Hi everyone.(adsbygoogle = window.adsbygoogle || []).push({});

I need help please.

I am working on problems with solenoids and Toroids

I have solution for the solenoid:

B = μo i n

And toroid:

B = (μ o i n)/ (2Π r)

Also, I know that the magnetic field is the function of r namely: B = B(r)

r- radius of the Ampere’s path

n – number of loops per unit length

i-Current

μo – constant

My problem is:

Using the solution for the toroid, show that for the large toroid the answer can be approximated as the solenoid on the very small piece of the toroid.

I know that I have to play with limits. Something like:

a - inner radius of the toroid,

b – outer radius of the toroid,

∆a - the difference between radius a and radius b.

I think I have to take a limit when ∆a goes to 0 and in this way radius a will approach radius b. in this way the solution for the toroid SHOULD be the solution for the solenoid (on the small length L of course)

I don’t know how to set it up. How to get from the toroid solution to the solenoid solution using limits or (other technique)

Thanks for help

Chris W

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# Homework Help: Solenoids and Toroids

**Physics Forums | Science Articles, Homework Help, Discussion**