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| − | Sodium Vapour Lamp consists of a discharge tube created from a heat resistant glass, containing a small amount of metallic sodium, neon gas and two electrodes, Neon gas is added to start off the discharge and to develop adequate heat to vaporize the sodium. Due to the fact of law pressure inside the tube, a sufficiently extended tube essential to obtain more light. To minimize the overall dimension of the lamp, this tube is usually bent into U-shape.<br><br>The light created by this lamp is yellowish which is created at its optimum pressure of about .004mm of mercury. This pressure is obtained at a temperature of about 280 C and so it becomes necessary to sustain this temperature. For this purpose the U-tube is enclosed in a double walled flask to avoid shed of heat. The double walled flask is interchangeable and can be fitted on to an additional U-tube. Whilst replacing the inner U-tube 1 need to be extremely careful due to the fact if it is broken [http://www.youtube.com/watch?v=qJHVMcI4cks&feature=plcp chicken houses] and sodium comes in get in touch with with moisture, it may possibly result in fire.<br><br>All electric discharge lamps demand a greater voltage at the time of beginning and low voltage for the duration of operation. Usually, sodium vapour lamps are operated by a high leakage reactance transformer. At starting a high voltage of about 450 volts is applied across the lamp which is sufficient to begin the discharge. When the lamp is completely operative immediately after 10 - 15 minutes, the voltage across it falls to about 150 volts. Simply because of the high reactance of circuit, the power aspect is low and hence a p.f improvement capacitor is connected.<br><br>The efficiency of a low pressure sodium vapour lamp is really high (about 40 - 50 lumens/watt) and it produces a light of distinct wavelength having yellow color. Sodium lamps are primarily employed for street, high way and airfield lighting where color distinction is not so required.
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Текущая версия на 11:44, 26 декабря 2025
