12 physics, state and explain the principle , construction , working of ac generator
Answers
■ Construction :
● Armature coil .....
a large number of turns of insulated copper wire wound around on a soft iron core in rectangular shape forms armature coil ABCD
● strong magnet....
the coil is placed between the two poles of a strong magnet to provide strong magnetic field
● slip rings .....
the ends of coil are connected to the two slip rings R1 and R2
● brushes ...
two carbon brushes B1 and B2 are used to press the rings R1 and R2 respectively . the outer ends of two brushes are connected to galvanometer to show the flow of current ..
■ working :
● the armature coil is rotated in the magnetic field provided by strong magnet
● the axel attached to the two rings rotate in such a way that arm AB of coil moves upward and arm CD moves downwards . thus coil ABCD rotates in Clockwise direction
● the induced current is produced which flows in the direction ABCD . thus current in the external circuit flows from brush B2 to B1 .
● after completing half rotation ,arm AB starts moving down while CD starts moving up . as a result direction of induced current in both the arm reverses and flows in the direction DCBA . thus current in external circuit flows from brush B1 to b2 .
● thus polarity of induced current in respective arm changes after every half rotation
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