The Magnetic Field in a Charging Capacitor problem

[cupcake]

A parallel-plate capacitor of capacitance C with circular plates is charged by a constant current I. The radius a of the plates is much larger than the distance d between them, so fringing effects are negligible. Calculate B(r), the magnitude of the magnetic field inside the capacitor as a function of distance from the axis joining the center points of the circular plates.

Express your answer in terms of mu_0 and given quantities.

according to Ampère's law as extended by Maxwell:
$$<br /> \oint \vec{B} \cdot d\vec{l}= \mu_0\left(I+ \epsilon_0 \frac{d\Phi}{dt}\right).<br />$$


what should i do then?
please advise...

 

[cupcake]

anyone can help me?

 

[nealh149]

Pick an amperian surface, and calculate either current or electric flux through that surface. That will give you the value of the right side of the equation. Then solve for B.

 

[cupcake]

Pick an amperian surface, and calculate either current or electric flux through that surface. That will give you the value of the right side of the equation. Then solve for B.

how to calculate flux through the that surface??