摘要:

During the year 1969 there are major anniversaries of the birth or death of six men whose accomplishments and influence have been of importance to the development of physics. They are: Armand Hippolyte Louis Fizeau, Thomas Graham, Ernest Fox Nichols, George Gabriel Stokes, James Watt, and Charles Thomson Rees Wilson. Brief accounts of their achievements and lives are given here.

ISSN:0002-9505    

DOI:10.1119/1.1975400

出版商:American Association of Physics Teachers    

年代:1969

数据来源: AIP

摘要:

Lithium-drifted germanium detectors may be profitably used in a variety of experiments in undergraduate physics laboratories. We have attempted to assemble from literature and our own experience an introduction to these devices. Included are some basic experiments relating to the properties of the detectors which are interesting in themselves, but also practical in terms of routine-detector and electronic-system evaluation.

ISSN:0002-9505    

DOI:10.1119/1.1975388

出版商:American Association of Physics Teachers    

年代:1969

数据来源: AIP

摘要:

The well-known inequalityL1L2 ≥ M2connecting the coefficients of self- and mutual inductances for a pair of coupled circuits is derived by analytical methods, and a discussion is given concerning their connection with the physical arguments found in elementary textbooks.

ISSN:0002-9505    

DOI:10.1119/1.1975390

出版商:American Association of Physics Teachers    

年代:1969

数据来源: AIP

摘要:

Because of the short charge relaxation time for water, an electrostatic solution for conductors usually applies. But to extend the analysis to very short interaction times, a solution is derived for the electrostatic field strength and force acting on a nonconducting dielectric sphere near a grounded conducting plane. This solution has more general interest, since it is one of the relatively few that are exact and apply to a physically realizable geometry.

ISSN:0002-9505    

DOI:10.1119/1.1975392

出版商:American Association of Physics Teachers    

年代:1969

数据来源: AIP

摘要:

The concept of the force exerted by a quantum-mechanical particle is examined. Two expressions for this force, one local and one nonlocal, are derived, and shown to be equivalent. These results are applied to a discussion of the transmission of force by a single electron and to an elementary derivation of the Fermi-Segrè formula.

ISSN:0002-9505    

DOI:10.1119/1.1975394

出版商:American Association of Physics Teachers    

年代:1969

数据来源: AIP

摘要:

We give a method to obtain the energy bands for a “one-dimensional doubly periodic potential”; some numerical results are presented.

ISSN:0002-9505    

DOI:10.1119/1.1975396

出版商:American Association of Physics Teachers    

年代:1969

数据来源: AIP

摘要:

An experiment is described to determine the average velocity of gas molecules in a container while effusion takes place through a small hole into vacuum. When the mean free path of the molecules becomes large compared to the hole diameter, the measurement of pressure as a function of time permits the average velocity to be extracted. The equipment and procedure are simple, and an agreement to within 10% of the kinetic theory of gas value has been obtained using an inexpensive McLeod gauge. The experiment has been performed using air, helium, and argon; measurements on air and helium were performed both at room and dry ice temperatures. A formula has been derived to take into account the effect of outgassing of the container walls at low pressures. Average velocities may be extracted either by a hand calculation between pairs of data points, or by using a short computer program for least-squares analysis. A derivation is given in an Appendix for the effect on the effusion of the hole being drilled in a wall of thickness small, but not negligible, compared to the hole diameter. During the initial pump-down period, while the container pressure is still comparable to atmospheric, the pressure-versus-time data can be analyzed in terms of hydrodynamic theory and used to deduce a virtual hole area for the streaming molecules. Measurements of pressure-increase with time in a sealed-off system gave poor agreement with the rate of outgassing needed to fit the effusion data.

ISSN:0002-9505    

DOI:10.1119/1.1975398

出版商:American Association of Physics Teachers    

年代:1969

数据来源: AIP

摘要:

The continuity equations are solved in the Faraday dark space for an idealized geometry. By invoking the superposition principle, the electric field may be divided into two components: one of which is responsible for maintaining charge neutrality, and the second of which is responsible for current flow. By conceptually dividing the electric field in this way, it is possible to visualize easily the transitions in the current-carrying mechanisms in the Faraday dark space as the anode-cathode separation is increased. The criteria for the appearance of a positive column is also clearly illustrated.

ISSN:0002-9505    

DOI:10.1119/1.1975402

出版商:American Association of Physics Teachers    

年代:1969

数据来源: AIP

摘要:

A simple nonlinear partial differential equation suitable for study by an undergraduate in applied science is discussed. Several physical realizations are outlined and the construction of an analog model is described. The equation is analyzed to determine nonlinear pulse and periodic waveforms, and the stability of these waveforms is investigated using a recently developed “averaged Lagrangian” technique.

ISSN:0002-9505    

DOI:10.1119/1.1975404

出版商:American Association of Physics Teachers    

年代:1969

数据来源: AIP

摘要:

This paper reports an experiment for an advanced laboratory. The experiment concerns superconductive tunneling measurements of the variation of the energy gap in lead with temperature. The tunneling occurs between evaporated aluminum and evaporated lead films which are separated by an aluminum oxide insulator. The experiment is performed by dipping the samples into a liquid-helium storage Dewar and uses very little helium. The measurements include the variation of the energy gap in lead between 4.2°K and the transition temperature of the lead film. Student data are used in the figures.

ISSN:0002-9505    

DOI:10.1119/1.1975406

出版商:American Association of Physics Teachers    

年代:1969

数据来源: AIP