Fig. 1,042.—Diagram showing operation of variable gap arc breaker used on heavy duty lightning arresters. When a lightning discharge passes across the gap to earth, the dynamo current follows it and energizes the magnet M, which attracts the short arm of the double lever, thus quickly jerking the terminal B away from C. The wider air gap thus interposed between B and C greatly increases the resistance which breaks the arc.
Ques. How is this done?
Ans. There are several methods, of which may be mentioned the variable gap method described in [fig. 1,042], and the magnetic blow out method shown in [fig. 1,043].
Ques. Where should lightning arresters be placed?
Ans. They should be placed as near as possible to the point where wires enter a building, and in an easily accessible place away from combustible material.
Ques. What should be avoided in installing lightning arresters?
Ans. Kinks and sharp bends in the wire running from the outdoor lines to the arresters and from arresters to ground should be avoided as far as possible.
Ques. Why should kinks and sharp bends be avoided?
Ans. Because they offer resistance to the lightning discharge.