摘要:

Many misleading or incorrect explanations of tape recorder bias have appeared in trade journals and popular magazines. These explanations, which tend to ignore magnetic hysteresis, are particularly confusing to physics students. A brief discussion of bias and its effect on recorded magnetization is presented, along with several references to reliable sources for further reading on the subject.

ISSN:0002-9505    

DOI:10.1119/1.12441

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

In 1583, Joseph Justus Scaliger introduced the Julian Period of 7980 years, which is the basis of the Julian Day system of counting days sequentially from 1 January 4713 BC. It is not commonly known how this date was chosen as the origin of the system. This paper formulates the problem as an application of the theory of congruences and the Chinese Remainder Theorem. Scaliger’s interesting original solution to the problem is also reviewed.

ISSN:0002-9505    

DOI:10.1119/1.12442

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

Infinite cylinders composed of polytropic material can possess nearly arbitrary rotation fields while retaining the fundamental simplicity of one‐dimensional structures. The physical properties of these objects can be easily calculated and understood by junior–senior level physics students even without access to a large computing facility. Analytical results are presented here for polytropic index 0 and 1 as well as numerical results for polytropic index 1.5.

ISSN:0002-9505    

DOI:10.1119/1.12454

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

A simple method is presented to solve the Korteweg–de Vries equation. If one assumes that the solution can be written as a product of two functions, it is shown that each of them can be related to the same Schrödinger equation. The well‐known multisoliton solution then appears in a convenient way, if one deals with discrete eigenvalues.

ISSN:0002-9505    

DOI:10.1119/1.12422

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

Recently Schmid has derived an explicit representation of the permutation operator in terms of coordinate and momentum operators expressed as an infinite series. Here we give an alternative derivation yielding a closed expression ? = exp(i?), which in several respects is more satisfactory.

ISSN:0002-9505    

DOI:10.1119/1.12423

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

An application of solid‐state memories in a laboratory course is described which can achieve a two‐fold goal. First, it enables students to build devices that are commercially sold at much higher prices; second, it offers an opportunity to introduce the fundamentals of analog‐to‐digital conversion and sampling theory in a very practical way. Both aspects are discussed.

ISSN:0002-9505    

DOI:10.1119/1.12424

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

Simple method for bandstructure calculations is presented to bridge the gap between textbook treatments and research calculations. The method is based on the multiple scattering of electrons in periodic potentials and can be applied in a straighforward way to obtain the essential features of electronic bandstructures in one, two, and three dimensions. In the one‐dimensional case the method is applied to the Kronig–Penney model and the results compared with other methods. Extensions to two and three dimensions are also presented.

ISSN:0002-9505    

DOI:10.1119/1.12425

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

The production of work from a heat source with finite heat capacity is discussed. We examine the conversion of heat from such a source first by a single Carnot engine and then by a sequence of Carnot engines. The optimum values of the operating temperatures of these engines are calculated. The work production and efficiency of a sequence with an arbitrary number of engines is derived, and it is shown that the maximum available work can be extracted only when the number of cycles in the sequence becomes infinite. The results illustrate the importance of recovery or bottoming processes in the optimization of work‐producing systems. In addition, the present model illuminates one practical limitation of the Carnot cycle: The Carnot efficiency is only obtainable from a heat source with infinite heat capacity. However, another cycle, somewhat reminiscent of the Otto and Brayton cycles, is derived which will provide the maximum efficiency for a heat source with a finite heat capacity.

ISSN:0002-9505    

DOI:10.1119/1.12426

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

The problem of changing direction with limited acceleration in the least amount of time is considered. The quickest turn is shown to be the one which minimizes the path length in velocity‐space under the given constraints. The problem where initial and final conditions are symmetric is examined in some detail.

ISSN:0002-9505    

DOI:10.1119/1.12427

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP

摘要:

The authors point out that the inertial force F3= −mω×r is completely analogous to the force associated with an induced emf. (AIP)

ISSN:0002-9505    

DOI:10.1119/1.12428

出版商:American Association of Physics Teachers    

年代:1981

数据来源: AIP