The magnetic force is similar to the electrical force in many ways. The magnetic force both attracts and repels. The magnetic force arises from magnetic poles. Consider a bar magnet. If suspended, the magnet will act as a compass. One end will point north and the other will point south. The north pointing end is called the north pole, and the south pointing end called the south pole. The north pole of a magnet will attract south poles and repel other north poles. The south pole of a magnet will attract north poles but repel other south poles. Like poles repel, and opposite poles attract. An interesting characteristic about magnets is that a single magnetic pole can never be isolated. You cannot have magnet will just a north pole or just a south pole. All magnets have two poles. Even if you take a bar magnet and break it apart until the pieces are one atom thick, each atom will have a north and a south pole.

The space around a charged particle contains an electric field. If the charged particle is moving, the space around it is further altered to contain a magnetic field. A moving, charged particle produces both an electric and a magnetic field. A magnetic field is always produced by the motion of a charged particle. The greater the speed of the particle, the greater the magnitude of its magnetic field. A magnetic field, like all other fields, stores energy. The ability of a magnet to move another object comes from its magnetic field. But what is moving in an iron magnet to create its magnetic field? The answer is the electrons of the atoms composing the iron. Electrons spin. This spinning gives each electron a magnetic field. In most materials, the electrons spin in opposite directions and the magnetic fields cancel each other out. In iron (and nickel and cobalt, too) the magnetic fields do not cancel out. Each iron atom is a small magnet. The magnetic field of iron atoms is strong enough to cause adjacent iron atoms to line up and from magnetic domains. Each magnetic domain is made up of billions of aligned atoms. In an non-magnetized piece of iron, these domains are not lined up with each other. They all point in different directions. To magnetize a piece of iron, all that must be done is to place the non-magnetized piece of iron into a magnetic field. The magnetic field will pull the domains into alignment. If the magnetic field is strong enough, the domains will be aligned permanently, and the piece of iron will become a permanent magnet. If a magnet is heated or dropped, some domains will fall out of alignment and the magnet will be weaker than before.

Since the motion of a charged particle creates a magnetic field, an electrical current must also create magnetic field. An electrical current running through a piece of wire produces a magnetic field of concentric circles around the wire. If the wire has a loop in it, the concentric circles will become crowded inside the loop, forming a stronger magnetic field inside the loop than around the rest of the wire. If a wire is bent into many loops, the magnetic field can become very strong inside the loops. If a piece of iron is placed inside the coils of a current carrying wire, the domains in the iron will be aligned by the magnetic field. This will produce an even stronger magnetic field. This combination of current and magnet is called an electromagnet. An electromagnet can produce magnetic fields far greater than either an iron magnet or a current carrying wire could produce on its own.

A moving charged particle has its own magnetic field. Therefore, it will interact with the magnetic field of another magnet. A moving charged particle will be deflected by a magnetic field. The force felt by the charged particle is greatest when the particle is moving perpendicularly to the magnetic field. When the particle is moving parallel to the magnetic field, no force is felt by it. The force of deflection on a charged particle by a magnetic field acts in a very strange way. The force of deflection always acts perpendicularly to both the direction of motion of the charged particle and the direction of the magnetic field. The force of deflection is a sideways force. A wire with a current running through it has a magnetic field. Put the wire in another magnetic field, and the whole wire will be deflected. If the direction of the current the wire is carrying is reversed, the wire will be deflected in the opposite direction. These principals underlie the mechanics of the electric motor.

A simple electric motor is, well, simple. A coil of wire is mounted inside a magnet (either a permanent or electromagnet) so that it can rotate. An electrical source is connected to two contacts. The ends of the coil brush against these contacts and the current flows into the coil. The magnetic field rotates the now charged coil. After one half of a turn, the ends of the coils brush against a different contact, gaining a different charge so that the magnetic field continues to push the coil in the same direction.

A compass points north because the earth is a huge magnet, with magnetic poles close to the geographic north and south poles. The magnetic quality of the earth is believed to be caused by electric currents deep in the earth's molten interior. However, there is no firm explanation concerning why the earth is magnetic. The earth's magnetic field is not stable. Periodically, the earth's magnetic field diminishes to zero and then the magnetic poles reverse, so that the north pole is in the geographic south. The last reversal in the earth's poles was 700,000 years ago, and another reversal may occur in just 2000 years. the sun's magnetic field also periodically diminishes and reverses, but on a much shorter time scale than the earth. The sun reverses every 22 years. The earth's magnetic field behaves like all other magnetic fields and deflects charged particles. In fact, earth's magnetic field deflects a lot of charged particles called cosmic radiation. (If these particles weren't deflected, Earth would be a lot more uncomfortable.) Some of these particles get trapped in the earth's magnetic field, forming two doughnut shaped belts, called the Van Allen belts after James Van Allen. When some of these particles dip into the earth's atmosphere, a beautiful display of light called the Aura Borealis occurs.