摘要:

A brief account is given of the teaching activities of Professor J. C. Jensen of Nebraska Wesleyan University during the last forty-five years. The story demonstrates how much can be accomplished with small financial resources if the teacher possesses energy, enthusiasm, and a lively interest in young people.

ISSN:0002-9505    

DOI:10.1119/1.1934163

出版商:American Association of Physics Teachers    

年代:1956

数据来源: AIP

摘要:

The principles underlying the extension of the Maxwell equationcurlE = −∂B/∂tto moving media are discussed, and illustrations with specific moving systems are presented. The principles are applied to the case of the unipolar generator.

ISSN:0002-9505    

DOI:10.1119/1.1934165

出版商:American Association of Physics Teachers    

年代:1956

数据来源: AIP

摘要:

The magnetostatic field due to an elliptic cylinder carrying steady current in a nonuniform magnetic field is determined through the use of magnetic vector potentials and complex potential functions. The resultant force and couple on the cylinder are deduced and their forms investigated in the particular cases when (i) the cylinder is of circular section, and (ii) when the external magnetic field possesses a certain type of symmetry.

ISSN:0002-9505    

DOI:10.1119/1.1934166

出版商:American Association of Physics Teachers    

年代:1956

数据来源: AIP

摘要:

A series of measurements of the propagation of sound in liquid helium are described, and the results discussed in terms of various aspects of the theory of liquid helium. Measurements of the velocity were first made at 14.2 mc/sec over the temperature range from the normal boiling point down to 1.2°K, with particular attention to the low-temperature region and the neighborhood of the λ point. The attenuation was later measured at 2.0, 6.0, and 12.1 mc/sec, and the measurements were extended down to 0.85°K. A few velocity measurements were also made at these frequencies. Finally the 12.1 mc/sec results were extended down to 0.1°K by the technique of adiabatic demagnetization. The attenuation in helium II is anomalously high and passes through two closely spaced maxima a little below 1°K, finally falling smoothly toward zero at the absolute zero. No adequate theoretical explanation for this behavior exists, although above 1°K the high attenuation has been explained qualitatively. Near the λ point the attenuation rises to another very sharp maximum and the velocity passes through a minimum. This behavior sheds some light on the nature of the λ transition. The first part of this paper is devoted to a brief review of relevant experimental and theoretical aspects of the liquid helium problem.

ISSN:0002-9505    

DOI:10.1119/1.1934167

出版商:American Association of Physics Teachers    

年代:1956

数据来源: AIP

摘要:

The small number of physicists in training is a matter of national concern. The quality of the teaching of physics and the attention given the undergraduate students are here considered as factors contributing to the present difficulties.

ISSN:0002-9505    

DOI:10.1119/1.1934168

出版商:American Association of Physics Teachers    

年代:1956

数据来源: AIP

摘要:

This paper is an attempt to improve greatly the consistency of delta-ray counting along tracks of heavy nuclei in emulsions. The problem is complicated and, unless satisfactory criteria are properly followed, variable results may be expected both from a given scanner and from different scanners. A set of criteria are given. Considerable information regarding their use is included. This work is adapted to nuclei withZ's of ten or greater.

ISSN:0002-9505    

DOI:10.1119/1.1934169

出版商:American Association of Physics Teachers    

年代:1956

数据来源: AIP

摘要:

Small portable clocks were in use at the end of the fifteenth century. Three interesting paintings now hanging in European galleries are here reproduced and the possibility that they portray such clocks is discussed.

ISSN:0002-9505    

DOI:10.1119/1.1934170

出版商:American Association of Physics Teachers    

年代:1956

数据来源: AIP

摘要:

The mks system of units is explained and compared with the Gaussian system (and its components, the cgs electrostatic system and cgs electromagnetic system). It is suggested that the mks system is the easier system to use. Symbols, dimensions, units, and equivalents are given for the most important electric and magnetic quantities. Many of the more common equations are written in both systems, and a simple scheme for conversion is presented.

ISSN:0002-9505    

DOI:10.1119/1.1934171

出版商:American Association of Physics Teachers    

年代:1956

数据来源: AIP

摘要:

Apparatus consisting of two precision potential dividers, a student's galvanometer, a cheap standard cell, a table radio receiver, and a pair of intermediate frequency transformers is shown to be sufficiently flexible and sufficiently precise to allow it to be used for a large part of the electrical calibrations needed in a laboratory. Accuracies of about14of 1% at zero frequency and of about 1% at 455 kilocycles per second can be obtained. The total cost of the equipment is $125 or less.

ISSN:0002-9505    

DOI:10.1119/1.1934172

出版商:American Association of Physics Teachers    

年代:1956

数据来源: AIP

摘要:

A method of determining from a vector diagram the inductive reactance of an inductor in terms of the circuit constants and for determining the capacitive reactance of a capacitor also in terms of circuit constants is explained. The plan is to consider a uniform circular motion point in its path around a circle of a properly chosen dimension radius vector and to compare the speed of the uniform circular motion point with the speed of its simple harmonic projection point moving along the vertical axis.

ISSN:0002-9505    

DOI:10.1119/1.1934173

出版商:American Association of Physics Teachers    

年代:1956

数据来源: AIP