# Shaping a magnetic field

1. Jul 26, 2010

### TrustyDelux

Hi all,

I have been playing around with some neodymium magnets recently and have found that although they are indeed very strong the 'range' of the magnetic field is not very large.

So I was wondering if there is a way to shape the magnetic field so that the magnets would attract/repel each other from a greater distace.

Hope I've made myself clear! :)

Thanks.

2. Jul 26, 2010

### AJ Bentley

Not in any useful sense.

You can use soft iron to 'conduct' the magnetism much like a wire conducts electricity, but there's no way to get a 'focussed' magnetic beam such as I imagine you are thinking of.

3. Jul 26, 2010

### TrustyDelux

Not really trying a 'beam' more like a 'stretched' field. I read somewhere that you can use sheets of aluminium or copper to do this.

4. Jul 26, 2010

### pallidin

Assuming that you understand that a magnetic field is not emissive(in the sense of a monopole) a magnetic field must have a return path to exist(as we currently understand; could change)

Because of this, options to "stretch" the field is limited, and requires additional components.
Even with additional components, the "stretch" is severely limited.

5. Jul 26, 2010

### K^2

Aluminum or copper will only work for alternating magnetic field.

If you have a permanent magnet, the only thing that will achieve this sort of effect is a superconductor. A superconductor does not allow magnetic fields to pass through it (well, Type I doesn't, with Type II it's a little more complicated, but anyways...). So if you have a superconductor tube, and you put a magnet at one end of it, near the other end, it will be as if the magnet is right there.

6. Jul 27, 2010

### PaulS1950

Does connecting two permanent magnets with a soft iron rod extend the field as if it were a single magnet as long as the overall length?
Would the rod being a different diameter make a difference? (assuming identical size magnets)

7. Jul 27, 2010

### K^2

If you represent the magnet as a pair of magnetic monopoles (yes, they aren't real, but it works as a mathematical trick) then yes, something like that can be done to separate the monopoles further without altering their strengths.

8. Jul 27, 2010

### TrustyDelux

So is the best way to achieve a larger 'range' to shell out and buy bigger magnets? Or does this only increase the attraction/repulsion force?

Last edited: Jul 27, 2010
9. Jul 27, 2010

### Curl

The range is infinite and magnetic fields are divergence free.

If you want to pick up an iron ball from farther away, tape your magnet to a stick and then use that as an extension.

If you want to "collect" field lines inside a solenoid for example, use an iron core.