#### transgalactic

##### Banned

http://i25.tinypic.com/fc8rqr.jpg

there is endless cylinder i which we only see its crossection in the photo.

its radius is [latex]R_1[/latex] a distance d from the center a cylinder with radius [latex]R_2[/latex]

along the cylinder flows current I in a uniform way inside the page(X).

1.what is the magnetic field in x>0 region?

2.what is the magnetic field in (0,[latex]R_1[/latex])?

i tried to solve it by amperes law

[latex]\oint \vec{B}\vec{dl}=\mu_0 I[/latex]

0<r<d

[latex]\oint \vec{B}\vec{dl}=\mu_0 I\\[/latex]

[latex]I_0=I\frac{\pi r^2}{\pi R_1^2}=I\frac{ r^2}{R_1^2}\\[/latex]

[latex] B =\mu_0 I\frac{ r^2}{R_1^2 2\pi r}\\[/latex]

have i done the first region correctly