Motor effect
A wire carrying current in a magnetic field feels a force. Reversing the current or the field reverses the force. A coil between two magnets will spin, which is how an electric motor works.
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Analogy
The wire is pushed sideways, like a hand shoving a door.
In practice
Electric motors in fans, washing machines and electric cars use this effect.
Practice
Flashcards
- What is the motor effect?A current-carrying wire in a magnetic field feels a force.
Interview questions
- Explain how an electric motor works.
- A current-carrying coil sits in a magnetic field
- Each side of the coil feels an opposite force
- The coil rotates
- A split-ring commutator reverses the current every half turn
Questions people ask
How can the force on a wire in a magnetic field be made bigger?
Increase the current, use a stronger magnet, or use a longer length of wire inside the field. The force is greatest when the wire is at right angles to the field and zero when it is parallel. Fleming's left-hand rule helps predict the direction.
How does an electric motor keep spinning?
A coil of wire sits between two magnets. Current gives one side an upward force and the other a downward force, so the coil turns. A split-ring commutator reverses the current every half turn, so forces always push the coil round in the same direction.