i jus want to clarify a doubt that in dc generator usually magnets are stable and the armature shaft is allowed to rotate.what ll happen if we do in reverse that making shaft as stable and allowing magnet to rotate
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It will definitely induce emf in that case too. Only that the commutator has to be designed accordingly. And the direction of induced emf will be as obtained by Fleming's right hand rule.
wat will be the direction of emf if the magnets are allowed to rotate in anti clock wise direction????????? can u give a brief on the design of commutator for this case???
Direction of emf:
It will also depend on the pole under which the conductor is present at that specific time. Magnets rotating anti-clockwise is effectively same as the conductor rotating clockwise. We need to consider the direction of rotation of conductor just because Fleming's right hand rule was framed based on the motion of conductor and that is what we use to find the direction of induced emf in a generator.
Design of commutator:
Commutator is used to actually convert the generated alternating voltage to direct form. Here, since the casing of the generator(where the magnets are fixed) is rotating, there has to be some method to take the current out with ease. What I think of is a slip ring setup between the commutator output and load. The output from commutator inside the casing will be passed on to sliprings outside the casing which are also fixed on the shaft from which the output can be taken through brushes. There could be other, better, ideas.