I have a coaxial cylindrical capacitor as shown, with inner radius a and outer radius b.
The potential difference across both cylinders is V. I need the magnetic field everywhere when the inner cylinder rotates with constant angular speed $\omega$. I'm kinda lost here and I don't know if what I'm doing makes sense. I used Gauss' law to find the electric field and the information about the potential difference to find $\lambda = \frac{2 \pi \epsilon_0 V}{ln(b/a)}$. Then, with Ampère's law, using the Amperian loop shown below,
$\oint \vec{B} d\vec{l} = BL = \mu_0 I$. I thought that if $s > a$, there's no current, so $B=0$. But if $s < a$, $I = \lambda \omega a L$ (because $v = \omega a$) and then $B = \frac{2 \pi \mu_0 \epsilon_0 V \omega a}{ln(b/a)}$, pointing up or down along the axis of the cylinder, depending on the direction of the angular velocity. Is this correct? If not, what should I do?