Please help with understanding Lenz's Law

[leeanderthal]

Hi All,


For a long time I thought that I had a handle on Lenz but I never really did any experiments to actually visualize how it works.  My test:  I passed a coil through a magnetic field and noted the polarity of current produced with a galavanometer.  I replaced the galvanometer with a battery and connected to the coil using the same polarity that the galvanometer indicated.  To my surprise the coil attracted the magnet.  I thought that the field induced in the coil by the magnet was supposed to oppose the field of the magnet.  What am I missing here?  Is it a brain cramp, altzheimers or am I living in Bizarro world?


Any help would be appreciated.

[leeanderthal]

After sleeping on it, I think I'll answer my own question.  I am living in Bizarro world!  For example, everything taught in this video is bass ackwards.  http://www.youtube.com/watch?v=_ceHDC-f2Tk
When trying to measure the effects of Lenz's law in an open circuit the effects won't be apparent.  The only work done in that video was the prof moving 2 needles on 2 ammeters.  In fact he did create an opposing current which countered his measured current and it caused him to do work.  Work equal to the effort to move those 2 needles, plus a minute extra for wire resistance.  I'll bet if he replaced his ammeters with batteries, all of his supposed attractions and repulsions would be reversed.

[conradelektro]

Why not start with the "normal" explanations before going into the Bizzaro world? Bizzaro is mostly confusion.

http://en.wikipedia.org/wiki/Lenz%27s_law

The video  http://www.youtube.com/watch?v=_ceHDC-f2Tk is very clear and says it all.

Adding a battery to the experiment will combine "a magnet caused by a current (from the battery) in the coil" with "the magnet put into the coil by hand". And it is then more difficult to analyse the combined effect. The "magnet caused by the current" will be fairly strong because a huge current will flow from the battery through the coil due to the rather low resistance of the coil.

Most confusion comes from looking at "combined effects" which are not that easy to analyse.

One might as well understand that:

http://en.wikipedia.org/wiki/Electromagnetic_induction

Greetings, Conrad

[leeanderthal]

Sorry about adding to the confusion but this "science" seems to be riddled with it.  Conventional electron flow vs. actual electron flow.  Nomenclature of the poles..isn't that pretty much arbitrary?  Is the north end of a compass needle north or is it or is it north seeking thereby making it south?  Topsy turvy = bizarro ...not so confusing... just upside down.


Thanks for you input Conrad.  It seems to me,  that the direction of the current induced by the magnet in the coil is not the direction of the Lenz force current.  I agree with you that these combined effect are not easy to analyse.  When the same direction of current flow that was caused by the magnets induction is duplicated by a source (battery) the mechanical forces depicted in the video cited are opposite.  The Lenz force serves to "in effect" momentary increase the resistance of the coil while the field is expanding.  I think of it as salmon (electrons) swimming upstream (countercurrent).

[tinman]

Hi All,


For a long time I thought that I had a handle on Lenz but I never really did any experiments to actually visualize how it works.  My test:  I passed a coil through a magnetic field and noted the polarity of current produced with a galavanometer.  I replaced the galvanometer with a battery and connected to the coil using the same polarity that the galvanometer indicated.  To my surprise the coil attracted the magnet.  I thought that the field induced in the coil by the magnet was supposed to oppose the field of the magnet.  What am I missing here?  Is it a brain cramp, altzheimers or am I living in Bizarro world?


Any help would be appreciated.

How exactly did you get a polarity from your meter?,when passing a magnet over a coil(or visa versa) gives you an AC current,not DC.