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Sodium Vapour Lamp consists of a discharge tube made from a heat resistant glass, containing a modest amount of metallic sodium, neon gas and two electrodes, Neon gas is added to commence the discharge and to develop enough heat to vaporize the sodium. Since of law pressure inside the tube, a sufficiently extended tube necessary to obtain much more light. To lessen the all round dimension of the lamp, this tube is generally bent into U-shape.

The light developed by this lamp is yellowish which is produced at its optimum pressure of about .004mm of mercury. This pressure is obtained at a temperature of about 280 C and so it becomes essential to preserve this temperature. For this goal the U-tube is enclosed in a double walled flask to prevent shed of heat. The double walled flask is interchangeable and can be fitted on to one more U-tube. Although replacing the inner U-tube one need to be very cautious because if it is broken and sodium comes in contact with moisture, it may result in fire.

All electric discharge lamps call for a greater voltage at the time of beginning and low voltage in the course of operation. Generally, 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 adequate to begin the discharge. When the lamp is completely operative right after ten - 15 minutes, the voltage across it falls to about 150 volts. Due to the fact of the high reactance of circuit, the power element is low and hence a p.f improvement capacitor is connected.

The effectiveness of a low pressure sodium vapour lamp is extremely high (about 40 - 50 lumens/watt) and it produces a light of certain wavelength obtaining yellow color. Sodium lamps are primarily employed for street, high way and airfield lighting where color distinction is not so required. electronic cigarette v2 cigs coupon v2 cigs coupon code