ELECTRONIC PRINCIPLES - OD1647 - LESSON 1/TASK 1
By applying the lefthand rule to the dark half of the loop in
view B, figure 59, on page 87, one will find that the current
flows in the direction indicated by the heavy arrow. Similarly,
by using the lefthand rule on the light half of the loop, one
will find that current therein flows in the opposite direction.
The two induced voltages in the loop add together to form one
total emf.. It is this emf which causes the current in the loop.
When the loop rotates to the position shown in view D, figure
59, the action reverses. The dark half is moving up instead of
down, and the light half is moving down instead of up. By
applying the lefthand rule once again, you will see that the
total induced emf and its resulting current have reversed
direction. The voltage builds up to maximum in this new
direction, as shown by the curve in figure 59. The loop finally
returns to its original position, figure 59, view E, at which
point voltage is again at zero. The sine curve represents one
complete cycle of voltage generated by the rotating loop. All
the illustrations used in this topic show the wire loop moving
in a clockwise direction. In actual practice, the loop can be
moved clockwise or counterclockwise. Regardless of the
direction of movement, the lefthand rule applies.
If the loop is rotated through 360 at a steady rate, and if the
strength of the magnetic field is uniform, the voltage produced
is a sine wave of voltage, as indicated in figure 59.
Continuous rotation of the loop will produce a series of sine
wave voltage cycles or, in other words, an ac voltage.
As mentioned previously, the cycle consists of two complete
alternations in a period of time. Recently, the HERTZ (Hz) has
been designated to indicate one cycle per second. If ONE CYCLE
PER SECOND is ONE HERTZ, then 100 cycles per second are equal to
100 Hertz, and so on. Throughout this subcourse, the term cycle
is used when no specific time element is involved, and the term
Hertz (Hz) is used when the time element is measured in seconds.
(2) Frequency. If the loop in figure 59 makes one complete
revolution each second (1 Hz), increasing the number of
revolutions to two per second will produce two complete cycles
of ac per second (2 Hz). The number of complete cycles of
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