DK Science & Technology: Electromagnetism
An electric current produces magnetism, and a magnet can produce an electric current. The two forces are so closely connected that scientists talk about the single force of electromagnetism. Without it, we would not have an electricity supply, or ELECTRIC MOTORS.
Each electron is surrounded by a force called an electric field. When an electron moves, it creates a second field—a magnetic field. When electrons are made to flow in a current through a conductor, such as a piece of metal or a coil of wire, the conductor becomes a temporary magnet—an electromagnet.
If a coil of wire is placed near a magnet with an unchanging magnetic field, nothing happens. But if the magnetic field is changed, by moving the magnet back and forth or spinning the wire, the changing magnetic field produces an electric current in the wire.
Generators supply us with most of the electric current we use. They turn mechanical energy (movement) into electrical energy. Inside a generator, a coil of wire is spun inside a powerful magnetic field. This creates an electric current in the wire. A large generator can produce enough electricity to run an entire city.
Electric motors are machines that turn electrical energy into mechanical energy to do work. Electric motors can be small, like the motor that turns the fan in a hair dryer, or huge, like the engine that drives a train.
A current turns a conductor into an electromagnet. If the current is reversed, the electromagnetic poles will reverse, too. When the electromagnet is placed near a fixed magnet, the two sets of poles repel and attract each other. This produces a force that makes the conductor rotate (spin) at high speed. This turns a shaft, which then drives a machine.