ISSN:0002-9505    

DOI:10.1119/1.17106

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.17109

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

In a scattering problem where an incoming particle interacts elastically with more than one scatterer the trajectories that the particle can follow can be quite complex, even in two dimensions. In this paper the elastic scattering of a particle from a two‐disk system is solved explicitly. This is a nontrivial problem that can serve to introduce the concepts needed to understand more complex systems of three or more disks, which defy an explicit analytic treatment. Indeed, a target of more than two disks of equal radius leads to behavior that has recently been termedchaoticscattering.

ISSN:0002-9505    

DOI:10.1119/1.17110

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

An instructive experiment for observing the Leidenfrost phenomenon is presented. The experiment, suitable for an undergraduate experimental course, consists of introducing a copper body at room temperature into liquid nitrogen and observing its temperature history. The experiment is then repeated with the body covered by a thermal insulating material, observing that the body reaches thermal equilibrium much more rapidly in the second case. This apparent paradox greatly motivates the students, who need to understand the different regimes of boiling heat transfer to resolve it. The paper also contains an approximate method to determine the insulator thickness that gives the minimum cooling period.

ISSN:0002-9505    

DOI:10.1119/1.17111

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

The subtleties in the derivation of the retarded Liénard–Wiechert potential for a point charge are stressed by explicitly computing and drawing the retarded shape of a moving sphere. This shape is the effective integration region for the charge density and it is computed, with the aid of the ‘‘information collecting sphere,’’ in the limit of vanishing radius (or, equivalently, from the point of view of a remote observer).

ISSN:0002-9505    

DOI:10.1119/1.17112

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

A simple computer program is presented, well within the capability of sophomore students, which solves the Schrödinger equation for a ‘‘lattice’’ of up to 12 potential wells, and which demonstrates many features important in a discussion of semiconductor physics—energy bands, impurity states, amorphous effects, negative effective mass. The ability to present material like this to students computationally may well have a profound effect on what is taught in future physics curriculums.

ISSN:0002-9505    

DOI:10.1119/1.17113

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

The temperature dependence of the Hall emf under conditions of constant drive potential difference and constant magnetic flux density is obtained for a commercial Hall generator (Honeywell 7SS) having ann‐type Si channel. From the measurements, the temperature dependence of the electron conductivity mobility (μ) and the Hall factor are obtained, with results in good agreement with those of others. Conditions for optimizing the Hall emf per unit magnetic flux density are considered for rectangular bar geometry and are applied to determine an approximate value of μ for electrons in silicon. Room‐temperature transverse magnetoresistance measurements are obtained for the 7SS device and another device having ann‐type Si channel (Sprague 3604). These magnetoresistance measurements are also used for an approximate determination of μ.

ISSN:0002-9505    

DOI:10.1119/1.17114

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

Three methods, none of them widely known, are presented for determining the orbit of a particle subject solely to an inverse‐square central force: One is by Laplace, another by Jacobi; the third may be here making its first appearance in print. All three differ markedly in major thrust; all of them culminate, of course, in conic‐section orbits. Also included is use of a novel integration technique in the execution of a standard textbook solution of the same inverse‐square orbit problem.

ISSN:0002-9505    

DOI:10.1119/1.17115

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

Tuning forks can vibrate in many different modes in which the tines move either in the plane or perpendicular to the plane of the fork. Symmetrical modes can be modeled by the motion of two cantilever beams, antisymmetrical modes by the motion of a beam with free ends. A tuning fork vibrating in its fundamental mode is approximately a linear quadrupole sound source whose strength can be increased by use of a baffle or by touching the stem to a soundboard. The motion of the stem includes strong components at both the fundamental frequency and its second harmonic. Slight alterations in a tuning fork can enhance or suppress either of these components. At large amplitudes, the tines vibrate nonsinusoidally, thenth harmonic increasing approximately as thenth power of the fundamental.

ISSN:0002-9505    

DOI:10.1119/1.17116

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP

摘要:

An experiment was conducted to investigate the effects of cooperative group learning on the problem solving performance of college students in a large introductory physics course. An explicit problem solving strategy was taught in the course, and students practiced using the strategy to solve problems in mixed‐ability cooperative groups. A technique was developed to evaluate students’ problem solving performance and determine the difficulty of context‐rich problems. It was found that better problem solutions emerged through collaboration than were achieved by individuals working alone. The instructional approach improved the problem solving performance of students at all ability levels.

ISSN:0002-9505    

DOI:10.1119/1.17117

出版商:American Association of Physics Teachers    

年代:1992

数据来源: AIP