Physics Help Forum

Physics Help Forum (
-   Advanced Electricity and Magnetism (
-   -   Is EMF generated in this special loop of wire (

fogo57 Oct 5th 2012 12:33 PM

Is EMF generated in this special loop of wire
A square loop of wire is kept hanging upright and has 3 sides made of copper and the lower horizontal side made of iron. The loop has its surface normal to a uniform magnetic field B. The question is: If the loop is allowed to fall while fully immersed in this field B, will an EMF be generated in the loop? Why?

nullflux8 Oct 15th 2012 09:15 PM

My understanding is yes. It doesn't matter which is moving, either the field moves relative to the wire or vise versa a force will be realized. To add to your question. If the wire is moveing toward the field the force moves in a certain direction and when you move it away the direction of current changes as well. In a figure of 8 loop of wire the current moves clockwise on one loop of the 8 and counter clockwise in the other all the while you are moving either the loop or the wire, with or without an iron section to close the loop.


fogo57 Oct 16th 2012 05:06 AM

EMF in a special loop of wire. Discussion and CHALLENGE
Thanks for replying. First of all I wish to point out that the Magnetic field is uniform and HORIZONTAL. THe loop is not falling onto the magnet, but it is hanging upright and parallel to the magnets surface.
There are arguments for and arguments against the appearance of an EMF. I will give the "positive" argument. The two horizontal sides are made of magnetically different materials. The local B field inside the Fe side is about twice as strong than in the Cu side. A metallic bar moving in a magnetic field B will develop an EMF given by the product x*v*B, where x is the length, v is the velocity and B the field. Of course the Bs on both horizontal sides ( taken as the bars) are very different and the EMFs subtract each other, which would produce a net EMF force in the loop and a current flowing round it. I challenge the readers to point out a flaw in this argument ( of course doing the experiment would clarify everything!).

All times are GMT -7. The time now is 07:47 PM.

Copyright © 2016 Physics Help Forum. All rights reserved.
Copyright © 2008-2012 Physics Help Forum. All rights reserved.