# How to build a 15,000 Gauss hand-held electromagnet

#### Voltron

Feb 27, 2018
3
Hey guys,

I'm new, and I had a basic question that you can probably help me with.

I'm wondering if it's possible to build a small hand-held electromagnet shaped like a solenoid that is possible of producing a field of 15,000 Gauss.

I'm familiar with the formula for the strength of a field produced by a solenoid: field strength = (permeability * number of turns * amperage) / length.

By my calculations, if I can get a core with a u of 10^(-3), amperage of 5 from a Gates 5 amp-hour battery, and a length of 5cm, I would only need 15 turns.

Am I on the right track?

I've learned though that there's an issue with wattage.

Apparently, because there's such little resistance in copper wire current will flow heavily and the watts will be high.

Too much wattage and the magnet might catch fire or destroy itself.

Any ideas of how to proceed?

Thanks.

#### Externet

Aug 24, 2009
850
"Small hand held" means nothing; What is 'small' ? Like a clothes iron ? A marble ?

A couple of proper permanent rare earth magnets canibalized from defunct hard drives will have that 1.5 Tesla strength. And truly hand-held. No batteries needed. Just attach a handle to its pole piece; do not remove it.

"Issue with wattage"... Watts will be as needed for the desired field. How long should it be energized ? A momentary push button for a fraction of a second ? - minutes ?

Once I made an electromagnet with the core of a microwave oven fed by the Discharge of a 100,000 μF 400V capacitor via a push button, to pull depressed dents on sheet metal. Tricky for certain dents.

#### Voltron

Feb 27, 2018
3
"Small hand held" means nothing; What is 'small' ? Like a clothes iron ? A marble ?

A solenoid the size of a thick bolt. 8 cm long and 2 cm in diameter or so.

A couple of proper permanent rare earth magnets canibalized from defunct hard drives will have that 1.5 Tesla strength. And truly hand-held. No batteries needed. Just attach a handle to its pole piece; do not remove it.

Yes, I'm already aware of that. They seem to be constructed from neodymium.

"Issue with wattage"... Watts will be as needed for the desired field.

How long should it be energized ? A momentary push button for a fraction of a second ? - minutes ?

5 seconds at a time.

Once I made an electromagnet with the core of a microwave oven fed by the Discharge of a 100,000 μF 400V capacitor via a push button, to pull depressed dents on sheet metal. Tricky for certain dents.

What about running a 5 amp-hour lead acid battery through a magnet made from a microwave transformer. Would that work?

#### BobK

Jan 5, 2010
7,682
You get the strongest field with a nearly closed magnetic circuit with only a small gap, which is where the field wiill be strogest.

What do expect to do with this magnet?

Bob

#### Voltron

Feb 27, 2018
3
You get the strongest field with a nearly closed magnetic circuit with only a small gap, which is where the field wiill be strogest.

What do expect to do with this magnet?

Bob

I will use this electro-magnet to manipulate another magnet, a permanent magnet, for a short length of time, maybe for 2 seconds or so.

H
Replies
52
Views
3K
N. Thornton
N
Replies
5
Views
388
Replies
4
Views
365
Replies
3
Views
367
Replies
0
Views
631