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As we all know, the copper used in the production of wires and cables requires pure copper (purity is generally 99.9% ~ 99.95%), and the conductivity of pure copper is certain. Therefore, in the production process of copper wires, the wire diameter can be guaranteed by controlling the resistance, and the resistance can also be guaranteed by controlling the wire diameter. So, is it easy to control the resistance or the wire diameter? This depends on the specific situation.

Let's take a look at the wire diameters and resistance ranges of the two specifications. According to IEC standard, the diameter range of 0.020 copper wire is 0.0192 ~ 00208mm; The diameter range of 0.100 copper wire is 0.097 ~ 0.103mm. According to physical knowledge, the resistance of a wire is directly proportional to the conductivity and length of the wire, and inversely proportional to the square of the cross-sectional area of the wire. We can find that the meter resistance range of 0.020 specification copper bare wire is 52.561 ~ 61.686 ohms; The meter resistance range of 0.100 copper bare wire is 2.143 ~ 2.417 ohms.

From the wire diameter range and resistance range of the above two specifications, we can see that the wire diameter tolerance of the 0.020 specification is 0.0016mm, and the resistance tolerance is 9.125 ohm, while the wire diameter tolerance of the 0.100 specification is 0.006 mm, and the resistance tolerance is 0.274 ohm. That is to say, if the wire diameter of 0.020 fluctuates by 0.0016 mm, the resistance will fluctuate by 9.125 ohms, while if the wire diameter of 0.100 fluctuates by 0.006 mm, the resistance will fluctuate by only 0.274 ohms. Take the 0.020 specification line as an example. 9.125 ohm corresponds to 0.0016 ohm, that is, 1 ohm only corresponds to 0.000175 mm, ohm, and the wire diameter hardly changes. The resistance of 1 ohm is not only easy to measure but also easy to control. However, it is not so easy to measure 0000175mm and be controlled. Therefore, for ultra-fine wires, it is easy, convenient and scientific to control the resistance or wire diameter by measuring the resistance because of the large resistance range, convenient measurement and easy control. For thick wires, on the contrary, it is easy, convenient and scientific to control the right resistance of the wire diameter by measuring the wire diameter Science.

f measuring the wire diameter is used to control the wire diameter or resistance for ultra-fine wires, and measuring the resistance is used to control the resistance or wire diameter for thick wires; It is also unscientific. Because the allowable fluctuation range is narrow, it is difficult to measure and control, and the existence of measurement error makes it more difficult to ensure the wire diameter and resistance.

To sum up, as long as the out of roundness of the bare wire meets the requirements, the resistance or wire diameter of the bare wire should be controlled by measuring the resistance in the production of ultra-fine enameled wire; In the production of general fine enameled wire, the measurement of bare wire can not only control the resistance or wire diameter by measuring the resistance, but also control the wire diameter and resistance by measuring the wire diameter; In the production of enameled wire, the wire diameter or resistance should be controlled by measuring the wire diameter; In the production of rough enameled wire, the wire diameter or resistance should be controlled by measuring the wire diameter. Only in this way can it be easy, convenient and scientific.