. Electricity : its medical and surgical applications, including radiotherapy and phototherapy . obtained(Fig. 166). Physical Properties of Currents (see also pp. 98 and 99).—It is well tobear in mind the remarkable physical properties of these currents, viz.:They do not require a closed conductor or complete circuit for their 218 RULES FOR USING STATIC AND HIGH FREQUENCY CURRENTS transmission; they are transmitted as electric waves through the air,and will illuminate vacuum tubes held at a considerable distance;ordinary means of insulation are not applicable, and they will readilypass through
. Electricity : its medical and surgical applications, including radiotherapy and phototherapy . obtained(Fig. 166). Physical Properties of Currents (see also pp. 98 and 99).—It is well tobear in mind the remarkable physical properties of these currents, viz.:They do not require a closed conductor or complete circuit for their 218 RULES FOR USING STATIC AND HIGH FREQUENCY CURRENTS transmission; they are transmitted as electric waves through the air,and will illuminate vacuum tubes held at a considerable distance;ordinary means of insulation are not applicable, and they will readilypass through glass of considerable thickness; currents of extremevoltage (as high as 2,000,000) may pass through the body withoutpain or danger (p. 136). That currents of considerable strength may so pass through the bodymay be shown if two individuals will each hold one terminal of an incan-descent light while each is also connected with a terminal of a Teslacoil, when the current passes the lamp will be illuminated. If ananimal is placed within a large solenoid through which such a current Fig. 167. Hot-wire milliammeter for high frequency currents. is passing, powerful currents will be induced in the animal without painor discomfort (p. 263). Thus, if a man so placed holds the terminalsof an incandescent lamp, one in each hand, it will be illuminated. Different forms of coils give currents of different amounts of voltage,amperage, and frequency, according to the form of coil and source ofcurrent supply, viz., static machine or coil (pp. 100 and 213). Ingeneral it may be said that currents of a comparatively low voltage butgreater amperage are obtained from the DArsonval coil and primaryof the Tesla. The resonator attachment to the DArsonval coilincreases the voltage and lessens the amperage. The current from thesecondary of the Tesla coil is of still higher potential, while that from thehyperstatic transformer (p. 214) attached to a static machine is also HIGH FREQUENCY CURRENTS 219 h
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