SELF

74

S.B. Karavashkin and O.N. Karavashkina

Experimental study of electromotive force induced by inhomogeneous magnetic field

Sergey B. Karavashkin and Olga N. Karavashkina

Special Laboratory for Fundamental Elaboration SELF

187 apt., 38 bldg., Prospect Gagarina, Kharkov 61140, Ukraine

phone: +38 (057) 7370624

e-mail: selftrans@yandex.ru , selflab@mail.ru

We will consider two formulations of induction law: differential, based on Faraday conception of wire interaction with magnetic field, and integral, based on Maxwell conception of interaction of the loop area with the crossing flux.

Using the models of rectilinear loop with a movable side and of unipolar generator, we will show that Maxwell conception remains true exceptionally for the loop with a movable side. Only for such model this formulation predicts the same results as Faraday formulation does. At the same time, Faraday formulation is true both mathematically and phenomenologically for a broad class of models in homogeneous and inhomogeneous magnetic fields.

To check it experimentally, we developed a set with the transforming secondary loop and put it into an inhomogeneous time-variable magnetic field. Obtained experimental results will unambiguously corroborate that Faraday conception reliably describes the induction process on the basis of wire interaction with magnetic field, and that Maxwell integral conception is illegal.

Obtained experimental results have also corroborated that it is legal to use the compensation loop with a single probe in studying the local magnetic fields, which we used in the before study of induction in an air gap of transformer.

Keywords: electromagnetic theory, dynamical magnetic field, dynamical electric field, electromagnetic induction, electromagnetic induction, induction in a single conductor

Classification by PASC 2001: 03.50.-z; 03.50.De; 41.20.Gz; 85.30.Tv; 85.70.-w; 85.70.Ay; 85.80.Jm.

Introduction

Before, in [1], we studied electromotive force (emf) induced in a single wire and in this study used as a probe a compensative loop (see Fig. 1 that replicates Fig. 12, page 79 of [1]), whose central rod was located in the studied magnetic gap.

Fig. 1. General appearance of compensative loop for studying the emf induced by time-variable magnetic field in a single wire AB

Multiple discussions followed that publication at physical forums and showed that for some colleagues the possibility of excitation of parasitic emf in the tapping wires of loop and its influence on the experimental indications seems not enough substantiated.

The cause of colleagues' doubt was that the issue of parasitic emfs in tapping wires is connected with another, no less important problem - the old-rooted idea that we have to calculate the induction emf excited by a time-variable magnetic field by way of integrating over the area of secondary loop.

This difficulty is complicated for resolving because, on one hand, when measuring the induced emf, we always make a secondary loop. On the other, the emf distribution along the wire of secondary loop in inhomogeneous magnetic field never was checked - or these studies and their technique never were published. No one drew an attention to these features, the more that it is practically impossible to tune away from the tapping wires. This problem became topical when the emf in a single wire has been studied, as the issues, whether it is legal to find the emf, integrating over the loop area, and whether the phenomenology of the induction process and, finally, the integral form of Maxwell equations are legal, highly depend on its solution.

In this paper we will present the results of study which corroborates that the induction along the wire of secondary loop within an inhomogeneous magnetic field is not uniform. This study will refine the phenomenology of induction process in time-variable magnetic fields and will permit us to substantiate additionally, how much legal is it - to use the compensative loop in measuring the emf induced in local time-variable magnetic field.