Mag field strength

[chiddler]

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Book says force due to magnetic field drops in a square relationship with distance.

I'm trying to find the formula that describes this!

So far: Ampere's law (algebra-fied) is B = uo*I/2pi*r around a wire

and throw that into F = qvB

to make it a linear relationship...

help :<

 

[milski]

Magnetic field created by what? That would matter.

 

[chiddler]

Magnetic field created by what? That would matter.

magnets. which would make what i wrote incorrect as that only applies to current in wires!

 

[milski]

magnets. which would make what i wrote incorrect as that only applies to current in wires!

As in permanent magnets? That's generally out of the scope of intro physics and is non-trivial. What exactly does the book say?

 

[chiddler]

As in permanent magnets? That's generally out of the scope of intro physics and is non-trivial. What exactly does the book say?

This is a true choice in a question:

"The strength of attraction and repulsion of electric charges or magnetic poles vary inversely as the square of the distance between the charges or poles."

 

[milski]

This is a true choice in a question:

"The strength of attraction and repulsion of electric charges or magnetic poles vary inversely as the square of the distance between the charges or poles."

It's obviously true for electric charges. I'd mark the magnetic part of the question as dubious estimation and consider the other answers. If there's something only about electrical charges, I'd pick that. Anything else being worse, that's a plausible albeit non-ideal answer.

 

[chiddler]

It's obviously true for electric charges. I'd mark the magnetic part of the question as dubious estimation and consider the other answers. If there's something only about electrical charges, I'd pick that. Anything else being worse, that's a plausible albeit non-ideal answer.

yup! the difficulty wasn't picking correct answer, anyway. i just thought that this is something i should know and do not.

thanks very much for your help.