[Electric engineering.] . carbon is very brilliant, almost ap-proaching sunlight. Violet rays are always present to some extent and give the arclight the well-known vio-let tinge that is oftenquite pronounced. Anarc between copper elec-trodes is of a greenishtinge, while an arc be-tween iron terminals isaccompanied by a bril-liant shower of 1- An arc may be formed between carbon and copper or carbon and platinum, thecarbon in both cases being used for the upper or positiveelectrode, as the terminals are often called, and the cop-per or platinum for the lower electrode. This arrange
[Electric engineering.] . carbon is very brilliant, almost ap-proaching sunlight. Violet rays are always present to some extent and give the arclight the well-known vio-let tinge that is oftenquite pronounced. Anarc between copper elec-trodes is of a greenishtinge, while an arc be-tween iron terminals isaccompanied by a bril-liant shower of 1- An arc may be formed between carbon and copper or carbon and platinum, thecarbon in both cases being used for the upper or positiveelectrode, as the terminals are often called, and the cop-per or platinum for the lower electrode. This arrange-ment has been used in a few isolated cases. For example,an upper positive carbon and lower copper electrode havebeen used in one form of locomotive headlight. It is im-portant when this arrangement is used to see that theupper carbon is connected to the positive pole of the dy-namo, so that the current flows from the carbon to thecopper. If it flows the other way, the copper or platinumelectrode will soon be burned 3. After the carbons have been separated for a timethey take on the appearance shown in Fig. 2. This repre-sents an open arc, or an arc formed in the open air, asdistinguished from one that is formed in a confined space § is ELECTRIC LIGHTING. where very little oxygen is present. The term arc came tobe used because of the small bow-shaped or arc-shaped flame thatmay be seen playing between thecarbon points. This flame is thearc proper and consists of incan-descent carbon vapor that con-ducts the current across frompoint to point. This flame, orarc, of carbon vapor acts in thesame way as a wire carrying acurrent. If a magnet is broughtnear it, the arc will be forced overto one side, and if the magnet isstrong enough, the arc will bestretched out until it is , the arc itself, under ordinaryworking conditions, will be sur-rounded by a magnetic field, andit is, no doubt, this field thatcauses the arc to assume the bowshape. The flame keeps shifting ar
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