Rheostat, Wheat stone's

This apparatus consists of two cylinders, one, A, made of bra , the other, B, of wood, with a spiral groove. At its end is a copper ring a. A fine bra wire has one end attached to this ring. Its other end is fastened at e, and it is wound as shown; n and o are binding screws connected, one with the cylinder-ring a, the other with the bra cylinder, A. The current entering at o, traverses the wire on B, as there the windings are insulated by the grooves, thence it pa es to m and by A, whose metal short circuits all the wire on it, to the binding-post n. The handle, d, is turned one way or the other to regulate the length of the wire through which the current must pa . On each cylinder there is a square head, one of which is shown at c, so that the handle can be shifted from one to the other as required; to A if the wire is to be wound on that cylinder, to B if the reverse is desired. IMG:8956969607833025625_473F297.jpg: Fig. 297. WHEAT STONE'S RHEOSTAT. 473   STANDARD ELECTRICAL DICTIONARY.