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Re: [Phys-l] Figuring Physics in the March TPT The Physics Teacher



Hi.

So I have a loop of wire parallel to Earth. I drop a magnet through the loop. The magnet is lined up with N on top and S on bottom (so S goes through the loop first).
If I were to qualitatively graph the flux vs time, and current vs time I'd get (would I get?):

Part 1: S is far away to S / N magnet bisect the loop.
Flux goes from zero (or really really small) to a maximum (when S pole is in center of loop) and then back to zero when the magnet is bisected by loop (weakest part of magnetic field).

Part 2: S / N bisect loop to N is far away.
Flux goes from zero to maximum (when N pole is in center of loop) to zero when N is really far away.

When this is graphed, is this like a 2 humped camel with both humps up, or is this more like a sine curve with one hump up and one hump down?
How would we get the up vs down (+ vs -) from Flux = BA (where would the negative come from)?
When we rotate a magnet in the place of a coil, the angle changes and rotates through the 2rpi. The cosine would give us +/-. Since we are not rotating, it would appear that we could choose if we want it to be + or - the entire fall.

So-
Would flux be a two humped camel?
Would the two humps be both up, or could you explain how to make one up (+) and one down (-)?

Sorry to bother, I'm ashamed to admit I don't know the answer. I've loaned out my favorite references (no, not Feynman yet... this summer).

Thanks for your help.



Paul Lulai
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