# How to design a Solenoid.

## Main Question or Discussion Point

Hello everyone,
I have a few projects in mind that call for various sized solenoids. I have been experimenting with various gauges of magnet wire, however, every time the battery is connected, it gets too hot to hold. with that being said, is there a way to calculate how many volts and amps a given gauge of wire can handle? I don't know if there are any other variables to consider, but any info will be much appreciated.

P.S I am not sure if something like this has been posted already or not. I searched for solenoids, but came up with nothing.

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UltrafastPED
Gold Member
Much of this information is tabulated; see http://wiki.xtronics.com/index.php/Wire-Gauge_Ampacity

The heating is due to the current and the resistance: power dissipated (as heat) = current^2 x resistance.
As the resistance is so many ohms per unit of length, you can calculate the heat generated per unit of length.

The voltage limit depends upon the insulation, and how well the insulation holds up depends upon the temperature. For the highest loads you should choose transformer wire, which is designed for this type of application.

Solenoid calculators are easy to build, so you can easily find them on the web. For example, see
http://www.calctool.org/CALC/phys/electromagnetism/solenoid

Coil design calculators are less common, but can also be found. See
http://www.daycounter.com/Calculators/Coil-Physical-Properties-Calculator.phtml

The actual application can also make a difference - limitations on size, materials, available cooling, etc. are all important.

Hello UltrafastPED, Thank you for your reply. I have looked up the info you gave me as well as a few other places. I think I kind of understand what you are saying. So what I would like to do is put all the pieces together for you, and see if I got it right. I assume that a high amperage is what cause things to overheat. so if I know my voltage and the resistance, I can use I=V/R to get the amount of amps going through the wire. and then from there I look at the amp tolerance of the wire to get the right sized gauge or a resistor as not to overheat the wire or battery. I don't know if that is correct or not.

jim hardy