How to build a stonger Electro-Magnet

DHS Science

Hover:
"DHS Science i have a question for you, how strong are you trying to make your electromagnet? Are you just trying to run some current through a wire to create a simple electromagnet or are you trying to create the strongest electromagnet you can make??"

I am trying to make the stongest that i can with the supplies that i have.

Averagesupernova:
DHS, you haven't told us what gauge wire you are using in your electromagnet. You are using 1 megohm resistors with a 12 volt battery? There is NO WAY a one megohm series resistor can allow enough current through from a 12 volt battery to melt your wire.

Sorry about not saying the size of wire, it is 6 gauge. And the reason that the batter melt thru the wire last year was because i never used a resistor then. I just ran a wire straight off of the battery thru the coil. That is the main reason why i have so many questions. Sorry.

Last night i went out and bought a pack of 2 resistors that allow 100 ohms and 10W. So if hook both of them up parallel in the line then i should be fine? Because if i do then the power will be divided evenly between the two resistors and will still only allow 10W thru in all, correct?

NoTime

With six guage wire the resistance of the coil will be close to 0.
Power in resistor is E squared times R.
In this case 12^2 /100 = 1.4 watts.

The resistor does not limit watts.
It only provices resistance.

#6 wire should be able to handle about 30A to 40A without heating up too much.

Current in the coil is E/R.
Or in this case 12/50 = 0.24A

You may want to use smaller resistance value.
For 10W resistors 30 ohms is about as low as you want to go with a 12v source.
This provides a safety factor since the 10W rating is only for ideal conditions.

Averagesupernova

Go here: http://www.solenoidcity.com/

Lots of stuff to learn about winding coils here.

DHS Science

If we were to use a power cord from a computer then how much power (amps, volts, watts) would that allow to enter the magnet if we were getting our power straight out of the wall?

Sorry if I am asking stupid questions but I would really like it if we would not burn the school down.

hover

Are you saying how much power would you get out of the wall if you plugged in a power cord and used that?? That all depends on the rating of voltage from the power cord. It should be listed right on it.

DHS Science

The power cord does not give an answer directly if just gives (what appears to me at least) a random configuration of numbers and letters.

Averagesupernova

Why the heck is this still in this section of the forums? Someone move this to electrical engineering.

hover

It should be right on it somewhere. If you can't find it get a volt meter and measure it that way.

ranger

You know there is a feature called "Report Post" on the lower left section of a post (exclamation mark). Just report the thread and request that it be moved.

DHS Science

We decided to use a car battery so it is pushing out 12 volts and the wire that we are using is still getting really hot. In order for the coil to maintain the same strength we hooked a battery charger up to it, which did the job but should we put a breaker (like from a fuse box) in it to help maintain the amount of amps?

ranger

But to use a fuse, you would need to know how much current the wire can handle before it becomes a danger. The amount of amps depend on the wire gauge. There is no use in getting a fuse thats rated for 7 amps when your wire can handle more.

DHS Science

well we have 6 gauge wire and i was going to put a 15 amp fuse in the circut but i am not sure if that is still to many amps

ranger

There are many tables on the internet that will tell you how many amps your wire can handle. Look it up and then you will be able to choose the appropriate fuse rating.

Averagesupernova

There is significantly more to it than just sizing the fuse to the amount of current that the wire will handle. If you wind several hundred turns of #6 onto a large rod and hook it up to a 12 volt battery with a fuse that is sized at the maximum safe current allowed you will most likely blow the fuse right away. The fuse does not 'regulate' the amount of current allowed to flow. It will allow any current to pass up to a given point and then open up preventing the current from flowing. You need to wind enough wire to get enough resistance so that the natural resistance in the wire will not allow more than X current to pass at a given voltage. Naturally this causes problems because to get enough wire wound to get to this resistance we may have a coil with a 5 foot diameter. The link I gave earlier in this thread should explain it well.
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http://www.solenoidcity.com/electrom...E-28-150p1.htm
This link goes to one of their products which shows wire size related to reisistance of the windings related to the duty cycle at various voltages as well as a few other things.

kvmadan

i went through the discussion...i'm making an electromagnet with a cylindrical iron core(2.5 cm dia, 8 cm height)... i used a 12v 1.3ah battery and it got drained in no time !!!! 20 seconds i guess... i'm thinking of buying a 12v 10a battery ... is it necessary? i want the electromagnet to work for 30 mins. what resistor should i use ... will adding bridge rectifiers help ??

ChummyJigger

Hello fellow hobbyist,
I was wondering if using an actual magnet (cylindrically shaped ) as the core itself in an electromagnet would make a stronger magnet, make no difference, or make it weaker......thanks - I look forward to hearing from you guys...........

Vanadium 50

This thread is several years old.