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A copper ring is held horizontally and a...

A copper ring is held horizontally and a bar magnetic is dropped through the ring with its length along the axis of the ring (shown in the figure) will the acceleration of the falling magnet be equal to , greater than or less than that due to gravity?

Text Solution

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(i) When the bar magnet approaches the salenoid, magnetic flux linked wrth it increases and indaced emfis produced which opposes the motion of the magnet. W=mg weight of magnet acting in vertically downward direction F- Opposing force acting on the magnet. If a Acceleration produced in the magnet
`a=(mg-F)/(m)`
`a=g-(F)/(m)`
`rArr a lt g`
(ii) When magnet is weil inside the solenoid then no magnetie flux linked with the solenoid changes and hence no emfis induced.
So acceleration of magnet is equal to acceleration due to gravity in the absence of opposing force
(iii) When magnet moves out of the solenoid then again magnetic flux linked with coil changes (decreases) and hence emfis induced in it. As a result opposing force acts òn the magnet and `a=(mg-F)/(m) =g-(F)/(m)`
`rArr a lt g`
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