Wireless Telegraphy and Telephony

WIRELESS TELEGRAPHY 29 series multiple, as shown in the accompanying diagram. This method of connecting distributes the load, and con- siderably lengthens the life of the battery. When the source of current supply is alternating, an in- duction coil may be operated as a transformer. Both in- duction coils and transformers are instruments for raising the voltage of the ordinary available current from a com- paratively low value, 6-220 volts, to a quantity (15,000- Fig. 30.—-If a magnet is suddenly plunged into a hollow coil of wire a momentary electric current will be induced in the coil. 20,000 volts), where it can properly charge the aerial and create a state of strain, or, as it is called in technical par- lance, an electro-static Held. Both the induction coil and transformer depend for their operation upon the principles of magnetic induction. In 1831, Michael Faraday, a famous English chemist and physicist, discovered that if a magnet be suddenly plunged into a hollow coil of wire, that a momentary current of electricity is generated in the coil. As long as the magnet remains motionless, it induces no current in the coil, but when it is moved back and forth, it sets up the currents. The source of electrical energy is the mechanical work