Note 38 — ON THE FUNDAMENTAL CONCEPTS OF ELECTROSTATICS.[26]

The jar in our experiment acts like an accumulator, being charged by a dynamo machine. The relation which obtains between the expended and the available work may be gathered from the following simple exposition. A Holtz machine H (Fig. 40) is charging a unit jar L, which after n discharges of quantity q and potential v, charges the jar F with the quantity Q at the potential V. The energy of the unit-jar discharges is lost and that of the jar F alone is left. Hence the ratio of the available work to the total work expended is

½QV/[½QV + (n/2)qv] and as Q = nq, also V/(V + v).

If, now, we interpose no unit jar, still the parts of the machine and the wires of conduction are themselves virtually such unit jars and the formula still subsists V/(V + Σv), in which Σv represents the sum of all the successively introduced differences of potential in the circuit of connexion.