What Is an Electric Motor?
Electric motors are everywhere — inside your phone's vibration function, in electric cars, in washing machines, in fans, and even in the tiny servos inside drones. They are one of the most important inventions in human history, converting electrical energy into kinetic (mechanical) energy.
A device that converts electrical energy into kinetic (mechanical) energy using the interaction between a magnetic field and an electric current.
The principle behind every electric motor — from a tiny hobby motor to a massive industrial machine — is the same: a current-carrying conductor placed in a magnetic field experiences a force. This force is what makes the motor spin.
Think of a motor like two magnets being pushed apart. The wire carrying current creates its own magnetic field, and when this meets the external magnetic field of the permanent magnets, the two fields interact and push the wire sideways — just like two magnets repelling each other. That sideways push is what drives the rotation!
MYP Key Concept — Relationships: The electric motor is a perfect example of the relationship between electricity and magnetism. A changing or interacting magnetic field and electric current are deeply connected — understanding one helps you understand the other. Related Concept — Transformation: The motor transforms electrical energy into kinetic energy, which is why it appears in this unit on energy transformations.
The Motor Effect: Force on a Current-Carrying Conductor
The foundation of the electric motor is the motor effect.
The force experienced by a current-carrying conductor when it is placed in an external magnetic field. This occurs because the magnetic field of the current interacts with the external magnetic field.
For the force to be produced, three things must be true:
- There must be a current flowing through the conductor.
- The conductor must be inside a magnetic field.
- The conductor (or current direction) must not be parallel to the magnetic field lines.
The maximum force is produced when the current is perpendicular (at 90°) to the magnetic field. If the current is parallel to the field, there is no force at all.
The force produced by the motor effect is always perpendicular to both the current direction and the magnetic field direction. This is why the wire moves sideways rather than along the field lines.
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