Physics HSC 2021 (1 Viewer)

[krypticlemonjuice]

Can someone please explain this question. I get that eddy current form on both sides. But how do we determine their direction and the resultant force on the magnet??

 

[liamkk112]

one way to think about it is newtons 3rd law. lenz's law says that change in flux needs to create a current that opposes the flux change cuasing induced current. bc the magnet is moving to the right it has to experience a resistive force to the left. The only way this can happen is if the copper block is being pushed to the right (newtons 3rd law)

 

[wizzkids]

Simple.
Apply Lenz's Law.
The eddy currents in the copper block will respond in such a manner as to oppose the change that caused it.
The cause is the relative motion of the magnet.
Therefore the induced eddy currents will try to reduce the relative motion of the magnet.
If the copper block was placed on a zero friction surface, it would slide to the right, and attempt to follow the motion of the bar magnet.
Hence, the force on the copper block is to the right.
[btw, this is also the same electromagnetic principle as the AC induction motor]