Question

state Fleming's right hand rule explain the principle and construction of ac generator

Answer 1

Answer:

Fleming's right hand rule :

Stretch the thumb, forefinger and middle finger of right hand so that they are perpendicular to each other. If the forefinger indicates the direction of the  magnetic field and the thumb shows the direction of motion  of conductor, then the middle finger will show the direction  of induced current.

Principle and construction of AC generator:

An electric generator, as shown in Fig. 13.19, consists of a rotating

rectangular coil ABCD placed between the two poles of a permanent  magnet. The two ends of this coil are connected to  the two rings R1  and R2

. The inner side of these  rings are made insulated. The two conducting  stationary brushes B1  and B2

are kept pressed  separately on the rings R1  and R2

, respectively. The  two rings R1  and R2  are internally attached to an  axle. The axle may be mechanically rotated from  outside to rotate the coil inside the magnetic field.  Outer ends of the two brushes are connected to  the galvanometer to show the flow of current in the  given external circuit.  When the axle attached to the two rings is  rotated such that the arm AB moves up (and the

arm CD moves down) in the magnetic field produced  by the permanent magnet. Let us say the coil ABCD  is rotated clockwise in the arrangement shown in Fig. 13.19. By applying  Fleming’s right-hand rule, the induced currents are set up in these arms  along the directions AB and CD. Thus an induced current flows in the  direction ABCD. If there are larger numbers of turns in the coil, the current  generated in each turn adds up to give a large current through the coil.  This means that the current in the external circuit flows from B2  to B1

.

After half a rotation, arm CD starts moving up and AB moving down.  As a result, the directions of the induced currents in both the arms  change, giving rise to the net induced current in the direction DCBA.  The current in the external circuit now flows from B1  to B2

. Thus after  every half rotation the polarity of the current in the respective arms  changes. Such a current, which changes direction after equal intervals  of time, is called an alternating current (abbreviated as AC). This device  is called an AC generator