pISSN 0374-4914 eISSN 2289-0041

## Research Paper

New Phys.: Sae Mulli 2021; 71: 383-389

Published online April 30, 2021 https://doi.org/10.3938/NPSM.71.383

## Scientific Inquiry Activity to Measure the Conductivity of a Conductor by Using Magnetic Levitation

Sungwook HONG*

Division of Science Education, Daegu University, Gyeongsan 38453, Korea

Correspondence to:swhong@daegu.ac.kr

Received: January 7, 2021; Revised: February 3, 2021; Accepted: February 16, 2021

### Abstract

In this study, the forces on a permanent magnet near a vertically rotating Cu plate were analyzed, and a method of measuring the conductivity of a conductor, such as Cu, was devised. The magnetic levitation force, $F_{L}$, and the drag force, $F_{D}$, act spontaneously on the magnet. $F_{L}$ and $F_{D}$ were determined by using a pendulum, that was designed to restrict the degree of freedom of one of the two angles to measure two angles in dividually. When the distance between the Cu surface and the magnet was constant, the higher the rotational linear velocity of Cu was, the greater the $F_{D}$ was. However, when the linear velocity was constant, $F_{D}$ was inversely proportional to the square of the distance. Because the distance increased when the linear velocity of the Cu plate increased, the magnetic levitation force $F_{L}$ can be expressed as a function of the velocity and the distance. $F_{D}$ decreased with decreasing linear velocity of Cu when measured under the same measurement conditions as $F_{L}$, and the conductivity of Cu was found to be $\sigma = 5.92 \pm 0.35 \times 10^{7} \Omega^{-1}$m$^{-1}$ based on the relationship between $F_{L}$ and $F_{D}$.

Keywords: Division of Science Education, Daegu University, Gyeongsan 38453, Korea