Solenoids: Calculate B in Toroidal Magnetism

[m_jenny:)]

Homework Statement

A toroidal solenoid has a 60cm inner diameter and a 65cm outer diameter. The toroidal solenoid has 200 turns and carries a current of 30 Ampere. Determine the range of values for B inside the toroid.

Homework Equations

Ampere's law for toroid:
B = Uo*N*I/2*pi*r
where Uo = 4.7pi*10^-7

The Attempt at a Solution

as we are given inner diameter = 60cm and outer diameter = 65cm and since the law requires it in radius.. and as r = d/2 therefore inner radius = 30cm = 0.3m and outer radius = 32.5cm = 0.325m

and we are given N as 200 turns and Current(I) as 30 Ampere's
as we have to calculate the value inside B

subbing all given values into the Ampere's law for toroid
gives us (4PI*10^ - 7)(200)(30)/2PI(0.3) = 0.004T

I'm not sure if this is correct? can someone help me out?

thanks for the help :)

Jenny

 

[kuruman]

Looks OK, except I would use the average radius 0.3125 m.

 

[m_jenny:)]

Looks OK, except I would use the average radius 0.3125 m.

Thanks :) But is there any specific reason why you would use the average radius?

 

[kuruman]

Now that I reread the problem, I see that you are asked to find the range of values, not some kind of average which is what I was proposing. You need to calculate two values, one for the inner radius and one for the outer radius. That should give you the range of values.

 

[m_jenny:)]

ah awesome... Thank you :)