# Thread: Magnetism of a coil wire

1. If you have pass the same amount of volts through a coil with 10 turns and a coil with 100 turns do they produce the same amount of magnetic flux or does one produce more. If so is there a formula to tell the difference in the flux produced between the two.
I searched the forum and the web for several hours trying to find the answer to this question.

Thanks for the help,

2.

3. This might help:

Magnetism Information

Also, don't forget Wikipedia.

4. Originally Posted by abudantia
If you have pass the same amount of volts through a coil with 10 turns and a coil with 100 turns do they produce the same amount of magnetic flux or does one produce more. If so is there a formula to tell the difference in the flux produced between the two.
I searched the forum and the web for several hours trying to find the answer to this question.

Thanks for the help,
The wire with 100 turns will have more flux, assuming the current is the same. But if the 100 turn wire is longer (which I assume it is, since you didn't say anything about the coils being different sizes) then it will also have more resistance, so the current in the 100 turn coil will probably be a little lower than in the 10 turn coil.

5. You don't put voltage through a coil, you apply voltage across the terminals of a coil and current flows through the coil. To calculate the current flowing through the coil, you need to know its inductance. The Wikipedia article on inductance has a formula for the inductance of a circular loop. The magnetic flux is proportional to the current.

If you provide more information about what you are trying to calculate, like is it ac or dc voltage, etc., we can give you more help.

6. It is just a single piece of wire wound in a toroid shape(donut) around a core that can not be magnetized(air, plastic, whatever).

So I am trying to find a formula to determine the amount of flux that comes off of a toroid with no core. But all the formulas I found assume that the core can be magnetized and that the coil is in a straight line and is not round. Are there any formulas for this?

Also if you use 100volts and 1amp will it produce the same amount of flux as 10volts and 10amps?

Thanks for all the help,

7. I suggest you read the wikipedia article on Inductance. It tells you the relationship between inductance, current and magnetic flux. It gives you the formula for calculating the inductance of a coil given the magnetic permeability. If there is no iron core you would just use the permeability of air.

Again, the voltage doesn't make any difference in the calculation of flux, only the current does. Of course, you will get a different current if you apply a different voltage.

This is homework, isn't it?

8. Honestly its not homework at all.
I am in college but this is not my major or part of any of my classes.

I read the wikipedia articles on inductance as well as maxwell's equations but a few things didn't click with me. Under inductance of a solenoid it says.
"For rigid air-core coils, inductance is a function of coil geometry and number of turns, and is independent of current."
Wouldn't that mean that it is independent of amps?

Also, the formulas I saw all assumed that it was either just a loop or was a solenoid but if it is a toroid shape wouldn't that be different? Because with a normal (air) coil flux comes out the end and is lost but in a toroid there is no end really.

If I missed something in the article or I don't understand the concept sorry.

Thanks again for the help,

9. Okay, now I see what you are asking. The iron core of a toroid keeps most of the magnetic flux inside the toroid because the permeability is so much more than air. If you just had an air core the flux could leak out all over the place. There would be no reason for it to follow the curvature of the toroid. It would be like having a bunch of individual loops that are not aligned, not an easy thing to calculate.

The inductance of the solenoid is independent of current, but the magnetic flux is the product of the current and the inductance, so the flux is proportional to the current.

10. Got it. Thats probably why I couldn't find any formulas for calculating it.

Thanks Harold14370 for helping me understand the flux of a toroid.

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