# Lifting magnets

1. Apr 20, 2005

### the magnet man

Can anyone tell me how to i can calculate the amount of load an electromagnet will pull. the electro magnet has 3 poles. 1 pole is the centre core of the magnet (N) there are two adjacent poles which are on either side of the coil which are joined across the other (s) end of the core.

If i can measure the gauss output from the poles and i know the surface area of the poles can i calculate the force in KG it will hold? Is ther a formula i can apply.

Last edited: Apr 20, 2005
2. Apr 20, 2005

### Pieter Kuiper

You first need to calculate the magnetic flux. Assuming that everything consists of iron, the magnetization will not be higher than 2 tesla at the highest currents.

Now consider what happens when you pull on the magnet: a narrow air gap will open, initially with the same magnetic flux as in the closed magnetic circuit. The energy associated with the field in the gap with area A and thicknes t is:
$$\frac{B^2}{2\mu_0} A t.$$

So to widen this gap you need to do work against the magnetic pressure.

3. Apr 20, 2005

### Meir Achuz

Assuming the pole face is flat, and the field B at the pole face is in Gauss.
The force on a flat piece of high mu iron will be F=B^2 A/(2 pi), using Gaussian units for B and cgs for A and F (in dynes). The area A is the smaller of the two areas.
(That is the smaller of the area of the magnet or of the iron.)

4. Jan 5, 2008

### amit_sarda

Measure Magnetic Power

Dear All

i believe the question was not neatly framed, and i would frame the question again.

Case 1
let us assume that there is a magnetic core of D1 diameter and its height be H.
on this, a conduction of diameter d2 is wound like a solinoid such the conductor ID is D3 and OD is D4. it has total N turns. on this conductor a voltage V is applied which results in a current I to pass through this construction.

(Kindly note that this is a practical solinoid and not a theoritical one there L >> d and hence we approximate that ID = OD and B=u0*n*i)

what would be the gauss value at a distance X from the core.

Case 2
how will the formula change when the conductor is changed from round conductor to a rectangular conductor.

Case 3
how will the formula change when the core is rectangular in nature.

we are finding it difficult to relate the practical data with a theoritical formula.