# Types of dipoles and their fields

1. Oct 16, 2015

### Isaac0427

Hi guys! Sorry for all the questions on electromagnetism. My understanding is that an electric field exists in electric monopoles and dipoles, as well as moving magnetic dipoles, and magnetic fields only exist in magnetic dipoles and moving electric dipoles. Is this correct? There are 2 parts of that that I am not sure about: Is there an electric field in a non-moving magnetic dipole, and is there a magnetic field in a moving electric monopole? Thanks in advance!

2. Oct 16, 2015

### Staff: Mentor

No. You have to have a changing dipole.

Yes. This is described by the Lienard Wiechert potentials.

3. Oct 16, 2015

### Chandra Prayaga

There is a problem in the way you stated it. The fields don't exist "in" the dipoles, etc., but are generated by, and exist all round them, in empty space. A moving magnetic dipole generates an electric field in the following way. The moving magnetic dipole changes the magnetic field at any given point in space, and the changing magnetic field generates an electric field according to Maxwell's equations. Whether a stationary magnetic dipole generates an electric field depends on how the magnetic dipole is structured. For example, a rotating charge is a magnetic dipole, and it generates both a magnetic field and an electric field. An electric monopole is just a point charge, and a moving point charge does generate a magnetic field.

4. Oct 16, 2015

### Isaac0427

Thank you.

5. Oct 16, 2015

### Isaac0427

Ok, and jut to make sure, the difference between a magnetic and electric dipole is if there is any distance between the 2 poles. Correct?

6. Oct 16, 2015

### Staff: Mentor

No. Magnetic dipoles are formed by small loops of current. Electric dipoles are formed by positive and negative charges separated by a small distance.

7. Oct 16, 2015

### Isaac0427

Then how can a 2-sided magnet be a magnetic dipole?

8. Oct 16, 2015

### Isaac0427

Ok. I see what I got wrong. What is really misleading me are the pictures of current loops. They all draw the same field lines, however some sources say that the field lines show the magnetic potential, and some say the field lines are showing the magnetic field.