摘要:

The need for a strict definition of fundamental units of measurement is pointed out. The fact that the ampere is defined by an equation in terms of other previously defined quantities requires that it be defined in terms of those quantities. This would give the ampere the unit ofnewton12, and would make the permeability unitless. The instructional value of this analysis is pointed out by showing the ease with which the undergraduate student may balance, dimensionally, equations involving electrical quantities.

ISSN:0002-9505    

DOI:10.1119/1.1933903

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

An attempt has been made to convert laboratory performance tests into essay and multiple-choice items. Preliminary forms of the tests were administered to about 160 elementary physics students. It was found that the multiple-choice was the least difficult of the three tests; the performance, the most difficult. The correlation coefficients between relatively complex performance items and their paper-pencil analogs were very low. The correlations between the items dealing with specific skills and parallel paper-pencil tests were low to moderate. The preliminary study supports the hypothesis that paper-pencil tests are poor substitutes for performance examinations.

ISSN:0002-9505    

DOI:10.1119/1.1933904

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

Filtered pulsating light from a mercury vapor lamp operated on ac is directed upon a commercial high-vacuum phototube, and the photocurrent, which is thereby pulsating dc, is passed by an ac amplifier whose output is fed to a dc milliammeter through a copper oxide rectifier. Using different light filters a retarding potential of increasing magnitude is applied to the phototube until the milliammeter readings reach respective minimum values which are plotted as ordinate against optical frequency as abscissa. The slope of the resulting line is taken ash/e.

ISSN:0002-9505    

DOI:10.1119/1.1933905

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

An experiment in single dimensional heat flow suitable for an intermediate laboratory course is described.

ISSN:0002-9505    

DOI:10.1119/1.1933906

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

The desirability and the difficulty of retrieving modern scientific concepts in classical scientific authors is discussed with particular reference to a recently published re-evaluation of Sadi Carnot's memoir. Evidence is presented to support the interpretation of Carnot provided by his nineteenth-century successors and current in modern texts: Carnot's use of the material theory of heat led him to misconstrue the foundations of thermodynamics, but the misconstruction, discoverable only in retrospect, is irrelevant to his stature as a profound and original investigator.

ISSN:0002-9505    

DOI:10.1119/1.1933907

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

New evidence is presented from Carnot's memoir to show that he defined “calorique” (entropy) differently from “chaleur” (heat in the general sense). Calorique is the thermal quantity conserved in reversible cycles; the unit of calorique melts one kilogram of ice; the unit of chaleur raises the temperature of a kilogram of water one degree centigrade, an irreversible process.Although Carnot used these terms interchangeably for constant temperature (reversible) processes, which is justified when the temperature scale is not specified, he distinguished between chaleur and calorique for work producing reversible processes operating over a finite temperature range, where the distinction becomes necessary.Carnot's major conclusions onheatengines are deduced on general principles and are not dependent upon any caloric or mechanical theory of heat. Carnot believed in the mechanical theory of heat, but in the last parts of the memoir he introduced, as axioms, conservation theorems for calorique (correctly) and for chaleur (incorrectly) which have tenets in common with the now-discredited caloric theory. These theorems do not require that these quantities be substantive in nature.

ISSN:0002-9505    

DOI:10.1119/1.1933908

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

Although Carnot's contributions to thermodynamics have been universally recognized, it is usually with the reservation that there were serious gaps in his proof. Careful study of his memoir shows that Carnot implicitly defined heat so as to make it equivalent to entropy. With this interpretation it may be shown that his logic was flawless, that he believed in the kinetic nature of heat, and that his theorems are based on the first and second laws of thermodynamics.

ISSN:0002-9505    

DOI:10.1119/1.1933909

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

The two distinct ways in which a current may be carried by ann-type semiconductor—by electrons and by “holes”—are illustrated by means of a model. It is the control of one type of current by the other which makes possible various forms of transistor action.

ISSN:0002-9505    

DOI:10.1119/1.1933910

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

An experiment at the undergraduate level to study various nuclear radiations by utilizing a beta-ray spectrograph is outlined. A relativistic treatment of the data obtained allows a straightforward interpretation, while a classical analysis fails. This proves to be a simple way to demonstrate the use of relativistic energy and momentum equations to the student.

ISSN:0002-9505    

DOI:10.1119/1.1933911

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

The one-dimensional rectangular potential well problem is one of the standard examples used in courses to illustrate quantum-mechanical properties. It has also been of value in the study of nuclear energy states. However, it is necessary to resort to graphical or numerical procedures at the last if one desires explicit values for the energy levels. It is the purpose of this article to point out a simpler and more perspicuous method of graphical solution than those used at the present time.

ISSN:0002-9505    

DOI:10.1119/1.1933912

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP