ISSN:0002-9505    

DOI:10.1119/1.12088

出版商:American Association of Physics Teachers    

年代:1980

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.12089

出版商:American Association of Physics Teachers    

年代:1980

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.12091

出版商:American Association of Physics Teachers    

年代:1980

数据来源: AIP

摘要:

Students in a junior‐level thermodynamics course were presented a practical problem in which a human body must maintain its normal interior temperature of 37 °C while the surface is at 15 °C. Suggested solutions to this problem are offered along with details of heat flow in the body.

ISSN:0002-9505    

DOI:10.1119/1.12092

出版商:American Association of Physics Teachers    

年代:1980

数据来源: AIP

摘要:

A pulsed x‐ray tube is used to generate Poisson distributions. By varying the tube plate current, we produce distributions with different mean, and show the transition to Gaussian form as the mean increases. The relationship of these distributions to electronic ’’shot noise’’ is discussed.

ISSN:0002-9505    

DOI:10.1119/1.12105

出版商:American Association of Physics Teachers    

年代:1980

数据来源: AIP

摘要:

Three simple distinct operational procedures are given for transforming the empirical notion of speed into a formal concept. While in the Galilean theory of space‐time, the three quantities coincide with the customary velocity, they differ in the Einsteinian theory. In particular, it is shown that ’’rapidity’’ has a direct and natural physical meaning.

ISSN:0002-9505    

DOI:10.1119/1.12093

出版商:American Association of Physics Teachers    

年代:1980

数据来源: AIP

摘要:

The Lagrangian for a single classical charged particle is made form invariant under the addition of a total time derivative by adding an interaction Lagrangian which involves compensating fields. The compensating fields are the vector and scalar potentials of the electromagnetic field which couple to the current and charge densities, respectively. To insure form invariance of the Lagrangian, the vector and scalar potentials must undergo the usual gauge transformations of electromagnetism. The electric and magnetic fields, which are gauge invariant, are obtained by examining the equation of motion for the charged particle. Faraday’s law and the condition that there are no magnetic monopoles are obtained from the expressions for the electric and magnetic fields in terms of the potentials. The simplest possible gauge‐invariant Lagrangian which is quadratic in the electric and magnetic fields is constructed. From the principle of least action Gauss’ law and the Ampère–Maxwell law are obtained.

ISSN:0002-9505    

DOI:10.1119/1.12094

出版商:American Association of Physics Teachers    

年代:1980

数据来源: AIP

摘要:

A diffusional driving force, called the radial force, which is responsible for the increase with time of the scalar separation between a fixed point and a particle undergoing three‐dimensional Brownian motion, is derived using Boltzmann’s equation. The radial force is used to derive several results from the classical theory of Brownian motion, namely Einstein’s 〈x2〉 = 2Dtequation and the expression for the one‐dimensional harmonic oscillator. The radial force concept is then extended to establish a thermodynamic criterion for the occurrence of a melting transition in a liquid whose particles attract one another by means of centrally symmetric forces. The theory, when applied to the alkali halide and alkaline‐earth oxide molten salts, accurately predicts the observed melting temperatures. The definition of the dielectric constant used in the ionic salt fusion theory also provides a basis for understanding molten salt surface tensions. Finally, the radial force is used to demonstrate that an ideal rubber network is not prone to collapse into a state having zero volume.

ISSN:0002-9505    

DOI:10.1119/1.12095

出版商:American Association of Physics Teachers    

年代:1980

数据来源: AIP

摘要:

An experimental setup is described which will allow one to study the resonance characteristics of a vibrating plate. One can determine the resonance frequency, damping coefficient, and quality factor, obtain the resonance curve, measure the vibration amplitude, and demonstrate nonlinear behavior. The methods are demonstrated using a small, circular steel plate clamped around its periphery. Much of the output is obtained graphically, which should enable the student to gain a more thorough understanding of the phenomena.

ISSN:0002-9505    

DOI:10.1119/1.12096

出版商:American Association of Physics Teachers    

年代:1980

数据来源: AIP

摘要:

When a vertical, vibrating string is silhouetted against a television screen, a wavelike shape may be seen. The shape will appear distinct and stationary if the ratio of the string’s fundamental frequency to 60 Hz is the ratio of small integers. The vertical scan of the (horizontally sweeping) electron beam is responsible for this shape, which amounts to a displacement versus time graph for the string. The effect can be used to tune stringed musical instruments to absolute pitch.

ISSN:0002-9505    

DOI:10.1119/1.12097

出版商:American Association of Physics Teachers    

年代:1980

数据来源: AIP