Magnetism What is magnetism? Magnetism is an invisible force seen when all the electrons spin in the same direction. When you bring two magnets together they exert a push or pull called a magnetic force. This force results from spinning electric charges of electrons in the magnet. The force can either push magnets apart, or pull them together. Magnetic force is one of only three forces in nature that can act at a distance. Gravitational and electrical forces are the other two.

What causes magnetism? As we saw previously, some materials are magnetic, some are not. Why is that? Well first, remember that all matter is made up of atoms. These atoms are made up of 3 smaller building blocks: Protons have a positive charge Electrons have a negative charge Neutrons have no charge. Both the proton and neutron are in the nucleus while the electrons circle around the nucleus.

What causes magnetism? As an electron spins, it induces (makes) a magnetic field. In magnetic materials, the electrons move in the same direction. Electrons do not cancel out in magnetic materials. In nonmagnetic materials, like the magnetic fields of the electrons cancel each other out. The electrons are flying around randomly.

Magnetic Fields Magnetic field = area around the magnet where magnetic forces can be detected. A magnetic object placed in this field will be affected by the magnet. The magnetic field is arranged in lines called magnetic field lines (or flux lines). Magnetic field lines enter at the south pole, and exit at the north pole. Magnetic field lines connect points of equal magnitude. Magnetic field lines do not cross each other. The magnetic force is strongest where the lines are most concentrated (near the poles). The further from the poles, the weaker the magnetic field. Iron filings next to a magnet

Magnetic Poles Every magnet has a north pole and a south pole. If you place the north poles of two magnets together they will repel or push apart. If you place the north pole of one magnet facing the south pole of the other magnet, they will attract. Law of Magnetic Poles = like poles repel each other, and unlike poles attract each other.

Magnetic Earth The Earth is like a giant magnet. The spinning molten iron and nickel in the outer core induce a magnetic field called the magnetosphere. So if a compass is a tiny magnet, why does the north end of a compass needle point to the Earth’s magnetic north if like poles repel? Look at the Earth’s field lines. They enter at the magnetic north pole and exit at the magnetic south pole. How does that compare to what you learned about field lines? Don’t field lines on a magnet enter at the south pole and exit at the north pole? The north pole of a magnet like a compass gets its name because it points towards the Earths geographic north. The Earth’s magnetic north pole would actually be a south pole on a magnet.