ISSN:0002-9505    

DOI:10.1119/1.16238

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.16241

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.16242

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

摘要:

It is demonstrated that the premisses of the Einstein–Podolsky–Rosen paper are inconsistent when applied to quantum systems consisting of at least three particles. The demonstration reveals that the EPR program contradicts quantum mechanics even for the cases of perfect correlations. By perfect correlations is meant arrangements by which the result of the measurement on one particle can be predicted with certainty given the outcomes of measurements on the other particles of the system. This incompatibility with quantum mechanics is stronger than the one previously revealed for two‐particle systems by Bell’s inequality, where no contradiction arises at the level of perfect correlations. Both spin‐correlation and multiparticle interferometry examples are given of suitable three‐ and four‐particle arrangements, both at the gedanken and at the real experiment level.

ISSN:0002-9505    

DOI:10.1119/1.16243

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

摘要:

Following the Fresnel theory of light and the consequent scientific debate that his formulation generated, two key experiments with electrons, diffraction by means of a circular hole and a circular obstruction, have been realized to show the existence of the Fresnel zones and of the so‐called ‘‘Poisson spot.’’ The basic arguments concerning the quantum mechanical nature of electrons can be introduced by taking advantage of the vivid impression stimulated by the experimental images.

ISSN:0002-9505    

DOI:10.1119/1.16489

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

摘要:

This paper develops the argument, presented briefly by Lindhard in 1953, that a perfectly conducting metallic sample is unable to keep out a steady magnetic field, since even in the absence of collisions the field energy can still be reduced by transfer to the electron assembly. For a plane slab the analysis, which is given in detail, is an extension of the theory of the anomalous skin effect, and the ineffectiveness concept plays the same role in elucidating the physical mechanism. In samples of other shapes, interaction with the field may not be so narrowly confined to a small fraction of effective electrons, but it is suggested that the diffusion of magnetic field nevertheless proceeds at a rate that is usually rather indifferent to shape.

ISSN:0002-9505    

DOI:10.1119/1.16244

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

摘要:

Compressional, torsional, and bending waves in bars and plates can be studied with simple apparatus in the laboratory. Although compressional and torsional waves show little or no dispersion, bending waves propagate at a speed proportional to (f)1/2. Reflections at boundaries lead to standing waves that determine the vibrational mode shapes and mode frequencies. Boundary conditions include free edges, simply supported edges, and clamped edges. Typical mode shapes and mode frequencies for rectangular bars, circular plates, and square plates are described.

ISSN:0002-9505    

DOI:10.1119/1.16245

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

摘要:

A relatively simple method is presented that has been used in an undergraduate experimental course for observing the superfluid transition in4He. The experimental technique consists of submerging a vibrating reed in liquid helium and observing the changes in frequency and damping (energy dissipation) as the temperature is regulated above and below the superfluid transition. The results of the measurements are interpreted by means of a simplification of the acting hydrodynamic forces, and it is seen that most of the relevant physics is well described by the approximations.

ISSN:0002-9505    

DOI:10.1119/1.16246

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

摘要:

From the perspective of Ampere’s circuital law, either displacement current or conduction current can be viewed as the source for the magnetic field inside a circular capacitor that is slowly being charged. The Biot–Savart law is more selective. How it can be used with conduction current alone is shown. Also considered is the ‘‘leaky capacitor. Here it is shown that an isolated charged capacitor which discharges slowly in a homogeneous Ohmic dielectric produces no magnetic field anywhere. Alternatively, a field is produced if the conducting material is confined to a limited region. This field is calculated for a circular capacitor when only the material in the gap is conducting.

ISSN:0002-9505    

DOI:10.1119/1.16247

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP

摘要:

The Coriolis force on a particle (acting within a rotating frame) and the magnetic force on a charge, are both proportional to and act perpendicular to the velocity. As a consequence, the action of the Coriolis force on rotating mass, and the action of the magnetic force on rotating charge are formally identical. Just as the action of a magnetic field is to align the axis of the rotating charge distribution (magnetic dipole) with itself, so the Coriolis force aligns the axis of a rotating mass distribution (angular momentum) with the angular velocity of the rotating frame. This enables us to understand the gyrocompass by analogy with the magnetic compass. A simple way to demonstrate the gyrocompass to a class is also presented.

ISSN:0002-9505    

DOI:10.1119/1.16498

出版商:American Association of Physics Teachers    

年代:1990

数据来源: AIP