UNIT FIVE: Electricity and Magnetism  Chapter 16 Electricity  Chapter 17 Magnetism

Chapter Seventeen: Magnetism  17.1 Properties of Magnets  17.2 Electromagnets  17.3 Electric Motors and Generators  17.4 Generating Electricity

Chapter 17.2 Learning Goals  Define electromagnet.  Build a simple electromagnet.  Compare permanent magnets and electromagnets.

Investigation 17B  Key Question: How are electricity and magnetism related? Electromagnets

17.2 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.

17.2 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.

17.2 Electromagnets in Toasters  By changing the amount of current, you can easily change the strength of an electromagnet or even turn its magnetism on and off. A toaster tray is pulled down by an electromagnet while bread is toasting.

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

17.2 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.

17.2 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?

17.2 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.

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

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

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