An elementary book on electricity and magnetism and their applications . Fig. 88. — Coil rotating between poles of electromagnet and a single loop con-nected to slip rings. is generated in the coil an alternating current, which reversesits direction twice in every revolution. Moreover, it will beseen that the induced starting at zero goes up to a maxi-mum and then backto zero in the firsthalf turn; then itreverses, goes to amaximum in the op-posite direction andfinally back to zero. LL~^ P0SITI0N 0F L00P1N DEGREES rpii -it r Fig. 89. — Curve to show relation of induced The induce
An elementary book on electricity and magnetism and their applications . Fig. 88. — Coil rotating between poles of electromagnet and a single loop con-nected to slip rings. is generated in the coil an alternating current, which reversesits direction twice in every revolution. Moreover, it will beseen that the induced starting at zero goes up to a maxi-mum and then backto zero in the firsthalf turn; then itreverses, goes to amaximum in the op-posite direction andfinally back to zero. LL~^ P0SITI0N 0F L00P1N DEGREES rpii -it r Fig. 89. — Curve to show relation of induced The induced to position of loop, reaches its maxi-mum when the coil is horizontal, because in this position thewires AD and BC are cutting lines of force most rapidly. Thisis illustrated by the curve shown in figure 89. Machines which. 144 ELECTRICITY AND MAGNETISM are built to deliver alternating currents are called alternatorsor alternating-current (a-c.) generators. Problems 1. A coil of one turn includes 5,000,000 lines of force within itsarea when the plane of its face is at right angles to the lines. If it isturned over at the rate of 1200 revolutions per minute, what will bethe average of the voltage induced during each half revolution?(Hint. — Each side of the coil cuts all the lines twice in a revolution.) 2. If the coil in problem 1 had 25 turns, what would be the averagevoltage induced? 3. One side of a large coil of wire having 100 turns cuts through afield of ,000 lines of force at an average rate of 2400 times perminute. What is the average voltage developed? (Hint. — Theturns are in series.) 4. A coil of fifty turns with two active sides cuts through 5, of force at a speed, during the moment considered, of 2400 timesper minute. The resistance of the coil is of an ohm and the
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectmagnetism, bookyear19
