Why Does EMF Change as a Magnet Passes Through a Coil?

[jsmith613]

Homework Statement

If I take a magnet and drop it though coil then the graph would have an increasing voltage until a maximum and then a reducing emf (until 0) and then a further reducing emf until a minimum and then an increasing emf again

graph looks like this: http://www.djb.co.uk/Graphics/Physics/Teachers/magnet.gif

Remember the magnet remains wholy in the coil for several seconds.

Questions:
1) why does the EMF gradually increase then decrease until 0 then decrease further and then increase again??


2) if the magnet remained wholly in the coil for a while will any voltage be induced? why?

Homework Equations

no questions

The Attempt at a Solution

1) well if the magnet falls straight through the polarity changes but this also confuses me. how can it change if the magnet is falling through without chaging direction?

 

[anathema]

2) Yes, voltage will still be induced because the changing magnetic field created by the falling magnet will still induce a current in the coil, regardless of the duration of time the magnet remains in the coil. The induced voltage will decrease as the magnet falls further away from the coil, resulting in the decrease and then increase in EMF shown in the graph. This phenomenon is known as Faraday's law of induction. The changing magnetic field induces a current in the coil, which in turn creates a magnetic field that opposes the original change in the magnetic field, leading to the decrease in EMF. As the magnet moves further away from the coil, the induced current and magnetic field weaken, resulting in the increase in EMF again. This process repeats until the magnet reaches the bottom of the coil.