# Calculating Tesla's / Gauss

1. Jan 8, 2011

### mvan4310

Hello,

Im wondering how I would go about getting the amount of tesla's or gauss from an electromagnet without using a gauss-meter.

Thank you in advance,
Michael

2. Jan 8, 2011

3. Jan 8, 2011

### Bob S

Hi Michael-
Are you talking about an air-core electromagnet, or an iron-dominated one? Is this a dc electromagnet, or an ac (or pulsed) one? Is there a particular place in the electromagnet where you want to know the magnetic field? Is this a real magnet, or a paper design?What is the purpose of the magnet?

Bob S

4. Jan 8, 2011

### mvan4310

Would be a DC Air-Core electromagnet. There is no particular place, but having the option to find the strength from any point would be a plus. It would be a real electromagnet. And the purpose is studying electromagnets.

EDIT: Also, I know the strength relies on the permeability of the core, so, is there a list with permeabilities of different materials, both plastic and metal? Also, I know Im getting complicated, but lets say I dont know the materials Im using, how would we get the permeability?

Thank you,
Michael

Last edited: Jan 8, 2011
5. Jan 8, 2011

### Bob S

The magnetic field calculation in post #2 is incorrect for a finite length, finite diameter solenoid coil. Use

http://www.netdenizen.com/emagnettest/solenoids/?solenoid

The simplest way of measuring the magnetic field is a Hall Effect probe, such as the linear ones from Allegro Micro like the A321. See

http://www.allegromicro.com/en/Products/Part_Numbers/1321/index.asp

http://www.allegromicro.com/en/Products/Part_Numbers/1321/1321.pdf

Get the SIP package. You might be able to get a free sample.

Bob S

6. Jan 8, 2011

### mvan4310

Ok, now would it possible for you to explain this newbie style. Im looking at it a little confused, but can grasp a basis of it. Now if you can run me through actually using it, I would greatly appreciate it.

Thank you,
Michael

7. Jan 9, 2011

8. Jan 9, 2011

### Bob S

Here is an off-axis field-strength formula and calculator for a simple finite-size solenoid. See

http://www.vizimag.com/calculator.htm

It requires evaluating complete elliptic integrals of the first and second kind. There may be a Mathematica application that does this calculation.

Bob S

9. Jan 9, 2011

### mvan4310

10. Jan 9, 2011

### Bob S

Note that there are no coil dimensions in it. You can use this for a very small single-turn coil field distribution.

Bob S

11. Jan 9, 2011

### mvan4310

Ok, I know Mathematica will do the calculations easy, And Wolfram provides and online resource for calculating this, but a quick question, can you explain them a little for me, as far as the inputs in the current context of this thread?

12. Jan 10, 2011

### Bob S

Are you interested in the magnetic field in the gap of a "C" magnet, like in the thumbnail?

Bob S

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13. Jan 10, 2011

### mvan4310

Now that you ask, I was actually looking into that as well. I was going to end up asking later about other types of electromagnets as well. Because all of the equations I have found have dealt with Solenoids, but now am looking into other types of electromagnets so i dont end up asking this question later on. Do you happen to have equations for various types like the one you have provided?

Thanks,
Michael

14. Jan 10, 2011

### mvan4310

Or if you can give me a resource that I can look all this information up in, that would be a great help as well. Im looking around the web, but havnt found much but straight solenoids. If you can provide a solution for a whole variety or a resource to help me out instead of bugging you, I would greatly appreciate it.

Thanks,
Michael

15. Jan 10, 2011

### mvan4310

Ok, Another post. Sorry about all of the posting. After looking around a little bit more, I have found some more on the subject, some in a few physics books and other resources. So what I have found is a formula for a solenoid of a specific length, certain number of turns, and such. But out of all of the different solutions, I havnt found any that would include a certain number of layers of turns. So lets say we have a solenoid, we have the equations to figure it out if it was straight with a single layer of N turns. What about x amount of layers of N turns?

And lets say the solenoid isnt straight, and it is curved, in various shapes, would that be evaluated the same way as a straight one if we are looking at the center of the core? Lots of questions, so if you can point me to an advanced book that explains this to me instead of having to type everything down, that will be fine. Im just looking to get a good understanding of the whole process and how each is figured out.

Thanks again,
Michael

16. Jan 11, 2011

### Bob S

This formula gives the correct on-axis field for a finite-lengh multilayer air-core solenoid:

http://www.netdenizen.com/emagnettest/solenoids/?solenoid

The thumbnail in post # shows a straight multilayer solenoid, with an iron core. Some physics E & M books provide simple magnet designs. Also look at pages 100-101 in Humphries' free online downloadable book on principles of charged particle acceleration:

http://www.fieldp.com/cpa.html

Bob S

17. Jan 11, 2011

### mvan4310

Ok, the link for the solenoid, if I wished to use a different type of core, say an iron core or later on some type of superconducting materials, what modifications to the equation would need to be made? I imagine superconducting materials require a bit more then say an iron core, but just curious how to account for different cores and coil materials.

Thanks,
Michael

Last edited: Jan 11, 2011
18. Jan 12, 2011

### Bob S

The magnetic field of a superconducting coil will saturate any iron core. You can easily get B = μ0NI = 3 Tesla in the superconducting coil, but the iron saturates at 1.5 Tesla.

Bob S