ISSN:0002-9505    

DOI:10.1119/1.18653

出版商:American Association of Physics Teachers    

年代:1997

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.18745

出版商:American Association of Physics Teachers    

年代:1997

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.18654

出版商:American Association of Physics Teachers    

年代:1997

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.18783

出版商:American Association of Physics Teachers    

年代:1997

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.18667

出版商:American Association of Physics Teachers    

年代:1997

数据来源: AIP

摘要:

In ways no one predicted physics in our time has been astonishingly useful and continually surprising. Has our teaching kept up? Some thoughts about tools and ideas from physics for the college student who wants to be some kind of scientist. [Reprinted fromAAPT Pathways(Proceedings of the Fiftieth Anniversary Symposium of the AAPT), edited by Melba Phillips (American Association of Physics Teachers, Stony Brook, New York, 1981)]

ISSN:0002-9505    

DOI:10.1119/1.18635

出版商:American Association of Physics Teachers    

年代:1997

数据来源: AIP

摘要:

All known elementary particles that can be isolated asindividualparticles have an electric charge that is equal in magnitude to the electron’s charge,q=1.6×10−19 C,or is zero. This includes the muon and tau charged leptons, the neutrinos, the photon, the nucleons, and the mesons. There have been many searches without confirmed success for isolated particles with fractional electric charge such as±q/3,or±q/2,or±3q/2.The theory of the physics of elementary particles does not require the existence of such particles. In particular, current theory holds that quarks, whose charge is±(1/3)qor±2/3q,cannot be isolated. Despite past failures and current theory, we have been engaged for the past few years in a new search for isolated elementary particles with fractional electric charge. In the course of this paper we discuss models for fractional charge particles, summarize previous searches, and describe our experimental method; and because this is speculative research we will also present our thoughts on speculative experiments.

ISSN:0002-9505    

DOI:10.1119/1.18641

出版商:American Association of Physics Teachers    

年代:1997

数据来源: AIP

摘要:

Rutherford envisioned the proton in 1914 when experiments on alpha-particle scattering led him to suggest that the hydrogen nucleus was the carrier of both positive charge and mass in the structure of all heavier atoms. This was supported by his discovery in 1919 that bombardment by alpha particles expelled hydrogen from nitrogen. In 1920, he proposed the nameprotonfor the hydrogen nucleus in this role but refrained from using it, perhaps from what he considered a lack of direct experimental evidence. That constraint continued as he and Chadwick found hydrogen expelled from most other light nuclei. He abandoned it at last when Blackett’s cloud chamber showed the capture of the alpha particle by a nitrogen nucleus at the time the proton was emitted.

ISSN:0002-9505    

DOI:10.1119/1.18640

出版商:American Association of Physics Teachers    

年代:1997

数据来源: AIP

摘要:

A novel design for simulating a lumped element transmission line is described. Op-amp subcircuits replace discrete inductances—an approach which overcomes a number of disadvantages associated with conventional components. The apparatus models a lossy line which is free of amplitude and phase distortion. Experiments are described which demonstrate the design’s precise measurement capabilities with respect to determining frequency-dependent input impedance and phase shift, as well as the real and imaginary parts of the complex propagation function. Several pulse experiments are also discussed.

ISSN:0002-9505    

DOI:10.1119/1.18782

出版商:American Association of Physics Teachers    

年代:1997

数据来源: AIP

摘要:

An investigation of students’ knowledge after a traditional advanced high-school course in electromagnetism shows deficiencies of their knowledge in three major areas: (1) the structure of knowledge—e.g., realizing the importance of central ideas, such as Maxwell’s equations (expressed qualitatively); (2) conceptual understanding—e.g., understanding the relationships between the electric field and its sources; and (3) application of central relationships in problem solving. To remedy these deficiencies we propose an instructional model which integrates problem solving, conceptual understanding and the construction of the knowledge structure. The central activity of the students is a gradual construction of a hierarchical concept map organized around Maxwell’s equations as central ideas of the domain. The students construct the map in five stages: (1) SOLVE—they solve a set of problems that highlight the central ideas in the domain; (2) REFLECT—they reflect on the conceptual basis of their solutions; (3) CONCEPTUALIZE—they perform activities that deal with relevant conceptual difficulties; (4) APPLY—they carry out complex applications; (5) LINK—they link their activities to the evolving concept map. This integrative model (experimental treatment) was compared to an isolated treatment of drill and practice or treatment of conceptual difficulties without linkage to the proposed knowledge structure. The comparison shows that students in the experimental treatment performed better than the other students on measures of recall, conceptual knowledge and problem solving. Students in the experimental treatment were also able to transfer and extract central ideas in a domain different than physics.

ISSN:0002-9505    

DOI:10.1119/1.18642

出版商:American Association of Physics Teachers    

年代:1997

数据来源: AIP