Magnetism Question about the MMF and a Steel Ring

[The curious]

Summary:: This question is in relation to finding the mmf of a cast steel ring. Unfortunately I do not know how to post a picture of the page showing the graph.

[Mentor Note -- Thread moved from the technical forums so no Homework Template is shown]

A cast steel ring has a cross sectional area of 600mm2 and a radius of 25mm.Determine the necessary to establish a flux of 0.8mWb in the ring. Use the B-H curve for cast steel shown on page 78. (Ans 270A)

I don't know how to post a picture of the page showing the map here. Perhaps I might be able to find it online and I will try and link it here

Thank you kindly.
Regards The Curious.

 

[berkeman]

Welcome to the PF.

I don't know how to post a picture of the page showing the map here.

You can use the "Attach files" link under the Edit window, or even just use the Windows Snipping tool to capture a screenshot of the image, and then Paste it into the Edit window.

Can you post the relevant equations for MMF and inducing flux in a metal ring? Are you going to use a current in a coil to induce this flux?

 

[The curious]

Hello burkeman
There is no coil it's a magnetic ring on it's own. I will see on how to post the details of this problem on your instructions including my workings.
Cheers
The Curious

 

[The curious]

[Mentor inserting blown-up image of the problem with better clarity]

 

[The curious]

Hello
These are the pages of both the question and the graph. I am also going to post my workings.
Cheers.

 

[The curious]

Step 1 I worked out Flux Density B=0.133T
Step 2 I found the magnetic field strength H=300. Not sure if this is good as I used a ruler on the graph in order to try and measure it to scale. (10mm = 1000At/m).
Step 3 I tried finding the magnetomotive force (mmf=Hxl).
Note. The issue is in finding the length. I assumed that I needed to find the outer circumference but I was wrong!
Any help is much appreciated
Cheers and thanks again

The Curious

 

[berkeman]

It's a bit hard to see your work (it's always best to type your work into the forum to make it clearer and to make it easier for others to quote). But did you use the centerline of the ring? It looks like that is the correct radius to use for such calculations:

http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/toroid.html

BTW, there are math symbols under the √ (square root) symbol above the Edit window, and there is a LaTeX tutorial link at the bottom of the Edit window.

 

[The curious]

Hi berkeman
Sorry about my awful handwriting. I will take your advice and use the symbols as shown. I'm just getting used to this forum. Thanks for sending me the link as I will explore it now. The image you sent of the toroid and your suggestion of using the inside part of the ring has shed some new light on this for me. Perhaps I needed the centre of the shaded area within the ring.
Cheers and thanks again.