Use of a current balance to calibrate an ammeter and to determine the magnetic permeability of free space

摘要

This paper describes a laboratory experiment using a current balance to check the calibration of an ammeter and to determine the magnetic permeability of free space. The current balance measures current by measuring the force between two parallel wires carrying that current. The results of each of the experiments are reported, and comparisons with theoretical predictions are included. The slope of ammeter reading versus measured current should be 1 and the intercept zero. The experimental values were 0.989 with an intercept of 0.25 and 1.008 with an intercept of 0.065 for current ranges from 2 to 15 A and 5 to 15 A, respectively. The calculated magnetic free space was 4.056 pi x 10(-7) N A(-2) and the difference between theoretical and experimental values was 1.4%.