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Magnetic field of earth, how much current needed to cancel i

 
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lily25



Joined: 07 Jul 2012
Posts: 4
Location: Toronto

PostPosted: Sat Jul 07, 2012 8:48 pm    Post subject: Magnetic field of earth, how much current needed to cancel i Reply with quote

It can be shown the magnetic field in a long narrow tube that is 5 meters around which 1000 turns of wire are wrapped. its uniform and given by B(Tesla )=1.26E-6 N I(amp)?

where N is number of wire loops/meter. Assuming the solenoid is aligned along the Earth's magnetic field,how much current is needed to cancel the Earth's field?
earth's magnetic field is 10^-4 Tesla


Last edited by lily25 on Sat Jul 07, 2012 9:16 pm; edited 1 time in total
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hepcj
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Joined: 23 Jun 2007
Posts: 125

PostPosted: Sat Jul 07, 2012 9:12 pm    Post subject: Reply with quote

Are you sure this is all the information? Don't you have the number of turns in the tube?
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lily25



Joined: 07 Jul 2012
Posts: 4
Location: Toronto

PostPosted: Sat Jul 07, 2012 9:16 pm    Post subject: Reply with quote

yes sorry there are 1000 turns
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hepcj
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Joined: 23 Jun 2007
Posts: 125

PostPosted: Sun Jul 08, 2012 1:52 pm    Post subject: Reply with quote

In this case,
N per meter = 1000 turns /5 metres

N = 200 turns per metre.

B=1.26E-6 x 200 x I

and you know the Earth's B is 10^4 T
so
10^4 T = 1.26E-6 x 200 x I
Therefore, I = 10^-4/(1.26E-6 x 200) = 0.39 Amps
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hepcj
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Joined: 23 Jun 2007
Posts: 125

PostPosted: Sun Jul 08, 2012 2:13 pm    Post subject: Reply with quote

In this case,
N per meter = 1000 turns /5 metres

N = 200 turns per metre.

B=1.26E-6 x 200 x I

and you know the Earth's B is 10^4 T
so
10^4 T = 1.26E-6 x 200 x I
Therefore, I = 10^-4/(1.26E-6 x 200) = 0.39 Amps
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lily25



Joined: 07 Jul 2012
Posts: 4
Location: Toronto

PostPosted: Sun Jul 08, 2012 6:03 pm    Post subject: Reply with quote

Thanks so much i got 0.40Amps just wanted to make sure I was on the right track
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