Displacement current inside capacitor

[issacnewton]

Hi

I have already solved the problem. I just have some doubts about the solution given in the
solution manual. This is "Physics for scientists and engineers" by Serway, Jewett
In the solution for part b) , the author has taken the area of whole Amperian loop while
calculating the electric flux through it. The book itself derives the expression for the displacement current taking only the area of the capacitor plates, which makes sense , since
its probably assumed that the electric field outside the volume between the plates is zero.
So ,in the solution of the problem, the author derives the expression for the magnetic field at a distance r from the center of the capacitor plates as

$$B=\frac {\mu_{o} I r}{2A}$$

it doesn't make sense that B increases as r, distance from the center of the capacitors,
increases.

 

[issacnewton]

I think I got it, The r at which the author asks for the magnetic field is less than the radius
of the capacitor plates. So we have to consider the area of the amperian loop only.
So problem is solved.