A laboratory manual of electrotherapeutics . ut by Bordier, these currents are distin-guished from ordinary alternating currents by three essen-tial properties, which are due to both the great frequencyand the high tension. ist. They cause remarkable inductive effects. The E. M. F. of induction near an inducing source isequal to the product of the intensity of the current by thefrequency. Let us suppose a frequency of 500,000 periodsper second and a mean current of 1 ampere. The E. in one turn would be the same as if a current of 100 OF ELECTROTHERAPEUTICS. amperes with a frequency of 50
A laboratory manual of electrotherapeutics . ut by Bordier, these currents are distin-guished from ordinary alternating currents by three essen-tial properties, which are due to both the great frequencyand the high tension. ist. They cause remarkable inductive effects. The E. M. F. of induction near an inducing source isequal to the product of the intensity of the current by thefrequency. Let us suppose a frequency of 500,000 periodsper second and a mean current of 1 ampere. The E. in one turn would be the same as if a current of 100 OF ELECTROTHERAPEUTICS. amperes with a frequency of 50 should circulate in roturns of wire. Thus it is seen that with high frequency theE. M. F. induced in a single turn would be a large solenoid the current induced in one turn is suf-ficient to illuminate by mutual induction a lamp of 8 voltsand 1 ampere. 2nd. Currents of high frequency, even though thecapacity be small, circulate as well in open as in closedcircuits, so that contact with only one pole suffices to givea current. Fig. 45. In fact, feeble as may be the capacity, the charge anddischarge, repeated hundreds of thousands of times persecond at a high potential, represent a notable mean cur-rent. It is this that explains the uni-polar currents, and thesparks that occur when any point on the solenoid istouched. In this case the body, constitutes an insulatedsurface which, at each oscillation, is charged with a verynearly constant quantity when it is at a certain distancefrom the solenoid. The corresponding charge of contrary sign should be 112 LABORATORY MANUAL found on the parts of the solenoid which are at thatmoment at a different potential. This explains why thesparks which are drawn from the solenoid are greatest atthe extremities and least midway. 3d. The resonant effects, which have been so beau-tifully shown by the experiments of Hertz, and which areextremely interesting to the physicist, but which have not,so far, been found to have any relationshi
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