_=293. Divided Circuits; Shunts.=_ The current divides at M P-B into two parts; one part may be called a _shunt_ of the other. The circuit is said to be _divided_; it has two branches. If the two ends of a wire be fastened to another as in Fig. 101, the circuit is also divided. When two or more conductors lead side by side from one point to another, they are called _parallel_ circuits; that is, the conductors are joined in parallel. As strong currents would injure delicate galvanometers, a small part only of the current may be allowed to pass through the galvanometer by using a shunt. Fig. 89 shows such an arrangement, in which most of the current passes through the shunt, S. There are many practical uses of shunts. [Illustration: Fig. 89.] =EXPERIMENT 115. To see what is meant by "short circuits."= _Apparatus._ About the same as in Exp. 114, Fig. 88. The astatic galvanoscope is not needed; in place of it provide a short piece of metal, such as a battery-plate, or even a jack-knife. _Arrange_ as in Fig. 88, but without A G. =294. Directions.= (A) With the current passing as described in Exp. 114 (A), take the reading of G V. (B) Lay the ends of the metal, or other thick conductor, upon M P-A and M P-B. Compare the new reading of G V with that in part (A). (C) Remove the conductor used to short circuit G V, take the reading in degrees, then touch M P-A to M P-B; watch G V. _=295. Short Circuits=_ are very apt to occur unless care is taken. Do not allow uninsulated wires to touch each other. As shown by the above experiment, practically the whole of the current may be side-tracked by a _shunt of low resistance_. A galvanic cell is short-circuited by connecting the plates directly by a wire or other conductor. CHAPTER XVII. ELECTROMOTIVE FORCE. _=296. Electromotive Force.=_ It has been stated that a galvanic cell has the _power_ to charge one of its plates positively and the other negatively; this power is called _electromotive force_, and, for short, E. M. F. is written. The E. M. F. of a cell depends upon the kinds of plates used and their condition, the chemicals used in the exciting fluids, etc. The greater the E. M. F. of a cell the greater its power to force the current through wires, etc. The E. M. F. of a cell does not depend upon the size of its plates, as will be seen by later experiments. _=297. Unit of E. M. F.; The Volt.=_ A certain amount of E. M. F. has been taken as the standard, and, in honor of Volta, it has been called the volt. The E. M. F. of the two-fluid cell used in Exp. 113 is not far from 1 volt. If a certain cell has the power to keep up twice the difference of potential between its terminals that the Daniell cell has, we say that it has an E. M. F. of about 2 volts. _=Voltmeters=_ are instruments to measure E. M. F. =EXPERIMENT 116. To see if the E. M. F. of a cell depends upon the materials used in its construction.=