The Ideal Simple Dynamo
المؤلف:
GEORGE A. HOADLEY
المصدر:
ESSENTIALS OF PHYSICS
الجزء والصفحة:
p-403
2025-12-13
22
Under ideal conditions for a simple dynamo, the conductors would move in a uniform magnetic field. The nearest approach to this condition is obtained by using permanent magnets for the fields N and S, Fig. 1; a machine of this kind is called a magneto. By applying the laws for induced currents, we may determine the direction of the current produced by the dynamo. Suppose the single coil in Fig. 1 is turned from its vertical position, clockwise. At the beginning of the movement, the motion of the conductor is almost parallel to the lines of force so that there will be little cutting of the lines, and little induction; but the rate at which the lines of force are cut increases until the coil reaches the horizontal position, and then decreases, until, when the conductor has passed through 180° and is again vertical, the induction again becomes zero. As the upper branch descends, the direction of the induced current with reference to a person looking from N to S will be from the left toward the right as in Fig. 2. The induction in the lower part of the loop, as it rises, will be from right to left, and thus the two currents will join and flow in the same direction. Every time the coil passes through the vertical position, the direction of the current induced in it changes, so that there will be two alternations of current for every revolution.
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