One application of magnetic fields in household appliances.

Essay by SantinaHigh School, 11th grade September 2005

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One thing that uses magnetic fields is the electric motor, which is used in many household appliances, such as electric fans, microwave ovens, and other small appliances. In this instance the electric motor has an electric current, giving it also this magnetic field.

An electric motor converts electricity into mechanical motion.

Most electric motors work by electromagnetism, but motors based on electrostatic forces also exist. The overarching concept is that a force is generated when a current-carrying element is subjected to a magnetic field. In a cylindrical motor, the rotor rotates because a torque is developed when this force is applied at a given distance from the axis of the rotor.

Most electromagnetic motors are rotary, but linear types also exist. In a rotary motor, the rotating part (usually on the inside) is called the rotor, and the stationary part is called the stator. The motor contains electromagnets that are wound on a frame.

Though this frame is often called the armature. The electromagnetic field works as shown in the diagrams below.

DC motors.

A simple DC electric motor. When the coil is powered, a magnetic field is generated around the armature. The left side of the armature is pushed away from the left magnet and drawn toward the right, causing rotation.

The armature continues to rotate.

When the armature becomes horizontally aligned, the commutator reverses the direction of current through the coil, reversing the magnetic field. The process then repeats.

Single-phase AC induction motors.

Electric motors have no electrical connection between the rotor and the outside world. They operate due to a moving magnetic field induces a current to flow in the rotor. This current flow in the rotor creates the second magnetic field required to produce a torque. The motor was introduced in 1888 and it initiated...