How to Calculate Winding Resistance
Calculate the resistance of a set of electrical windings to know how well they limit current flow. Windings consist of a long wire wrapped around a cylindrical base. They often appear in solenoids to generate a magnetic field. Resistance of a wire is measured in ohms and determines the ability to dissipate electrical current. The resistance of the windings is related to the length of the wire, the area of the wire's ends and the resistivity of the wire material. Resistivity measures the ability of a substance to limit current based on its atomic structure.
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Instructions
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1
Measure the length and diameter of the wire that forms the windings in inches. For this example, the length and diameter are 130 inches and 0.25 inches, respectively.
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Convert the winding measurements to meters by dividing by 39.37 because a meter equals 39.37 inches. Continuing with our example, you now have a length of 3.3 meters and a diameter of 0.0064 meters.
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Divide the diameter by two to calculate the winding wire radius in meters. Radius measures the distance from the center of a circle to its edge. This step in our example yields 0.0064 meters divided by two, or a radius of 0.0032 meters.
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4
Calculate the area of the ends of the windings by multiplying the number pi by the square of the radius. Pi is 3.14. In our example, you multiply 3.14 by 0.0032 meters by 0.0032 meters for an area of 0.000032 square meters.
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Multiply the resistivity of the winding material by the length, then divide by the area, to obtain the resistance in ohms. Assume the windings in this example are made of copper, which has a resistivity of 1.68 times 10^-8 ohm times meter. The symbol "^" represents an exponent and is read as "to the power." Completing the exercise means 1.68 times 10^-8 ohm times 3.3 meters divided by 0.000032 square meters for a resistance of 0.0017 ohms.
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Tips & Warnings
Perform resistance calculations with metric units to avoid calculating the wrong answer.
