The places on a magnet where the magnetic forces are strongest are called the poles. These poles are at the end of most magnets. These two poles are different from each other. If the poles of a bar magnet are allowed to swing freely, one will line up facing north and the other will line up facing south. Therefore, the two poles of a magnet are called the north-seeking pole and the south-seeking pole.

The north-seeking poles of two magnets will repel each other. The south-seeking poles of two magnets will also repel each other. However, the north-seeking pole of one magnet will be attracted to the south-seeking pole of another magnet. So for magnets, like poles repel and unlike poles attract. The closer together the magnets, the stronger is this attraction or repulsion.

The north and south-seeking poles of a magnet cannot be separated. If you cut a bar magnet in half, this results in two magnets, each having a north and south-seeking pole. If you cut them again and again, this will always occur.

In a magnetized object it is believed that electrons and protons become lined up opposite each other. For objects which are attracted to magnets, the positive or negative force of the magnet causes these materials to have their protons and electrons line up in a similar, but opposite way. This makes the material the opposite of the pole of the magnet and the two objects attract each other. Metals which are attracted to magnets include iron, cobalt and nickel. However, when the magnet is removed from these materials their protons and electrons go back to their normal alignment, and they are no longer magnetized. The longer they are exposed to the magnet, the longer it takes for these materials to return to their normal alignment. If exposed to a strong magnet for a very long period of time, these material become permanent magnets. However, magnetic properties can be destroyed by heating the materials or by banging the magnet with something, such as a hammer.

The region around a magnet where its magnetic force can act is called a magnetic field. Earth has a core of iron which is a magnet and produces a magnetic field. The needle of a compass is also a magnet. Earth's magnetic north pole is in northern Canada, just north of the Arctic Circle. Earth's magnetic south pole is near the Antarctic Circle. Therefore, Earth's magnetic north and south-seeking poles are not exactly at the geographic north and south poles.

A compass can be used to determine if a wire is carrying an electric current. If the compass is placed near a wire carrying an electric current, the needle of the compass will be deflected from north. This means that an electric current produces a magnetic field. The magnetic field produced by electricity is called an electromagnetic field. A wire that carries electric current has a magnetic field. The stronger the electric current, the stronger the electromagnetic field. However, you can also make the electromagnetic fields stronger by coiling up a wire which carries an electric current. The more wire you have coiled up, the stronger the electromagnetic field. Therefore, the same electric current will have a stronger electromagnetic field if it is going through coiled wire.

The magnetic fields of a coiled wire through which electric current flows can be made even stronger by placing an iron bar inside the coil of wire. An iron bar inside a coil of wire through which electric current is flowing is called an electromagnetic. The electromagnetic is magnetic only when electric current is flowing through the wire. Therefore, an electromagnetic can be turned on or off by turning on or off the electric current. Electromagnets are very useful because of this. They can be used to lift large objects, like cars for example, and when in place the electromagnet is turned off by turning off the electric current. The strength of the magnetic pull of an electromagnetic is determined by two things. The number of coils in the wire, and the strength of the electric current. The more coils, the stronger the electromagnet. The stronger the electric current, the stronger the magnet.

A galvanometer is an instrument which can detect small electric currents. The human nervous system runs on electric current. If a person becomes even slightly nervous, a galvanometer can detect this increase in electric current in the skin. Because of this, the Galvanic Skin Response (GSR) can be used as an emotion detector, and it is one of the measures taken in a polygraph or a lie detector test.

If a magnet can be made using electric current, electric current can be made using a magnet. Wire has electrons which are free to move. The magnet makes them move. When a coil of wire is moved along a magnet, the electrons of the wire will move. This current will change directions if the coil of wire is moved in the opposite direction. This is called induction.

Electric generators produce electric current through electromagnetic induction. A coil of wire is rotated through a magnetic field. This is how LP&L generates the electricity used in homes and businesses.

Magnetism Study Sheet