1. Consider initially the coil, positioned
in such a way that magnetic flux passes
through it. When the coil is at rest in vertical
position, with side A of coil at top position
and side B at bottom position, no current will
be induced in it. Thus current in the coil is zero at this position.
2. When the coil is rotated in clockwise direction, current will be
induced in it and it flows from A to B. During the first quarter of rotation,
the current increases from zero to a maximum and reaches peak value
when the coil is in horizontal position.
3. If we continue the rotation of coil, current decreases during the
second quarter of the rotation and once again becomes zero when coil
comes to vertical position with side B at top A at bottom position. During
the second part of the rotation, current gener-ated follows the same pattern
as that in the first half except that the direction of current is reversed.
(see fig.-17(b))
• Can you guess the
reason for variation of
current from zero to
maximum and vice-versa
during the rotation of coil?
• Can we make use of this
current? If so, how?
Let us find out.
As shown in fig.-17(a)
the ends of the coil are
connected to two slip
rings. Two carbon brushes
arranged in such a way that they press the slip rings to obtain current
from the coil. When these brushes are connected to external devices like
TV, radio, we can make them work with current supplied from ends of
carbon brushes.
The current obtained by this process changes its direction
alternatively for each half cycle as shown in figure 17(b).
This current is called alternating current (AC) in which, the direction
(see fig.-17(b))