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# Stefan's constant

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here u can got thepics of determination of Stefan's constant by using LDR and incandescent bulb

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• Where do you get this formula: Stefan's cont = 2.43 X 10 (-4) { Vs’/ T}
Can you please mention where can i get the derivation?

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### Stefan's constant

1. 1. Determine the Stefan's constant using incandescent lamp and photo voltaic cell.<br />Trisha Banerjee @ 2010<br />
2. 2. Incandescent lamp<br />Photovoltaic cell<br />Power supply<br />Trisha Banerjee @ 2010<br />
3. 3. Object:- To determine the Stefan's constant by using an incandescent lamp and the photovoltaic cell.<br />Apparatus:- <br /> 1) A regulated supply 0- 15 V and 0- 5 amp.<br /> 2) An incandescent lamp 6 V , 12 W with lamp house .<br /> 3) A photovoltaic cell mounted in a house.<br /> 4) optical bench with two strands , one for lamp to use the other for photovoltaic cell.<br /> 5) A unit is operative on 230 V = 10% at 50 Hz AC mains.<br />Trisha Banerjee @ 2010<br />
4. 4. Both are hidden by a dark cover.<br />Trisha Banerjee @ 2010<br />
5. 5. Power supply:-<br />Vg<br />Ig<br />Trisha Banerjee @ 2010<br />
6. 6. Incandescent light:-<br />Trisha Banerjee @ 2010<br />
7. 7. incandescent lamp :-<br />The incandescent light bulb, incandescent lamp or incandescent light globe is a source of <br />electric light that works by incandescence (a general term for heat-driven light emissions, <br />which includes the simple case of black body radiation). An electric current passes through a thin filament, heating it to a temperature that produces light. The enclosing glass bulb <br />contains either a vacuum or an inert gas to prevent oxidation of the hot filament. Incandescent bulbs are also sometimes called electric lamps, a term also applied to the original arc lamps.<br />Incandescent bulbs are made in a wide range of sizes and voltages, from 1.5 volts to about 300 volts. They require no external regulating equipment and have a low manufacturing cost, and work well on either alternating current or direct current. As a result the incandescent lamp is widely used in household and commercial lighting, for portable lighting such as table lamps, car headlamps, and flashlights, and for decorative and advertising lighting.<br />Trisha Banerjee @ 2010<br />
8. 8. Photo voltaic cell:-<br />Photovoltaic's is the direct conversion of light into electricity at the atomic level. Some<br />materials exhibit a property known as the photoelectric effect that causes them to absorb photons of light and release electrons. When these free electrons are captured, an electric current results that can be used as electricity.<br />The photoelectric effect was first noted by a French physicist, Edmund Bequerel, in 1839, who found that certain materials would produce small amounts of electric current when exposed to light. In 1905, Albert Einstein described the nature of light and the photoelectric effect on which photovoltaic technology is based, for which he later won a Nobel prize in physics. The first photovoltaic module was built by Bell Laboratories in 1954. It was billed as a solar battery and was mostly just a curiosity as it was too expensive to gain widespread use. In the 1960s, the space industry began to make the first serious use of the technology to provide power aboard spacecraft. Through the space programs, the technology advanced, its reliability was established, and the cost began to decline. During the energy crisis in the 1970s, photovoltaic technology gained recognition as a source of power for non-space applications.<br />Trisha Banerjee @ 2010<br />
9. 9. The diagram above illustrates the operation of a basic photovoltaic cell, also called a solar cell. Solar cells are made of the same kinds of semiconductor materials, such as silicon, used in the microelectronics industry. For solar cells, a thin semiconductor wafer is specially treated to form an electric field, positive on one side and negative on the other. When light energy strikes the solar cell, electrons are knocked loose from the atoms in the semiconductor material. If electrical conductors are attached to the positive and negative sides, forming an electrical circuit, the electrons can be captured in the form of an electric current -- that is, electricity. This electricity can then be used to power a load, such as a light or a tool.<br />Trisha Banerjee @ 2010<br />
10. 10. Principle in brief:- <br /> here we are using the relation <br /> Stefan's cont = 2.43 X 10 (-4) { Vs’/ T} <br /> result in joule per sqr meter per sec per quad Kelvin.<br />Where Vs’ = Vo +Vs in volts with Vo volts corresponding to work function of photo cathode and Vs volt corresponding to maximum kinetic energy of photo electrons which in turn correspond to photon’s of maximum energy emitted by a black body at temperature T Kelvin ( temperature of the incandescent filament which acts as a black body radiator.<br /> Vo= minimum work function , i.e. obtain from the intercept on the Y – axis obtain from the graph of Vs( mV) and T ( in Kelvin)<br />Vs = voltage of the photovoltaic cell obtain from multimeter.<br />Here Ro should be calculated properly i.e. (Rg X 3.9 ) ohm , and Rg= Vg/Ig . <br />And Ig and Vg are obtained carefully which is obtained by just illumination or glow of the lamp in dark.<br />Initially we have to measure Rg . So for this power supply should be at minimum , i.e. fully anticlock.<br />Trisha Banerjee @ 2010<br />
11. 11. Precaution:- <br /> 1) carefully find out the glow resistance Rg of filament by taking Vg voltage drop across the filament when Ig is ampere current passes through it and just makes it to glow.<br /> 2) carefully take the readings of Vs through multimeter of photovoltaic cell.<br />Trisha Banerjee @ 2010<br />