摘要:

A general description of the phenomena of ferroelectricity is given together with a brief history of the subject. A comparison is made between ferroelectricity and ferromagnetism.Next, a more detailed description is made of the properties of the three main types of ferroelectrics: the barium titanate, KDP (potassium dihydrogen phosphate), and Rochelle salttypes. Finally the electrical properties of these substances are discussed in relation to their crystal structures.

ISSN:0002-9505    

DOI:10.1119/1.1933948

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

This is a report of sessions in which engineers and physicists met to consider possible re visions of physics instruction in engineering education. The Interim Report of the ASEE Committee on Evaluation of Engineering Education and the responses of physics departments to a questionnaire prepared by committees of ASEE and AAPT provided the chief bases for the discussion.

ISSN:0002-9505    

DOI:10.1119/1.1933950

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

Large convection currents in some laboratory liquids are made easily visible by a fine suspension of aluminum flakes. Ample contrast is available for photography. Acetone is the most practical of those liquids tested. A heat source such as a finger and a heat sink due to evaporation of the liquid are sufficient to set a small beakerful into motion at speeds around one cm/sec. A two-dimensional flow table was constructed without pumps or plumbing. Such flow is continous and long-lasting. Only a small occasional replenishment of liquid, to make up for that lost by evaporation, is necessary.

ISSN:0002-9505    

DOI:10.1119/1.1933951

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

Attention is drawn to the application of Ohm's law to a portion of a direct-current series circuit containing both sources of emf and resistance elements. Circuits are presented wherein for a portion of the series circuit the difference in potential,V, and the current,I, satisfy separately the three following situations:—(1)V ≠ 0andI = 0, (2)V = 0andI = 0, (3)V = 0andI ≠ 0.

ISSN:0002-9505    

DOI:10.1119/1.1933952

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

An account is given of recent results obtained from the study of the infrared solar spectrum with modern grating spectrometers and detectors. The discussion is divided into three parts, namely, the sun's continuous spectrum, the solar absorption-line spectrum, and the telluric- or terrestrial-line spectrum.

ISSN:0002-9505    

DOI:10.1119/1.1933953

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

If we may except the spectacle lens, the earliest device worthy to be called an optical instrument was thecamera obscura. A remarkably fine diagram of this instrument, given by Leonardo da Vinci, is reproduced here. It is probably the earliest delineation of an optical instrument that we have.

ISSN:0002-9505    

DOI:10.1119/1.1933954

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

摘要:

In 1659 Christiaan Huygens invented the pendulum clock and realizing the lack of isochronism in a simple pendulum, he mounted it between cycloidal cheeks. After many years of trying to adapt this clock to seagoing vessels to determine longitude, he suggested, in 1675, the use of a balance wheel with an elastic wire to control oscillation. At this time the “theory of elasticity” was not sufficiently developed to analyze his balance arrangement.The first successful effort to establish the laws of isochronism for a balance governed by spiral springs was made by Phillips (Annales des Mines, Tome XX, 1861). However, he did not discuss the problems raised by the use of regulator pins.The present paper deals with the isochronal balance as influenced by the functioning of spiral springs equipped with regulator pins. To insure isochronal motion of a balance, the inner end of spiral regulator must act on the balance with a pure torque (a moment unaccompanied by any linear reactions), and this torque must be linearly proportional to the angular displacement of the balance. The design of terminals with regulator pins resolves itself to the problem of finding its shape so as to insure isochronal motion.

ISSN:0002-9505    

DOI:10.1119/1.1933955

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.1933956

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.1933958

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP

ISSN:0002-9505    

DOI:10.1119/1.1933959

出版商:American Association of Physics Teachers    

年代:1955

数据来源: AIP