Electromagnet energy ?

1. Jun 28, 2012

Austin0

Electromagnet energy ???

Hi i have very little knowledge of electrodynamics so this is probably a no brainer but:

Given an electromagnet holding a ferrous mass suspended in gravity is the electric energy required exactly equivalent to the basis draw with no mass load??

Thanks

2. Jun 29, 2012

Simon Bridge

Re: Electromagnet energy ???

The energy needed to do something is the applied force multiplied by the distance moved (in the direction applied). Since the suspended mass does not move... the electromagnetic energy needed to hold it there is zero.

3. Jun 29, 2012

Austin0

Re: Electromagnet energy ???

Thanks
Does this imply that if the magnet picks something up off the ground through the air that there would be a current increase during the acceleration because work was being done?

4. Jun 29, 2012

Plantis

Re: Electromagnet energy ???

If you will take a magnet and a small piece of iron,for example. Then you may put the piece of iron on a table and try to pick it up by your magnet. Eventually, you will be able to change the position of the piece by lifting in up. At first glance, it seems that you magnetic field did some work. But, there is an energy stored in the magnetic field of your magnet u = B*B/2μ. where, u - energy density, B - magnetic field , μ - magnetic permiability in μ0 units. So, If you will add a piece of iron, it will alter the total magnetic field, so increasing of the potential energy of the piece of iron will be canceled by the decreasing of the magnetic field of the system (magnet + iron).

5. Jun 29, 2012

Simon Bridge

Re: Electromagnet energy ???

As a conductor moves towards a magnet, there will be an induced current - sure.