Generator principal and Simple loop generator

        Generator principal:

• An electric generator is a machine that converts energy into electrical energy.
• Whenever magnetic flux is cut by a current carrying conductor then e.m.f. is induced in the conductor and the conductor circuit must be closed.
• The direction of induced e.m.f. (and hence current) is given by Fleming's right hand rule. Therefore , the main components of a generator are:

                                          a) A magnetic field

                                          b) Conductor or a group of conductors

                                          c) Motion of conductor w.r.t. magnetic field

Simple loop generator:

•         Consider a single turn loop ABCD
•        The ABCD loop rotates clockwise direction in a uniform magnetic field with a constant speed.  
•       As the loop rotates , the flux linking the coil sides AB and CD changes frequently. Hence the e.m.f. induced in these coil sides.
•       When the loop ABCD is just parallel to faces of field magnets N and S , the flux linking with the loop is maximum but the rate of change of linking flux is zero so induced  e.m.f. is zero when the loop in this position.This position of the loop is known as neutral position. In the position of the loop shown in Fig(a).

                  

                                                                                                                                         

•       When loop ABCD starts cutting across the field, first it slowly and then gradually increases rate.
•       So the magnitude of induced E.M.F in the loop is gradually increases as the loop moves.
•       During this period the loop rotates through π/2 radians or 90°.
•       The direction of emf induced in the coil , as given by Fleming's right hand rule is form B to A and form D to C. In the position of the loop shown in fig(b).

  

•      When the ABCD loop rotates between between π/2 radians and π radians or (90° to 180°).
•      In the 2nd quarter , magnetic field gradually decreases , so rate at which the conductors cut across the magnetic field gradually decreases as the loop moves.
•      So induced E.M.F. is zero. In the position of the loop shown in fig(c).

                                                                                                                                          

•      When the ABCD loop rotates between rotates between  π and 3π/2 radians or (180° to 270°)
•      In the 3rd quarter , magnetic field gradually increases , so rate at which the conductors cut across the magnetic field gradually increases as the loop moves.
•      So the magnitude of induced E.M.F. in the loop is gradually increases.
•      The direction of E.M.F induced in the coil , as given by Fleming's right hand rule is form A to B and form C to D. In the position of the loop shown in fig(d).

•      When the ABCD loop rotates between  3π/2 and 2π radians or (270° to 360°)
•      In the 4th quarter , the induced E.M.F. decreases as the coil moves and becomes zero.
•      At this instant the loop comes to its absolute original position. In the position of the loop shown in fig(e).

•     The E.M.F thus generated in a loop is of the form shown in fig (f).