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There is a b-field observed to be rotating in the counterclockwise direction about a circular path r=3m with a tangential value of 1 tesla. the path completely encloses a solid cylinder r=2m of iron.

What is the enclosed current?

Inside the iron cylinder j= c (r*r*r)

What is B around a circular path of r=1?

Question

Help plzz! take home test!

There is a b-field observed to be rotating in the counterclockwise direction about a circular path r=3m with a tangential value of 1 tesla. the path completely encloses a solid cylinder r=2m of iron.

What is the enclosed current?

Inside the iron cylinder j= c (r*r*r)

What is B around a circular path of r=1?

anonymous · Answer

what is "j" related to the cylinder?

fretje · Answer

J is the current density?
Do you have a drawing to make this clearer?

fretje · Answer

Anyway, this equation counts for the B field:
$$\oint_\S \mathbf{B} \cdot \mathrm{d}\mathbf{A} = 0,$$
It means that all field lines that go through a closed surface, must come out again.  It's Gauss's law.