摘要:

An experiment is described in which students in an introductory laboratory can determine all of the relevant energy flows (and hence the coefficient of performance) of an ordinary household refrigerator and can compare their measured results with the coefficient for an ideal Carnot refrigerator operating between the same two temperatures. The analysis of the data makes use of the first and second laws of thermodynamics and the relationship for thermal conductivity. The experiment has relevance in the world of the energy crisis.

ISSN:0002-9505    

DOI:10.1119/1.10361

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

摘要:

We review some general properties of density and scattering matrices and composite spin spaces of spin‐1/2 particles. We give a derivation of a useful expansion of spin expectation values. The expansion is used in a number of simple examples. Spin tensors and pure spin cross sections are introduced.

ISSN:0002-9505    

DOI:10.1119/1.10362

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

摘要:

It is well known that, when a weight hanging on a spring oscillates up and down, the spring, owing to its mass, has some effect on the motion and, in particular, on the period. Both exact and approximate solutions to that problem have been given. Likewise, the cord of a simple pendulum, because of its mass, has some effect on the motion and on the period. The solution to the problem is investigated here. It leads to a rather complicated equation involving Bessel functions of both kinds. However, it is possible to find simpler approximations which are likely to be legitimate in practice. Also, the results obtained are compared with some other arrangements, which seem physically to have some resemblance to the cord and pendulum bob, and which can be solved fairly readily.

ISSN:0002-9505    

DOI:10.1119/1.10378

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

摘要:

Conditions on wave functions that are eigenvectors often have a mathematical rather than a physical basis; they are required simply because an eigenvector of an operator must be in the domain of that operator. This is illustrated with derivations of the conditions at the origin on eigenvectors of a nonrelativistic Hamiltonian, for example, for the hydrogen atom or harmonic oscillator, and the condition that eigenfunctions of the angular momentumLzmust be single valued or continuous around a complete circle.

ISSN:0002-9505    

DOI:10.1119/1.10379

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

摘要:

The exactly soluble model, originally considered by Moshinsky, consisting of two spin‐1/2 particles interacting through harmonic‐oscillator forces and moving in a common harmonic‐oscillator potential is extended to include the effects of an external electric field. We solve for the energy exactly, exactly in the Hartree–Fock approximation, and also compare to the results of Hartree–Fock perturbation theory. We find that the Hartree–Fock method yields the same result for the electric polarizability as the exact solution even though the field‐independent part of the energy is not the same. However, when second‐order Hartree–Fock perturbation theory is employed, the results for the polarizability can be substantially in error. Similar results obtain for the calculation of the matrix element for optical absorption in the dipole approximation.

ISSN:0002-9505    

DOI:10.1119/1.10380

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

摘要:

The transcendental equations that determine the bound‐state energy eigenvalues of the one‐dimensional square well and thesstates of the three‐dimensional well are cast into a form that can easily be solved to high accuracy on a pocket calculator. Numerical examples of various one‐dimensional wells and the deuteron are presented.

ISSN:0002-9505    

DOI:10.1119/1.10381

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

摘要:

In the analysis of electronic circuits, it is often useful to replace a network by its Thevenin equivalent circuit. To do this one needs to calculate the values of the equivalent voltage and series resistance. It is shown that the prescription for finding the equivalent resistance given by most electronic texts is not generally valid when the network contains sources whose strength is controlled by currents within the network. In fact, the source strength coefficients appear in the expression for the equivalent resistance, yet would be eliminated by the usual method of short‐circuiting the sources. A correct method of derivation is given and the emitter–follower circuit is shown as an example.

ISSN:0002-9505    

DOI:10.1119/1.10382

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

摘要:

The rotating charged sphere is discussed as a model for particle spin. The nonrelativistic classical mechanics of the model shows a close analogy to the nonrelativistic (Pauli) quantum mechanics of spin. The spin contribution to the Hamiltonian operator, −γŝ⋅B (standard notation), represents the nonconstant part of the kinetic energy associated with spin. Variations of translational kinetic energy in an inhomogeneous static magnetic field are offset by variations of spin kinetic energy. The latter, along with the torque term responsible for them, cannot be overlooked without forfeiting conservation of energy.

ISSN:0002-9505    

DOI:10.1119/1.10383

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.10384

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.10363

出版商:American Association of Physics Teachers    

年代:1976

数据来源: AIP