Lessons in elementary physics / by Balfour Stewart.

Balfour Stewart

Date:: 1895

Credit: Lessons in elementary physics / by Balfour Stewart. Source: Wellcome Collection.

479/502 page 459

$the positive pole, which is u.sually placed uppermost, so that the bulk of the light passes directly down from the luminous crater. As the light continues the carbons are disintegrated, most of the carbon being sublimed, but a little combines with oxygen of the atmosphere to form carbon monoxide. When the gap between the carbons becomes of a certain distance the light would be extinguished if some arrangement were not provided for bringing the carbons together again. This may be effected bj- special electrical and mechanical contriv- ances such as that .seen in Fig. 156, which illustrates the 1 general principle of many modern lamps. The current enter- ing at the positive terminal divides into two parts, the gre.ater portion passing round the thick wire of the lower coil s called the senes coil, and thence to O and down the carbon rods from .\ to B. The effect of the current in the helix is to cause an iron core c to be attracted within the coil, the end of the lever pivotted at o is depressed, the upper carbon is raisctl, and the irc is produced. This is c.dled striking the arc. As the dis- tance between the ends of the carbons increases, less current passes round the lower coll and more round the upper one, which consists of a number of turns of lino wire and is called the shunt coil, with the rc.sult that the upper iron core C is more strongly attracted and at length overcomes the effect of the$

Lessons in elementary physics / by Balfour Stewart.

Licence and re-use

Contents