# What is permanent magnet B field equation?

1. Feb 11, 2009

### ShahinPhD

I'm looking for an equation to calculate Tesla (B) between two permanent magnets with distance of 10mm.

Magnets are located in front of each other; disk shape and intensity of each is 1.3T in its core, and 0.6T on surface, so I'm interested how to calculate the B between them in distance of 5mm from each one (10mm between 2 magnets).

2. Feb 11, 2009

### clem

If the magnets are much longer than 5mm, the B field 5mm from the face of one magnet is the same as the E field 5mm from a uniformly charged disk with charge density
$$\sigma=M$$ where M=13,000 gauss (all in Gaussianl units). Just double it for two magnets.

3. Feb 13, 2009

### ShahinPhD

It seems OK, but in a short form I'm looking for a formula to calculate the Tesla in distance between two magnets.
Suppose we have some parameters: dimensions of magnets, power of magnets in core and surface, distance between them; so how can we use a formula to calculate intensity between magnets in some distance?

(Frankly I'm looking for a formula to use for my calculations)

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4. Feb 13, 2009

### clem

The on axis formula for E due to a uniformly charged disk is in most (even elementary) textbooks.