Compare Magnetism to Gravity

In physics, we study multiple different forces, such as magnetism, the electrostatic force, and gravity. 

These forces have a lot of similarities and differences, so let's focus on gravity and magnetism, and compare them!

We will start with magnetism. Magnetism is a force that affects magnets and magnetic materials. Magnetic materials are a group of materials that experience the force of magnetism. These materials primarily include iron, steel, nickel and cobalt. 

Magnets have a north pole and a south pole. 

All magnets have a magnetic field around them. A magnetic field is an area where a magnet, or a magnetic material, would experience a force. 

Magnets can attract or repel other magnets, but they always attract magnetic materials. 

We can visualise magnetic fields with diagrams. Depending on the shape of the magnet the field can look a little different. This is the magnetic field around a bar magnet. 

We can see that the lines are curved, and are more densely packed at the poles, indicating a stronger field in that area. 

The field lines always point from north to south. 

We can draw magnetic fields around horseshoe magnets too. 

If we compare, we can see that the field is similarly stronger at the poles of the magnet, and the lines point from north to south. 

We can also compare magnetism and magnetic fields to other forces, such as gravity. 

When we think about gravity, we typically think about the force that causes planets to orbit the Sun, or the force that causes us to have weight and stay on the Earth!

The force of gravity affects any object that has mass (in kilograms). We can describe this using the concept of the gravitational field. 

Any object with mass has a gravitational field. A gravitational field is an area where an object with mass experiences a force. 

This might remind you of the magnetic field - an area where a magnet or magnetic material experiences a force.

The concept of a field is the same, but gravitational fields affect objects with mass, instead of magnets and magnetic materials. 

This diagram shows the gravitational field of the Earth. Field lines point in the direction towards the centre of the Earth. 

The field lines are closer together at the surface of the Earth, and further apart as we move away. This tells us that the gravitational field and gravitational force are stronger the closer you are to a planet. 

This is a bit like the fact that magnetic fields are stronger at the poles!

A difference between gravitational fields and magnetic fields is that gravitational fields and forces are always attractive, but magnetic fields can cause attraction or repulsion. 

Now that we have made some comparisons between magnetism and gravity, let's try some questions!

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