ISSN:0002-9505    

DOI:10.1119/1.18000

出版商:American Association of Physics Teachers    

年代:1995

数据来源: AIP

摘要:

Improvements to the Millikan oil drop experiment as it is performed in teaching laboratories are described. Enhancement of the optics in the oil‐drop apparatus greatly improves the visibility of the drops. Accurate timing of their motion becomes possible since they are now bright and sharply focused. With improved timing, the parameters such as microscope calibration and plate separation can become the principal sources of experimental error. Methods are described to accurately determine these experimental parameters. The workload for the experimenter is greatly reduced by using a computer to: act as a smart stopwatch, calculate the drop charge in real time, perform the statistics, and make records of the experiment. The convenience and speed offered by the computer, coupled with improved optics, relieves the eyestrain, fatigue, and frustration usually associated with this experiment. Nye’s watch oil was used in this study. A return to Millikan’s original iteration method for the correction to Stokes’ law lowers the calculated charge for small drops by about 2%. With these improvements the calculated charges are sufficiently accurate that guesswork as to the multiplicity of their charge is essentially eliminated. A student typically obtains the value of the electronic charge accurate to about 1% with 1 h of experimentation. Student and instructor satisfaction are much improved.

ISSN:0002-9505    

DOI:10.1119/1.18001

出版商:American Association of Physics Teachers    

年代:1995

数据来源: AIP

摘要:

We briefly describe a new view of the science learner that has emerged from recent research and then discuss how we have built on this view to design a physics course for prospective elementary teachers. The main goals are to help students develop robust conceptual models in various physics domains and to help them become more aware of, and more responsible for, their own learning. The integrated set of course activities to help promote these goals includes the use of highly interactive multimedia computer programs and the writing and collaborative peer evaluations of comprehensive explanations of novel phenomena. Evidence is provided to suggest that the total course environment has helped accomplish our goals.

ISSN:0002-9505    

DOI:10.1119/1.18085

出版商:American Association of Physics Teachers    

年代:1995

数据来源: AIP

摘要:

We formulate the problem of a gravitationally collapsing body in terms of a single set of coordinates that are employed both in the vacuum region outside the body and inside the body where there is a zero pressure perfect fluid. The spatial coordinateRis the usual Schwarzschild radial coordinate, while the time coordinatetis measured by radially falling geodesic clocks. It is possible to follow the collapse of the body entirely on a single (R,t) space–time diagram. We give analytical expressions for the metrics in the interior and exterior regions which join smoothly and naturally at the surface of the collapsing body. Other features such as apparent and event horizons are also described.

ISSN:0002-9505    

DOI:10.1119/1.18002

出版商:American Association of Physics Teachers    

年代:1995

数据来源: AIP

摘要:

The computer‐assisted personalized assignment system has been used to prepare and present conceptual, qualitative questions to students in large introductory classes. The questions appear to be effective in helping students to grasp concepts, as they stimulate dialogue and discussion among the students while they are seeking correct solutions, and provide the instructor with feedback on difficulties students encounter with certain concepts. No formal evaluation of the effectiveness of these questions has been made. Many conceptual, qualitative questions for introductory physics have been written with this system and used in assignments. Several examples are given and briefly discussed.

ISSN:0002-9505    

DOI:10.1119/1.18044

出版商:American Association of Physics Teachers    

年代:1995

数据来源: AIP

摘要:

By means of supersymmetric quantum mechanics, we provide a new simple proof that discrete eigenstates, i.e., bound states, of any one‐dimensional quantum system satisfying the time‐independent Schrödinger equation without internal degrees of freedom are nondegenerate. Using the same idea, we show that the ground state of anN‐dimensional time‐independent Schrödinger equation without internal degrees of freedom is nondegenerate, too. Reasons why degeneracy is possible for excited states whenN≳1 are also discussed.

ISSN:0002-9505    

DOI:10.1119/1.18045

出版商:American Association of Physics Teachers    

年代:1995

数据来源: AIP

摘要:

A teaching‐style inventory based on the American Association of Physics Teachers workshop,DevelopingStudentConfidenceinPhysicswas administered to Danish and American teachers. There are some national differences in responses; however, they do not appear to account for the much higher levels of confidence measured in Danish students. Explanations are proposed for the cause of these differences, as well as for the gender bifurcation among both Danish and American students. In addition, the Danish teachers in this study undertook a critique of the AAPT inventory, and proposed additional and alternate scenarios for assessment of relationship and content in the physics classroom.

ISSN:0002-9505    

DOI:10.1119/1.18046

出版商:American Association of Physics Teachers    

年代:1995

数据来源: AIP

摘要:

We calculate the moments of inertia ofD‐dimensional spheres and spherical shells, whereDis a complex number. We also examine the moments of inertia of fractional‐dimensional geometrical objects such as the Cantor set and the Sierpinski carpet and theirD‐dimensional analogs.

ISSN:0002-9505    

DOI:10.1119/1.18097

出版商:American Association of Physics Teachers    

年代:1995

数据来源: AIP

摘要:

The use of a set of partial ring pendula of equal radii as the basis for an interesting laboratory experiment is discussed. Sources of systematic errors are analyzed and theoretical calculations are presented for nonidealized partial rings. These calculations are found to be in good agreement with experimental results within measured uncertainties.

ISSN:0002-9505    

DOI:10.1119/1.18047

出版商:American Association of Physics Teachers    

年代:1995

数据来源: AIP

摘要:

In the framework of quantum theory, we present one theorem and three corollaries regarding the direct connection between constants of motion of a physical system and degeneracies of its energy eigenvalues. It is shown that this connection emerges when there exist quantum operators which commute with the Hamiltonian, but not with each other. Further it is shown that if the commutator of these operators is a nonvanishing constant number then (a) all the eigenvalues of the system are degenerate, and (b) the degree of degeneracy is infinite. A number of examples are discussed including the parity degeneracy of the hydrogen atom and the infinite degeneracy of the Landau levels of a charged particle in a constant magnetic field.

ISSN:0002-9505    

DOI:10.1119/1.18048

出版商:American Association of Physics Teachers    

年代:1995

数据来源: AIP