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The Mercury Vapor Lamp

المؤلف:  GEORGE A. HOADLEY

المصدر:  ESSENTIALS OF PHYSICS

الجزء والصفحة:  p-422

2025-12-24

630

When a tube, having a terminal at each end and inclosing a small quantity of mercury, is exhausted of air, the mercury vapor in the tube will carry the current when it is once started and it will become a source of light. In the Cooper-Hewitt lamp, Fig. 1, the mercury is held in the large bulb at one end of the tube and serves as the cathode. The anode is a small iron cup at the other end of the tube. Platinum wires sealed in the glass carry the current to the electrodes.

on the simplest form of the lamp the tube is tilted by pulling on the suspended chain until the mercury runs through the tube in a thin stream. This mercury connects the electrodes and starts the current. As soon as there is a break in the stream, an arc is formed, the mercury  vapor fills the tube and sustains the arc the full length of the tube when the mercury runs back .

The quality of the light is peculiar in that it contains no red rays. In uses in which the red rays are required, as in the judgment of colors, the lamp is supplied with a transforming reflector which converts a portion of the violet rays into red and improves the quality of the light for such purposes.