- #1

sgstudent

- 739

- 3

By Fleming's Left hand rule, there is an induced forced (IF in diagram) at the downwards position at the armature AB. Thus, by Fleming's Right hand rule there is an induced current (IC in diagram) which opposes the current that is supplied by the battery (C in the diagram). As the induced force is directly proportional to the 'net' current flowing through AB, the induced force slowly decreases. This is because the induced current will keep increasing since there is a net moment about P which means there is an angular acceleration. After a while, there will be no more net moment as the induced current keeps on increasing which in turn causes the induced force to decrease. Since net moment about P=IF*l-friction*l, so IF*l >0 hence, the induced current is always lesser than the current supplied by the battery. This causes the 'net' current flowing across the circuit to be smaller than the inital current when the induced current in the opposite direction has not increased yet.

The image: http://i.imgur.com/2pkmq.png

Is this correct? Thanks for the help