摘要:

The classical electromagnetic fields are usually described by six independent functions of space and time, namely the three components of the electric field and the three components of the magnetic field, satisfying Maxwell's equations. On the other hand it is well known that all observable effects of these fields can be derived from five components of the electromagnetic stress-energy tensor. Consequently the usual description contains one superabundance, that can be described by one parameter φ which cannot be measured experimentally but must be fixed by an arbitrary convention. Implicit conventions concerning φ, underlying the usual approach to electromagnetic fields tend to obscure the understanding and should be replaced by an explicitly stated convention. It is recommended that this convention be that φ be defined zero for electrons.

ISSN:0002-9505    

DOI:10.1119/1.1971484

出版商:American Association of Physics Teachers    

年代:1965

数据来源: AIP

摘要:

Many Van de Graaff accelerator-type experiments can be performed at modest and even low bombarding energies. In general, for incident particle energies below 150 keV, one is restricted to proton- or deuteron-induced reactions on light target nuclei. This restriction is, of course, due to the Coulomb barrier for most reactions in this energy interval. Several reactions which are feasible with existing equipment found in many universities throughout the United States and foreign countries are discussed. Necessary modifications to existing Cockcroft-Walton-type accelerators are outlined, and the general experimental procedures for reactions of the type12C(p,p) 12Cand11B(p,α) 8Beare given.

ISSN:0002-9505    

DOI:10.1119/1.1971487

出版商:American Association of Physics Teachers    

年代:1965

数据来源: AIP

摘要:

For a simple class of Hamiltonians of a continuous medium it is shown that the condition of translational invariance implies a zero-energy gap in the excitation spectrum. It is also shown that because of translational symmetry a spurious state of zero energy and momentum exists for an electron plasma in a positive background. This spurious state becomes massive when translational symmetry is broken.

ISSN:0002-9505    

DOI:10.1119/1.1971489

出版商:American Association of Physics Teachers    

年代:1965

数据来源: AIP

摘要:

Two air-supported devices are described. One is an air-bearing gyroscope and the other a classical “nuclear” magnetic resonance apparatus using an air-bearing gyroscope.

ISSN:0002-9505    

DOI:10.1119/1.1971491

出版商:American Association of Physics Teachers    

年代:1965

数据来源: AIP

摘要:

The design and development of an apparatus for measuringe/mof β particles as a function of velocity is described. A 10 mCi source, such as90Sror137Cs, is used to provide a range of high-speed electrons. A magnetic field-momentum selector and a crossed magnetic and electric field-velocity selector provide the elements of the experimental apparatus. The same magnetic field is used in both selectors and this field is provided by an inside-out electromagnet, which may be described as an iron pillbox with the energizing coil on the inside. The iron pillbox also serves as the vacuum chamber. The electrons are detected by a GM or solid-state counter. Provisions for measuring the magnetic and electric fields are described. The results obtained by use of the apparatus are given. Such results can be duplicated by students in one or two laboratory sessions of the normal three-hour length. A continuing program of development of experiments with the apparatus is described.

ISSN:0002-9505    

DOI:10.1119/1.1971493

出版商:American Association of Physics Teachers    

年代:1965

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.1971496

出版商:American Association of Physics Teachers    

年代:1965

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.1971497

出版商:American Association of Physics Teachers    

年代:1965

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.1971499

出版商:American Association of Physics Teachers    

年代:1965

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.1971500

出版商:American Association of Physics Teachers    

年代:1965

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.1971501

出版商:American Association of Physics Teachers    

年代:1965

数据来源: AIP