# Energy In a magnetic field?

1. Apr 26, 2012

### Hypo

Hallo everyone!

I'd like more about the energy in the magnetic fields of a magnet is there major amounts of energy?

I never thought that magnets would have Energy Only thought of its forces thats all.

Can anyone give out an explanation of that energy and is it in anyway useful?

Thanks!

2. Apr 26, 2012

### elegysix

the energy density of a magnetic field is 1/2 B^2/$\mu$
So if you have a region with a magnetic field, you integrate that over the region to find the total energy of the magnetic field.

think of it like a hose - pushing the ends of opposing hoses together is hard because the water is pushing them apart.

The reason there is energy in the magnetic field is the same as the hose - you need energy to have the water flowing.

But these analogies only start to make sense of it, there is no "flowing water" in a magnetic field, unless you're a fan of the old ether theory. Just think of it as a "thing" and whenever there is a "thing", no matter what it does, energy is needed to create it and the energy is stored in it until it is destroyed. Conservation of energy always applies.

3. Apr 26, 2012

### Staff: Mentor

Energy of magnetic fields are important in coils - in fact, this is the reason why coils are built at all.
As an example, the electricity grid relys on coils to transform the electric energy it between different voltages.

The superconducting coils at the LHC can store several gigajoules, this is the same order of magnitude as the kinetic energy of a flying Boeing 747 and enough to supply a small house with electric energy for a significant fraction of a year.