21. The necessary high voltage, typically 10, 000 volts, is supplied by an induction coil or transformer. 22. The early Swedish-designed devices used rechargeable batteries, which were charged by an induction coil from the outside. 23. Induction coils were used to provide high voltage for early gas discharge and Crookes tubes and other high voltage research.24. A nozzle releases a puff of gas which spreads across a flat spiraling induction coil of wire about 1 meter across. 25. The induction coil can be placed outside thermal insulation, so it operates at low temperature and has a long life. 26. In this process, the current to weld the pipe is applied by means of an induction coil around the tube. 27. :: : : : Two problems : 1 ) the induction coil would still be going at the same frequency! 28. On the outside of the patient's scalp rests the corresponding induction coil and an antenna that sends the receiver. 29. The engine operates contact breaker points, which interrupt the current to an induction coil ( known as the ignition coil ). 30. His first transmitter consisted of an induction coil connected between a wire antenna and ground, with a spark gap across it.
