Experiments and Demonstrations in Physics - Bar-Ilan Physics Laboratory

2008

Eur. J. Phys.

Self Cite

An experiment and a demonstration concerning transport by magnetic levitation (Maglev) are described. The lift, drag and radial forces on a magnet placed over a rotating conducting disc are measured versus the rotation frequency. The experiment relates to important topics of electromagnetism and could be a useful addition to the undergraduate physics laboratory. The clearly seen electrodynamic suspension is an attractive classroom demonstration.

Section: Methodsmentioning

confidence: 99%

Maglev for students

2008

Eur. J. Phys.

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“…A significant disadvantage of fluorescent lamps is the use of mercury, a harmful source of environmental pollution. For student experiments with fluorescent lamps, see [7][8][9] and references therein.…”

Section: Fluorescent Lightingmentioning

confidence: 99%

Nobel Prize for blue LEDs

2015

Eur. J. Phys.

A brief review of lighting technologies is presented. Unavoidable restrictions for incandescent light bulbs caused by the Planck distribution and properties of the human eye are illustrated. The efficiency and luminous efficacy of thermal radiation are calculated for various temperatures; the results clearly show the limitations for thermal radiators. The only way to overcome these limitations is using non-thermal radiators, such as fluorescent lamps and light-emitting diodes (LEDs). Unique advantages of LEDs undoubtedly made a revolution in this field. A crucial element of this progress is the blue LEDs (Nobel Prize 2014). Some experiments with a blue and a green LED are described: (i) the luminescence triggered in a green-yellow phosphor inside a white LED by the blue LED; (ii) radiant spectra and 'efficiency droop' in the LEDs; (iii) modulation of the blue LED up to 4 MHz; and (iv) the h/e ratio from the turn-on voltage of the green LED. The experiments are suitable for undergraduate laboratories and usable as classroom demonstrations.

“…An experiment focused on the principles of radio communication was described earlier. 1,2 It turns out that a demonstration of key principles of television transmission and reception is possible with a relatively simple experimental setup if one focuses only on black-and-white television signals. The McGraw-Hill Encyclopedia 3 serves as a handbook on the many radio and television techniques discussed here.…”

Section: Introductionmentioning

confidence: 99%

Video through a light guide

American Journal of Physics

2008

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Demonstrations are discussed to illustrate some basic principles of television transmission and reception. The aim of these demonstrations is to promote student understanding of how a picture is converted into an electrical signal, sent to a remote receiver, and correctly reproduced there. The demonstration setup includes a video camera, a light emitting diode, a light guide, a photodiode, and a video monitor. Electrical production of visual images is also discussed.