# Magnetic Field in a Toroid

by sfdevil
Tags: field, magnetic, toroid
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 P: 7 1. The problem statement, all variables and given/known data Use Ampere’s law to calculate the magnetic field inside of a toroid with 850 turns. The inner radius of the rectangular coils is 3.00 cm, the outer radius is 7.00 cm. 2. Relevant equations ampere's law: path integral(B*ds) over a closed path is equal to the enclosed current times mu_0 3. The attempt at a solution by ampere's law for toroids, I get B= mu_0*N*I/(2*pi*R) Im confused as to what the inner and outer radius have to do with this problem, hence the cry for help :( anyone ?
 Emeritus Sci Advisor PF Gold P: 4,980 The two radii are there so you can determine the axis of toroidal coils. This is chosen as it simplifies Amperes circuital law to the equation you have stated.
 P: 7 so basically these numbers dont really matter, right ? since Im finding the magnetic field inside the toroid, its just gonna be r as an arbitrary length from the center to some point inside (between 3 and 7 cms) ....correct ? if so, then the final solution is mu_0*850*I/(2*pi*R), right ?
 Emeritus Sci Advisor PF Gold P: 4,980 Magnetic Field in a Toroid If you have a look at the following page it may become clearer. http://hyperphysics.phy-astr.gsu.edu...ic/toroid.html
 P: 7 so from that explanation, I got that since inner radius is 3 and outer is 7, then radius of the rectangular cross-section is 4/2=2 so r=3+2=5 thats about as much as I could get from that page, please let me know If Im still missing something...
 Emeritus Sci Advisor PF Gold P: 4,980 That should be ok.

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