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Elaborate the standard construction details of AC generator. |
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Answer» SOLUTION :CONSIDER a rectangular coil of, N turns kept Figure(a). The coil rotates in anti-clockwise direction with an angular velocity `OMEGA` about an axis, perpendicular to the field. ii. At time = 0, the plane of the coil is perpendicular to the field and the flux linked with the coil has its maximum value `Phi_(m)=BA` (where Ais the area of the coil). iii. In a time t seconds, the coil is rotated through an angle `theta(=omegat)` in anti-clockwise direction. In this position, the flux linked is `Phi_(m)COSOMEGAT,` a component of `Phi_(m)` normal to the plane of the coil (Figure(b)). The component parallel to the plane `(Phimsinomegat)` has no role in electromagnetic induction. Therefore, the flux linkage at `NPhi_(B)=NPhi_(m)cos omegat`  iv. According to Faraday's law, the emf induced at that instant is `epsi=(d)/(dt)(NPhi_(B))=-(d)/(dt)(NPhi_(m)cosomegat)` =-NPhi(-sinomegat)omega` =NPhi_(m)omegasinomegat` v. When the coil is rotated through 90o from intial position, `sinomegat=1.` Then the maximum value of induced emf is `epsi_(m)=NPhi_(m)omega` `epsi_(m)=NBAomega""" SINCE "Phi_(m)=BA` vi. Therefore, the value of induced emf at that instant is then given by `epsi=epsi_(m)siomegat.` vii. It is seen that the induced emf varies as sine function of the time angle `omegat.` The graph between induced emf and time angle for one rotaion of coil will be a sine curve (Figure) and the emf varying in this manner is called sinusoidal emf or alternating emf. |
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