# Homework Help: Solenoids (Magnetism)

1. Sep 7, 2009

### m_jenny:)

1. The problem statement, all variables and given/known data

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.

2. Relevant equations

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

3. 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

Last edited: Sep 7, 2009
2. Sep 7, 2009

### kuruman

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

3. Sep 7, 2009

### m_jenny:)

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

4. Sep 7, 2009

### 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.

5. Sep 7, 2009

### m_jenny:)

ah awesome... Thank you :)