Chapter Twenty-Two: Electricity and Magnetism 22.1 Properties of Magnets 22.2 Electromagnets 22.3 Electric Motors

22.2 Electomagnets Electromagnets are magnets that are created when there is electric current flowing in a wire. The simplest electromagnet uses a coil of wire wrapped around some iron.

22.2 Right hand rule To find the north pole of an electromagnet, use the right hand rule. When the fingers of your right hand curl in the direction of the wire, your thumb points toward the magnet’s north pole.

22.2 Doorbells A doorbell contains an electromagnet. When the button of the bell is pushed, it sends current through the electromagnet.

22.2 Building an electromagnet You can easily build an electromagnet from wire and a piece of iron, such as a nail. Wrap the wire in many turns around the nail and connect a battery.

22.2 Building an electromagnet There are two ways to increase the current in a simple electromagnet: Apply more voltage by adding a second battery. Add more turns of wire around the nail. Why do these two techniques work?

22.2 Similarities in permanent and electromagnets The charged electrons in atoms behave like small loops of current. Electric current through loops of wire creates an electromagnet. Atomic-scale electric currents create a permanent magnet.

22.2 Magnetic materials Atoms act like tiny magnets. Permanent magnets have their atoms aligned, creating the magnetic forces we observe.

22.2 Magnetic materials In iron, the atoms are free to rotate and easily align their individual north and south poles.

22.2 Nonmagnetic materials The atoms in non-magnetic materials, like plastic, are not free to move or change their magnetic orientation.