Editorial Feature

Carbon Arc Lamp - Properties and Applications

Arc lamps are a category of lamps that produce light by an electric arc (also known as a voltaic arc). The lamp consists of two electrodes that are separated by a gas. The lamp is named based on the type of gas that is used in the arc. The first arc lamp consisted of two carbon electrodes that were simply suspended in air, through which current was passed.

The electric arc produces light by the sparking of a high current between two electrodes. The first arc lamp was invented by Sir Humphry Davy in the early 1800s. This article will provide details on the working, construction, and applications of the carbon arc lamp.

Working

The carbon arc lamp consists of two carbon electrodes suspended in free air. In order to ignite an arc lamp, the electrodes are touched together. This generates a low voltage to strike the arc. The rods are slowly withdrawn, the electric current between the electrodes heats, and this maintains an arc through the gap. The heat and current together generates light.

The color of light emitted by these lamps varies with the electrical characteristics, temperature, and time.

Construction

In a carbon arc lamp, the electrodes are made of carbon. They are suspended in air. Current is passed through the electrode using a battery or a dynamo. The carbon rods need to be replaced often, as they tend to burn away. Therefore, solenoids are used in place of carbon electrodes.

Applications

Carbon arc lamps have inherent disadvantages, which have made their usage obsolete. Some of the applications for which these lamps were used in the past are listed below:

  • Early motion pictures
  • Searchlights
  • Projectors
  • Followspots

Sources and Further Reading

  • Arc Lamp – Princeton University
  • Arc Lamp – Florida State University

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