摘要:

An elementary treatment of the dynamical aspects of light refraction and Čerenkov radiation is given. Although some authors have given preference to the Minkowski energy momentum tensor in the interpretation of these effects, the treatment presented here shows that the rival theory of Abraham is fully capable of describing them correctly. A crucial point for the settlement of the old polemic concerning the energy momentum tensors of Abraham and of Minkowski, is recognized to be the existence of the Lorentz force acting on polarization currents. The Abraham energy momentum tensor yields an adequate expression containing this type of force, but the Minkowski one fails to describe this phenomenon.

ISSN:0002-9505    

DOI:10.1119/1.1935095

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

The current-voltage characteristic of a lightbulb can be analyzed graphically to reveal much about heat loss from a hot filament. The low-temperature region is particularly interesting. The experiment can be done and the effects understood by elementary students.

ISSN:0002-9505    

DOI:10.1119/1.1935096

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

Some recent developments in the theory of superconductivity are discussed with emphasis on the underlying physical ideas. It is proposed that the electron-phonon interaction produces a strong preference for singlet zero momentum pairs in two-body correlations which can account for superconductivity and related phenomena.

ISSN:0002-9505    

DOI:10.1119/1.1935097

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

The mysterious demonstration experiment involving a linear array of elastic spheres is discussed. An approach is suggested which permits a sophomore to compute a predicted result, both for the simple case where masses are equal and the number of emerging balls is equal to the number of incident balls, and for the more complicated case of unequal masses where the balls donotknow how to count.

ISSN:0002-9505    

DOI:10.1119/1.1935067

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.1935068

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

This paper considers the parametric excitation of a pendulum swinging in a horizontal plane. It is shown that there exist a number of different limit cycle motions, one of which is a steady rotation about the point of support. This motion is associated with the mechanism whereby a Hula-Hoop may be kept in rotation by an oscillatory motion of the point of support. The stability and dependence of this type of motion on the initial conditions are analyzed in detail.

ISSN:0002-9505    

DOI:10.1119/1.1935069

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

The problem considered is that of rectilinear motion with variable velocity. The paper gives, by an elementary construction, a system of coordinates which is conformal in a restricted region near the axis of the motion. In such coordinates the velocity of light remains invariant even for observers moving with variable velocity. By a particular choice of the scale relation the restricted conformal transformations can be made to reduce to the Lorentz transformation everywhere in the case of constant velocity and locally in the case of variable velocity.

ISSN:0002-9505    

DOI:10.1119/1.1935070

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

Electric potential fields were plotted by means of field mapping paper and probes. The paper was cut into different patterns simulating various electrical circuits. The results present to the student a striking illustration of the potential distributions in these circuits.

ISSN:0002-9505    

DOI:10.1119/1.1935071

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

Exact solutions of the time-dependent wave equation are given for the one-dimensional motion of a particle acted on by an external force and for a forced oscillator. The solutions chosen correspond to the same time dependence for the classical momentum and for the quantum-mechanical space average of the momentum.

ISSN:0002-9505    

DOI:10.1119/1.1935072

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP

摘要:

The three-dimensional angular momentum operatorJtakes a simple form when the operand is a scalar functionf(ξ,η)of the two complex variablesξ,η; so do the angular momentum eigen-statesfmi(ξ,η). Exploitation of this circumstance leads to a simple derivation of Racah's formula for the Clebsch-Gordan (vector addition) coefficients.

ISSN:0002-9505    

DOI:10.1119/1.1935073

出版商:American Association of Physics Teachers    

年代:1960

数据来源: AIP