# The Naked Scientists Forum

### Author Topic: How can I make a powerful, yet compact, electromagnet?  (Read 4294 times)

#### Captain

• First timers
• Posts: 1
##### How can I make a powerful, yet compact, electromagnet?
« on: 10/05/2009 19:21:12 »
Hi folks, I've just recently opened my account and was wondering if someone can help me out.

What im trying to do is make a strong electromagnet that could fit into a small space for example a smarties tube. I dont really fully understand the physics behind it but im hopeing someone might have some knowledge to help. Would i need a really big battery to do this or could i use standard AA batterys and create a stong field?

Any information would be great and i think this site is awesome :)
« Last Edit: 15/05/2009 09:25:57 by chris »

#### Vern

• Neilep Level Member
• Posts: 2072
##### Re: How can I make a powerful, yet compact, electromagnet?
« Reply #1 on: 11/05/2009 14:57:16 »
This Wiki article may be helpful

I'm not an expert on electromagnets, but a quick scan of the internet indicates that the key to making a good electromagnet is the core material. You should probably research different materials for their magnetic properties. There are equations that relate the number of turns of wire around the core, the magnitude of current flow, and the strength of the field produced. The field strength will be different for each material.

Main article: Electromagnet

An electromagnet in its simplest form, is a wire that has been coiled into one or more loops, known as a solenoid. When electric current flows through the wire, a magnetic field is generated. It is concentrated near (and especially inside) the coil, and its field lines are very similar to those for a magnet. The orientation of this effective magnet is determined by the right hand rule. The magnetic moment and the magnetic field of the electromagnet are proportional to the number of loops of wire, to the cross-section of each loop, and to the current passing through the wire.

If the coil of wire is wrapped around a material with no special magnetic properties (e.g., cardboard), it will tend to generate a very weak field. However, if it is wrapped around a "soft" ferromagnetic material, such as an iron nail, then the net field produced can result in a several hundred- to thousandfold increase of field strength.

#### syhprum

• Neilep Level Member
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##### Re: How can I make a powerful, yet compact, electromagnet?
« Reply #2 on: 11/05/2009 16:55:27 »
The limit in strength for for a Iron cored magnet is about 2T (20'000 Gauss)all really strong magnets use either superconducting windings or water cooled copper windings dissipating megaWatts.
Don't expect a lot of results with a couple of A cells. Short circuit a A cell into an ampmeter to determine its internal resistance (probably about 1 Ohm)and choose a length of copper wire of the same resistance for your winding choose a length to diameter ratio of about five to one and use all the wire, with this power supply you won't run into iron saturation problems.
It is difficult to measure magnetic field strength without special equipment the best thing would be a Hall effect probe
« Last Edit: 11/05/2009 16:58:39 by syhprum »

#### The Naked Scientists Forum

##### Re: How can I make a powerful, yet compact, electromagnet?
« Reply #2 on: 11/05/2009 16:55:27 »