from an amplifier flows through a coil attached to the speaker cone. As the current changes, the motor effect pushes the coil back and forth, and the cone moves with it, shoving the air to make sound.
To make a motor spin faster or a speaker louder, engineers raise the current or use a stronger magnet. Either change makes the motor effect's push bigger.
A current-carrying wire in a magnetic field feels a push called the motor effect, and reversing the current or the field reverses which way that push points.
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8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.