More induction questions (1 Viewer)

[superbird]

Just want to confirm something. There is this experiment where a magnet is placed above a circular disk. As you move the magnet the disk turns. Just wanted to know what pole does the disk have if I place a North magnet above it.
Also if I place a north magnet through a coil, does the coil possess a north pole?

And finally, there is an experiment where you have a pendulum and if you place a magnet in front of it, it would supposedly stop the pendulum from moving. could somebody explain what exactly is taking place here. why is it that they recommend copper wire for this experiment as its more effective for stopping the pendulum? im sure its something to do with eddy currents...

 

[Jase]

The first one, im not quite sure what you mean by, moving the magnet and turning it. I think you're talking about eddy currents induced in the disk, so yes, a north pole is on the disk if a north pole is moved vertically downward. If you move the magnet sideways, then a north pole will be infront of its motion opposing it, and a south pole behind it, attracting it.. all due to eddy currents.
If you move a north through a coil, a north will be produced right on the edge to oppose the incoming magnet, so if that's what you're asking then yes, it does.

You connect a copper wire to the pendulum to to create a circuit, in order for a current to flow. When the pendulum approaches the magnet, eddy currents are induced in the surface such that it will oppose the motion towards the magnet.. as in, from Lenz's law and Faraday's , as the pendulum moves in to the magnet, an emf is induced right? and this emf will create north poles and south poles to try and stop moving into the magnet's field. So the currents that produce the opposing field are eddy currents. And without the copper, eddy currents wouldn't flow.

 

[superbird]

thanks for the quick reply. ill rep u for that

basically its all got to do with eddy currents. im still a little bit confused about the circular disk tho but seeing how i understand the concept of eddy currents i should be safe.

edit: dammit i cant rep u since i already hav