- #1

- 115

- 0

Obviously, two magnets with rectangular faces and side 5 and 6 have more force on each other than two magnets with half that size, because more magnetic field lines interact with each other.

I need an equation

Thanks

You are using an out of date browser. It may not display this or other websites correctly.

You should upgrade or use an alternative browser.

You should upgrade or use an alternative browser.

- Thread starter eddybob123
- Start date

- #1

- 115

- 0

Obviously, two magnets with rectangular faces and side 5 and 6 have more force on each other than two magnets with half that size, because more magnetic field lines interact with each other.

I need an equation

Thanks

- #2

Meir Achuz

Science Advisor

Homework Helper

Gold Member

- 3,529

- 114

F=2pi MM'A, where M and M' are the magnetization of each and A is the are of contact.

In terms of pole strength, it is F=2pi gg'/A.

- #3

- 115

- 0

- #4

- 115

- 0

- #5

- 34

- 0

One thing that you can do is to suppose that they are far apart, and calculate the magnetic force on one magnet (thought as a dipole), due to the magnetic field of the other magnet, also thought as a dipole.

- #6

Meir Achuz

Science Advisor

Homework Helper

Gold Member

- 3,529

- 114

A is the area of contact. In Gaussian units, F is in dynes. Other configurations have different results.

- #7

- 115

- 0

But how do I calculate the force? How do I calculate it in dipoles?

- #8

Meir Achuz

Science Advisor

Homework Helper

Gold Member

- 3,529

- 114

If the are flush together, then post #2 applies.

- #9

- 115

- 0

One thing that you can do is to suppose that they are far apart, and calculate the magnetic force on one magnet (thought as a dipole), due to the magnetic field of the other magnet, also thought as a dipole.

How exactly do I calculate the force? I googled it but I couldn't find a simple formula.

- #10

Meir Achuz

Science Advisor

Homework Helper

Gold Member

- 3,529

- 114

- #11

- 115

- 0

- #12

Meir Achuz

Science Advisor

Homework Helper

Gold Member

- 3,529

- 114

One picture is worth 31 words.

- #13

- 115

- 0

- #14

Meir Achuz

Science Advisor

Homework Helper

Gold Member

- 3,529

- 114

- #15

- 115

- 0

Just so you know, I don't need an exact answer. All I'm looking for is a formula to help calculate these things.

- #16

Meir Achuz

Science Advisor

Homework Helper

Gold Member

- 3,529

- 114

and the distance between the magnets

- #17

- 115

- 0

Say, 1.5 centimetres.

- #18

Meir Achuz

Science Advisor

Homework Helper

Gold Member

- 3,529

- 114

[tex]F=\frac{2\pi R^2 Mm}{(d^2+R^2)^{3/2}}[/tex],

where R is the radius (1 cm} of the cylindrical magnet, M is its magnetization, and d is the distance (1.5+1.1/2) from the face of the cylinder to the middle of the elliptical magnet. This is all in Gaussian-cgs units. You could measure M by the force to separate two identical cylindrical magnets given in post #2. You could measure the magnetic moment m by the torque in a known B field (in gauss)

by torque=m B cos\theta.

This approximation should be reasonable until you get too close together or too far apart, when more complicated formulas would be needed.

- #19

- 115

- 0

What about all the other positions on the rotating pivot? What will happen to the equation?

- #20

Meir Achuz

Science Advisor

Homework Helper

Gold Member

- 3,529

- 114

The formula would be simpler if d>>R.

- #21

- 115

- 0

Okay, I looked it up on the Internet but I don't understand how it fits into magnetism.

- #22

- 115

- 0

- #23

- 2

- 0

- #24

- 426

- 5

Share:

- Replies
- 36

- Views
- 4K