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

382 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,

Rh Hence Rh

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, Rh

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, Rh

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.