Physics Question

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Susan
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Physics Question

Post by Susan »

Does anybody know the formula to find the force exerted by an electromagnet?

The questions goes:
If an electromagnet of 240 turns creats a force of 5.50 N when connected to a 9.00 V battery, how many turns on a similar coil of the same resistance are needed to produce a force of 22.0 N when connected to a 6.00 V battery?


I know I've seen a formula for this, but I have looked through every page of my textbook and online and I can't find it anywhere.
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Fras
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Post by Fras »

I know it has something to do with the rule of thumb. at least the direction of the force.. just how to get the power.. I can't remember. been a while :)
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Axtech
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Post by Axtech »

I have no idea how to figure that out. :wtf:
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Susan
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Post by Susan »

By rule of thumb, you must mean the right hand rule. That I do know, but it just tells you the direction of the force, not the actual amount of it.

Bah. I'm getting frustrated
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Post by Axtech »

We did direction of force (right hand rule), but we never did how much force.

Is this like a review question? If so, ask your teacher on monday (if, like me, you have school on monday) how to do it.
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Post by Susan »

My teacher's a bit of a nut, and the exams tomorrow. He never taught us this, and it came up on our unit test and the last few practice exams he gave us.

I just want to be prepared incase it shows up.
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Axtech
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Post by Axtech »

Do you guys get a "cheat sheet" for physics? We get one page front and back of anything we want.

I've got all of the equations from the course on the front (and one for your question is definately not there), and a bunch of theory/laws on the back. I'm going to slaughter this exam!
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Post by happening fish »

Go Robbo! Woo!
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Post by starseed_10 »

bleh. we didnt even learn about magnetism ....but then we lost 3 weeks worth of time cause of a bad student teacher. our teacher had to re-teach the whole chapter.

anyway, i have a fricking huge bio exam on wednesday and tonight and tomorrow are taken by my final drafting project due on tuesday. I pretty much havent started studying and my parents dont want me pulling all nighters before my exams. when the hell do i study?
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Post by superrgirll »

i hate physics. :(
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Post by Susan »

Rob

We get formula sheets, but ours can only be one-sided, formulas only. No written words and things like that.

Two sides with theories and lawa would make it way too easy.

Realisitcally speaking, it makes sense. If you were in a lab doing physics experiments or tests, you would probably have some resources with you refer to.
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Post by sandsleeper »

my uncle, the physicist came up with the answer 1440.

he doesn't remember the formula off the top of his head but he did it through proportionality.
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Post by joe_canadian »

I have that formula in my physics book, but it's not with me, sorry.
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Post by Axtech »

su7an wrote:Realisitcally speaking, it makes sense. If you were in a lab doing physics experiments or tests, you would probably have some resources with you refer to.


Exactly!
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Post by starseed_10 »

sandsleeper wrote:my uncle, the physicist came up with the answer 1440.

he doesn't remember the formula off the top of his head but he did it through proportionality.



:nod: that makes sense, i dont know if anyone can follow this but:


If an electromagnet of 240 turns creats a force of 5.50 N when connected to a 9.00 V battery, how many turns on a similar coil of the same resistance are needed to produce a force of 22.0 N when connected to a 6.00 V battery?


the battery in the second system is reduced by 1/3rd. so you reduce the force in the first system by a third to see what it would be under a 6 V battery.

one third of 5.5 = 3.667

so: under a magnet of 240 turns with the 6 V batter you get 3.667 N
22N / 3.667N = 6

so: the second system's magnet has 6 times as many turns = 1440.
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Post by Susan »

Ahhh! I see it now!

Thanks guys :D
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