Page:A Treatise on Electricity and Magnetism - Volume 2.djvu/414

March 1868, p. 184. See also remarks on that experiment, by the present writer, in the number for May 1868.

VI. Electrostatic Measurement of Resistance. (See Art. 355.)

780.] Let a condenser of capacity C be discharged through a conductor of resistance R, then, if x is the charge at any instant,

Hence

If, by any method, we can make contact for a short time, which is accurately known, so as to allow the current to flow through the conductor for the time $t$, then, if $E_{0}$ and $E_{1}$ are the readings of an electrometer put in connexion with the condenser before and after the operation,

If $C$ is known in electrostatic measure as a linear quantity, $R$ may be found from this equation in electrostatic measure as the reciprocal of a velocity.

If $R_{s}$ is the numerical value of the resistance as thus determined, and $R_{m}$ the numerical value of the resistance in electromagnetic measure,

Since it is necessary for this experiment that $R$ should be very great, and since $R$ must be small in the electromagnetic experiments of Arts. 763, &c., the experiments must be made on separate conductors, and the resistance of these conductors compared by the ordinary methods.