Balancing magnetic force with gravity.

[Sammy268]

I have been reading ahead in my course from Griffiths textbook and I have a couple of questions. I found this solution online to a question: http://glennrowe.net/physicspages/2013/09/23/balancing-magnetic-force-with-gravity/

It says: A square loop is cut out of a thick sheet of aluminum. It is then placed so that the top portion is in a uniform magnetic field B, and allowed to fall under gravity.

The solution is fairly easy to understand, but I have a couple of questions.

What if the loop starts when the bottom edge is in line with the bottom of the magnetic field? In this case would B = 0? Is it possible to work out how long it would take to clear the field?

What would happen if the loop were to begin falling from above the field? Does this make the problem harder?

 

[256bits]

What if the loop starts when the bottom edge is in line with the bottom of the magnetic field? In this case would B = 0? Is it possible to work out how long it would take to clear the field?

The magnet provides B the B field, so no, B would not be =0.
If in line with the B field as soon as the loop falls any distance it has cleared, and the problem becomes as before.

What would happen if the loop were to begin falling from above the field? Does this make the problem harder?

Not really.
The current would be in the opposite direction with the bottom edge within the field as opposed to the bottom edge within the field.

What do you think would happen if both top and bottom edge are both within the field?