# Magnetic Dipole Moment does not include the permeability of free space?

1. Jun 7, 2005

### H_man

Magnetic Dipole Moment does not include the permeability of free space???

Hi,

The formula for a magnetic field in a current loop involves the permeability of free space.

But the formula for the magnetic dipole moment which seems to represent the flux through a current loop does not incorporate the permeability of free space.

Whats happening here?

2. Jun 7, 2005

### Meir Achuz

It's just a question of where you put the constant mu0.
It's not usually put in the mag mom. Then mu0/4pi is put into the Eq. for B, just as it is for B due to currents.
The mag mom is NOT the flux through a current loop.

3. Jun 7, 2005

### Crosson

Anything that you measure involving the magnetic moment also involves a magnetics field, and the permeability is included in that magnetic fielc.

4. Jun 7, 2005

### H_man

Thanks for that, though its still not entirely clear.

What exactly is the Magnetic Dipole Moment a measure of then?

I ask this as I know in the Stern Gerlach exp. the Ag atoms experience a torque due to the dipole moments of the electrons being acted upon by the magnetic field into which it enters. And I originally assumed that the dipole moment was a way of stating the magentic field strength of the current loop....

5. Jun 7, 2005

### Crosson

It is a measure of how strong the interaction between that dipole and an external magnetic field would be.

6. Jun 7, 2005

### Gokul43201

Staff Emeritus
Use the analogue of the electric dipole moment. This is simply the charge times a separation. You do not see $\epsilon_0$ anywhere, do you ?

Likewise, there is no reason for the magnetic dipole moment to have $\mu_0$ in it. This is by definition.

Last edited: Jun 7, 2005
7. Jun 8, 2005

### H_man

Thanks guys, its all much clearer now.