How to do magnet wire calculations

Written by jason thompson
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How to do magnet wire calculations
(Jupiterimages/ Images)

Magnet wire is designed especially for use in making electromagnets and other solenoids. Magnet wire is made from copper (or sometimes aluminium) and coated with a thin layer of enamel. The enamel provides electrical insulation, so that the wire does not short circuit when wound into a coil. Additionally, because the layer of insulation is thin, many more loops of wire can be fit into a shorter length of solenoid than is possible for normal wires with thicker insulation. Because of this, solenoids made out of magnet wire are stronger than those that aren't.

Skill level:
Moderately Easy

Things you need

  • Ruler
  • Calculator
  • Wire gauge chart

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  1. 1

    Measure the diameter of the coil of magnet wire. Multiply this number by pi, the ratio between a circle's circumference and diameter, which is approximately 3.14. This is the length of magnet wire used in a single loop of the solenoid's coil. Multiply this by the number of turns in the solenoid. This is the total length of magnet wire used in the solenoid.

  2. 2

    Look up the gauge of your magnet wire on a wire gauge chart. Find the resistance per 1000 feet for your gauge. Divide this resistance by 1000 and then multiply it by the length of magnet wire in your solenoid. This is the total electrical resistance of the magnet wire.

  3. 3

    Look up the maximum current in amps for your magnet wire, using the wire gauge chart. Multiply this number by the resistance of the magnet wire in your solenoid. The result is the maximum voltage that you can expose your solenoid to without risk of overheating and fire.

  4. 4

    Divide the diameter of the coil of magnet wire by two. Multiply the result by itself. Multiply this result by pi, 3.14. This result is the area enclosed by the magnet wire. This number is used for calculating the total energy that this solenoid can produce.

Tips and warnings

  • The maximum current that a wire can safely carry varies under different circumstances. A wire sitting in the open air is able to radiate away the heat that it builds up in use. However, a wire that is placed up against something cannot so easily dissipate its heat. In these cases it cannot safely carry as much current as it normally might. Take this into consideration when calculating your maximum safe voltage, if your solenoid is going to be mounted on something.
  • Do not touch any bare wires while they are hooked up to a power source.

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