Page 11 - Electrical Equipment Handbook _ Troubleshooting and Maintenance
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FUNDAMENTALS OF ELECTRIC SYSTEMS
1.10 CHAPTER ONE
FIGURE 1.10 A loosely wound solenoid.
FIGURE 1.11 A solenoid of finite length. The right end, from which
lines of B emerge, behaves as the north pole of a compass needle does. The
left end behaves as the south pole.
Figure 1.13 shows another experiment in which when the switch S is closed, thus estab-
lishing a steady current in the right-hand coil, the galvanometer deflects momentarily.
When the switch is opened, the galvanometer deflects again momentarily, but in the oppo-
site direction. This experiment proves that a voltage known as an electromagnetic force
(emf) is induced in the left coil when the current in the right coil changes.
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