Physics GCSE: Magnetism and Electromagnetism
Magnetism
Magnetism is an effect that we cannot see, hear or touch. Magnetic fields can be detected when they produce forces. For instance, if you put two magnets close together, they will either push apart or pull together.
There are some simple facts about magnetism that you should know...
A magnet has a magnetic field around it. This field is strongest at its poles, which are at the ends of the magnet. A magnet has two poles, a North-seeking pole and a South-seeking pole. These names are often shortened to North pole and South pole.
The field around a magnet can be represented on a diagram by lines with arrows on. These are called field lines. The closer together the lines are, the stronger the field. The arrows always point from the North pole to the South pole.
- Opposite poles will attract.
- Similar poles will repel.
Use this information to predict whether the following magnets will attract or repel each other:
There are only a few natural elements that are magnetic. The main ones are iron, cobalt and nickel. Many other magnetic materials can be made, by mixing these elements with other substances. A good example is steel, which is a mixture of iron and carbon. Even some plastics are magnetic because they have magnetic substance mixed in them.
Only magnetic materials can be attracted to a magnet, or made into a magnet. Most magnets are made from iron and steel.
Did you know that oxygen is actually magnetic when it is frozen?
So, what is the difference between a magnet and a piece of magnetic material?
The easiest way to tell them apart is that a magnet can repel and attract another magnet. Whereas, a piece of magnetic material can only attract a magnet!
Magnetic materials do not have fields around them, but they are affected by near by magnetic fields.
The earth has its own magnetic field around it. The iron core inside of the earth causes this field. Explorers have been using the Earth's magnetic field to find their way around for centuries. Magnets in compasses spin round until their North-seeking pole points to the North pole on the Earth.
