Min's Lazo.—This law is singularly in accordance with experimental results. It assumes that the electromotive force for a particular galvanic pair is constant., and that the strength of the current it produces is the quotient which results from dividing it by the resistance of the circuit. This resistance arises from two sources, the first being the resistance within the cell offered by the exciting liquid, and the second the interpolar resistance. If e represent the electromotive force; 1, the resistance within the cell; w, the interpolar resistance; and S, the strength of the current, or the quantity of electri city actually transmitted, the statement of the law for one couple stands thus S: = 6 .
+ 20 The application of the law in a few particular cases will best illustrate its meaning. If we increase the number of cells to 71, we increase the electromotive force is times, and at the same time we increase the liquid resistance n times, for the current has is times as much of it to travel, then S = 7t . If w be small compared with n/---that is if /±w the external connection be made by a short thick wire—it may be neglected, and so ne e =S Tt. i = This shows that one cell gives in these circumstances as powerful a current as a large battery. But if n1 be small with respect to w—as in the interpolar circuit of ne an electric-telegraph battery—nl may be neglected, and S = Here we learn that the strength of the current increases directly as the number of cells. We may learn from
the same that the introduction of the coil of long thin wire of a galvanometer into such a circuit, introducing but a comparatively small increase of resistance, causes a very slight diminution of the current strength. If, again, we increase the size of the plates of a galvanic pair is times, the section of the liquid is proportionately increased, so that whilst the electromotive force remains the same, the cell resistance diminishes n times; therefore S = /d- or S = 710 If the exterior resistance is small, nt may YL be neglected, and S = and the strength is thus shown to increase is times. These are only a very few of the conclusions arrived at by this law. With the aid of a tangent galvanometer, which gives the value of S expressed in absolute magnetic units, or centimeters of voltameter gas, we ascertain e and 1 for any pair. By making two obser vations with two wires of known resistance separately included in the circuit, we have two simple equations with two unknown quantities, from which e and 1 can be easily found. In doing so we must adopt a unit of resistance. The unit proposed and deter mined by the British association, the 13.A. unit, or the ohm, is the only one now used in this country. The resistance of the liquid of the pair would be expressed in units of this, and the electromotive force:in absolute units or centimeters of gas, with a circuit offering a unit of resistance.