Previously, you read about forces that are transferred during collisions between objects.

Some objects can exert forces over a distance even when objects are not in contact! If you’ve ever played with wooden trains that connect with magnets or hung a paper on your fridge at home using a magnet, you’ve experienced one of these forces.

The force that a magnet exerts on certain materials, including other magnets, is called magnetic force.

You probably have lots of experience with the phenomena of magnetism if you have ever used refrigerator magnets or magnetic toys like those pictured below.

Magnets exert a magnetic force because they are surrounded by a magnetic field.

This field is the area surrounding a magnet where the attractive (pull force) can be detected. At one end of the field is the north and the other the south pole.

If you’ve played around with magnets before, you’ve probably noticed that sometimes magnets pull toward each other and other times they push each other away. This is because opposite poles (north and south) attract each other, but like poles, such as north and north or south and south, repel or push each other away.

In the figure below, you can see the magnetic field surrounding a bar magnet. Tiny bits of iron, called iron filings, were placed on a sheet of paper. When a magnet was placed under the paper, it attracted the iron filings.

The pattern of the iron filings shows the lines of force that make up the magnetic field of the magnet.

Notice the larger concentration of iron filings at two distinct locations in the photograph. These piles of iron filings are located at either end of the bar magnet. This concentration is the location of the magnetic poles and indicates the areas that exert the strongest force.

Notice that the magnetic field lines move from north to south and south to north.

Magnets can either attract matter or repel matter.

If you put two magnets close with the same poles facing each other, they will repel each other.

The pictures below show magnetic field lines between two magnets that are repelling each other.

In the diagrams we are seeing the magnetic field lines in a two- dimensional space, however, an important thing to note about magnetic fields is that they are three dimensional and surround the magnet.

Materials that are attracted by magnetic fields are called ferromagnetic.

Some people think that all metals are magnetic or are ferromagnetic, but this is not true. Most materials, even most metals, are not ferromagnetic.

However, iron, nickel and cobalt are some examples that are ferromagnetic. Steel, which is made from iron, is also ferromagnetic.

Magnetic forces can pass through materials whether they are ferromagnetic or not.

For example, the magnet that will hold your next science test to your fridge door has a magnetic field that passes through the paper (which is not ferromagnetic) and attracts the ferromagnetic steel in your fridge door.