# What is a current dipole?

1. Mar 2, 2012

### basheersubei

So I heard the words "current dipole" mentioned in a presentation about modeling the retina and using the ERG (electroretinogram). I understand what an electric dipole means (usually speaking of two point charges with opposite charges). But what exactly is meant by current dipole? All I know is that it is where you have charges flowing in opposite directions at a certain point (?) . I can clearly tell that I don't understand this right.

I've been searching the web for an answer for a while, but I haven't found anything helpful.

I would appreciate it if you point me to an answer (a link to an article that explains it) or give one here.

Thank you for your time.

2. Mar 3, 2012

### tiny-tim

welcome to pf!

hi basheersubei! welcome to pf!
it seems to be a misleading term for a zero-width current with a finite magnetic moment, see http://en.wikipedia.org/wiki/Magnetoencephalography#The_basis_of_the_MEG_signal

it probably comes from mixing the names of the old and modern theories of magnetic moment, see http://en.wikipedia.org/wiki/Magnetic_moment#Two_definitions_of_moment

3. Mar 3, 2012

### sophiecentaur

It's certainly used in Radio antenna work.

4. Mar 4, 2012

### tiny-tim

Here's a useful comment by nicola spaldin, from "magnetic materials: fundamentals and applications", p3 …
Unfortunately, we are going to immediately run into a complication. There are two complementary ways of developing the theory and definitions of magnetism. The "physicist's way" is in terms of circulating currents, and the "engineer's way" is in terms of magnetic poles (such as we find at the ends of a bar magnet). The two developments lead to different views of which interactions are more fundamental, to sightly different-looking equations, and (to really confuse things) to two different sets of units.​

(available free online at

5. Jul 21, 2012

I know this thread is a bit old but I have a question on this topic. In the EEG literature, it is common to discuss scalp electric potentials as arising from current dipoles within the cortex. Firstly, I still don't really get what a current dipole actually is - although I do remember current quadrupoles etc. being mentioned in the multipole expansion for gravitiational waves.

More importantly, I don't see why currents would be the source of electric potentials at the scalp. As far as I was taught electromagnetism, currents cause magnetic fields. It's important to remember that in electrophysiology there are two charge carriers, positive and negative ions, which usually flow in opposite directions in the brain.

6. Jul 23, 2012