Electromagnets are magnets created by wrapping wire around a piece of metal and running current through the wire. This activates the electrons in the metal and creates a powerful magnetic force. These magnets will hold until the electricity is turned off. Electromagnets are useful in many practical ways.
Junk yards are filled with many tons of scrap metal that has to be moved out of the way. These pieces of metal are too heavy to move by hand. As a result, most junk yards use electromagnets to move this metal. Large and powerful electromagnets are attached to a wire on a tall crane and lowered to the ground. The metal will stick to the magnet, allowing the crane to move the metal and then the magnet can be switched off to allow the metal to be dropped.
Door bells use electromagnets. Pushing the door bell button turns on an electromagnet, which quickly pulls a piece of metal up against a bell. Releasing the button turns off the electromagnet, causing the metal to fall back into place. As a result, rapidly pressing the button causes a rapid door bell. The same basic principle is used in other bells that don't use bells but buzzers. Pushing the door bell button turns on the electromagnet and activates the buzzer.
Electromagnet locks are a powerful way to keep a door shut. There are a few types of electromagnet locks. One lock creates a powerful electric field between the door and the lock. This field will hold the metal in the lock tightly against the metal in the door, firmly keeping the door in place. Another electromagnet lock pushes a hard metal lock into the door frame, where it will stay in place until the electromagnet is turned off.
Electric motors are dependent on electromagnets. Turning on an electric motor activates the electromagnets. The magnets then push and pull the wheels and gears in the motor, allowing it to run. The motor will then propel the machine it's powering. Applying more electricity to the motor will increase its speed, as the electromagnets push and pull, the wheels and gears move faster. Electric motors are used in many vehicles such as cars or helicopters.
Every speaker relies heavily on electromagnets, including those in your car, radio or television. The speaker cone has magnets around its outer edges. An electromagnet sits opposite the speaker cone and when it's activated it pulls the magnets in the speaker cones, causing the cone to vibrate. These vibrations are then translated into sound waves.