An improved parallel-plate capacitor apparatus for the estimation of dielectric constants of solid materials

摘要

In this paper, we present the design and implementation of a modified parallel-plate capacitor (PPC) and its mathematical derivation, which may well be incorporated as a challenging problem in physics textbooks covering topics on capacitance and dielectrics. The dielectric material under test (MUT) fills the empty space between the plates of the PPC, and a very thin layer of air is trapped between the uneven surfaces of the metallic capacitor plates and the MUT. It has been reported in the literature (Grove T T et al 2005 Am. J. Phys. 73 52-56; Grove T T and Masters M F 2009 The Physics Teacher 47 312) that these air pockets lead to an error in the measured value of the dielectric constant of the MUT. The present work gives a prescription to estimate this value in a smart way so as to bypass the effect of a trapped thin air layer, and it leads to measured values of the dielectric constant similar to what has been reported in the literature (PLEXIGLAS (R), Altuglas International and Arkema Inc., 2006 www.altuglasint.com ). To the best of our knowledge, this paper is the first to present the design and implementation of a PPC cell of this kind to study dielectric constants. The topic can reasonably be taught in undergraduate laboratory physics coursework.