摘要:

The earliest experiment a student performs when studying electromagnetism is the magnetic field at the center of a flat circular coil carrying an electric current. Later he may study the field at points along the axis of the coil. This paper deals essentially with the measurement of the magnetic field at points along a diameter of the coil, which is not generally attempted. The paper focuses on the usefulness of this laboratory exercise from the standpoints of pedagogy and practical application.

ISSN:0002-9505    

DOI:10.1119/1.15166

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

A systematic frame for the theory of classical physics is presented. The purpose of the modification in structure of the science is to economize the teaching, learning, and application of physics, and the communication with other disciplines. Isomorphic procedures applicable to the branches of physics and to other sciences are recommended. A system is defined as an imagined container; its contents of extensive (substancelike) quantities are used to describe the state of the system; balance equations account for the dynamic change in a system’s state through processes. The procedure, essentially a space integral formulation of macroscopic transport equations, is applied to physics by using the extensive quantity of entropy and the conserved extensive quantities of mass, energy, momentum, angular momentum, and electric charge. Examples are given from the areas of mechanics, electricity, and heat.

ISSN:0002-9505    

DOI:10.1119/1.15167

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

The famous Friis antenna formula relating received power to transmitted power, distance between antennas, wavelength, and antenna areas is derived in the Fraunhofer approximation utilizing the results of single‐slit diffraction theory. Since the original exact formula was derived from Fresnel theory this Fraunhofer treatment improves its accessibility for undergraduates.

ISSN:0002-9505    

DOI:10.1119/1.15168

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

This paper establishes a connection between duality rotations of the electromagnetic field and the relativistic motion of a charged particle. The connection is a mathematical one, yet it helps to make the physics of charged‐particle motions transparent. Explicit forms for the relativistic velocity and the gyration angle in a constant field are given. The result for the gyration angle in both electric and magnetic constant fields is not widely known, and is discussed at some length.

ISSN:0002-9505    

DOI:10.1119/1.15169

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

A flexible counter using Geiger–Muller tubes, appropriate for use in an introductory physics laboratory, is described. The counter has the feature that counts registered in consecutive intervals are easily determined. An experiment that uses this feature is described.

ISSN:0002-9505    

DOI:10.1119/1.15170

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

The problem of Maxwell’s sorting demon traditionally has been studied for the case in which the hot and cold regions differ very little in temperature. In this article a solution is presented for the case in which the temperature difference is great so that the total entropy is lower. Calculations indicate that in this case the demon must use a large number of photons to observe the proper kinds of particles. This causes an increase in entropy which more than offsets the decrease caused by an exchange of particles.

ISSN:0002-9505    

DOI:10.1119/1.15171

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

We define, in analogy to electrodynamics, the gravitational Poynting vector and show that it provides a mechanism for the transfer of gravitational energy to a system of falling objects.

ISSN:0002-9505    

DOI:10.1119/1.15172

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

The energy spectrum of Lorentz invariant radiation is deduced by taking explicit account of the Doppler effect and aberration. A general formula, valid fornspatial dimensions is found.

ISSN:0002-9505    

DOI:10.1119/1.15173

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

摘要:

The measurement of the higher levels of 63P2and 61P1of the mercury atom in the Franck–Hertz experiment has been introduced into the junior and senior laboratory course by using a homemade tetrode Franck–Hertz tube. The main structure of the tube is described. The optimum operating conditions are in the temperature range between 130 and 150 °C and the collector currents are of the order of 10−9A. The additional observations of the famous Franck–Hertz experiment in the laboratory course will give the students more familiarity with the quantum behavior of atoms.

ISSN:0002-9505    

DOI:10.1119/1.15174

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.15149

出版商:American Association of Physics Teachers    

年代:1987

数据来源: AIP