Science and Industry Volume 6

Science and Industry Volume 6

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1901 edition. Excerpt: ...machines. Dynamo-electric machines may be built so as to generate either direct current or alternating current. When they generate alternating current they usually go by the name of altemators. An alternator is, as a rule, simpler in construction than a direct-current dynamo, because the latter has to have a commutator and a number of brushes, whereas an alternator does not require any commutator, and can in fact be built without any-moving wire at all. In the first place, before we can have an alternating current we must have an alternating pressure or E. M. F. to set up that current. It is far better, therefore, to look upon an alternator as a machine for setting up an alternating pressure than as a machine for generating alternating current. The current is merely a result of the pressure. view of the coil and pole piece; note, in passing, that the inside diameter of the coil is a little larger than that of the pole piece. Suppose, now, that the coil is in the position shown in the figure and that it is suddenly pulled off to one side, in the direction indicated by the arrow. If the pointer of the voltmeter be watched closely it will be seen to swing over and then come back to rest again as the coil is pulled away from the pole. We have pulled the coil across the lines of force, or have made the turns of wire to cut lines of force, and as long as this cutting process continues an E. M. F. will be generated. Another way of looking at it is that the number of lines of force or the amount of magnetism passing through the coil has been made to decrease, and anything that causes the amount of magnetism threading a coil to increase or decrease will set up an E. M. F. in the coil. If the coil is now moved back to the position shown in more

Product details

  • Paperback | 284 pages
  • 189 x 246 x 15mm | 513g
  • United States
  • English
  • black & white illustrations
  • 1236981324
  • 9781236981325