Luminous and Magnetic Flux
From High School Online Collaborative Writing
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[edit] History
Luminous Flux by definition, is the measure of the percieved power of light. The purpose of Luminous Flux is to measure and represent the level of sensitivity of the human eye. Magnetic Flux by definition, is the quantitative measurment of magnetism, taking in consideration the strength and power of a magnetic field. Both of these types of measurments were created and used in basic SI Photometry tables. The national SI standards of luminous intensity, illuminance and luminous flux are realized and extended to luminance and transmittance. SI units are maintained and disseminated with the status of national reference laboratory. The Department participates in the activity of the Consultative Committee for Photometry and Radiometry (CCPR) and the Commission Internationale de l’Eclairage (CIE). Dissemination is provided by calibration activity, through the Italian Calibration Service (SIT). Measurement services to users include calibrations of detectors and light sources, photometric characterization of lighting and signaling systems, characterization of reference materials and materials for lighting applications.
[edit] Luminous Flux
Luminous Flux - lumen (=cd.sr)
Luminous Flux is simply the measure of energy and power emmited from any light source. The best example of a material that measures varying Lumninous amounts, is a light bulb. Certain light bulbs emmit different levels and amounts of Luminous Flux (Lumens). Do not confuse the purpose of Luminous Flux as being the brightness of a light emmiting from a source. It is rather the measure of "useful" power emmited by a light source which in turn, is the sum of all wavelengths emmited by the varying levels of Luminous Flux.
[edit] Luminous Flux Example Problem
Illumination Of A Surface
What is the illumination on your desktop if it is lighted by a 1750-lm lamp that is 2.50m above your desk?
Sketch The Problem
1.) Assume that the bulb is the point source.
2.) Diagram the position of the bulb and desktop. Label P and D.
Calculate Your Answer
Known:
Luminous Flux, P=1750lm
d=2.50m
Strategy:
The surface is perpendicular to the direction the light ray is traveling, so you can use the illuninance equation.
Unknown:
Illuminance, E=?
[edit] Magnetic Flux
Magnetic Flux - BA
Measurement of the strength of the magnetic field around electric currents and magnets. Its SI unit is the weber; one weber per square metre is equal to one tesla. The amount of magnetic flux through an area equals the product of the area and the magnetic field strength at a point within that area.
[edit] Magnetic Flux Example Problem
1.)
The metal rod in the figure is sliding along a U-shaped track as shown. There is a magnetic field in the blue region which is into the figure. What is the direction of the current in the sliding rod?
2.)In the above question, if B = 0.4 T, L = 0.5 m, and v = 3 m/s, what is the magnitude of the induced EMF?
a. 3volts
b. 2.6volts
c. 0.6 volts
d. 0 volts
[edit] Resources
http://hyperphysics.phy-astr.gsu.edu/Hbase/magnetic/fluxmg.html Diagram For Magnetic Flux
http://en.wikipedia.org/wiki/Luminous_Flux Luminous Flux Reference
http://en.wikipedia.org/wiki/Photometry_%28optics%29 Photometry Reference
http://en.wikipedia.org/wiki/Luminous_energy Luminous Flux SI Table Reference
http://en.wikipedia.org/wiki/Magnetic_Flux Magnetic Flux Reference
http://chem.ch.huji.ac.il/~eugeniik/history/weber.html History Of Luminous And Magnetic Flux Reference
