Maxwell displacement

1. Mar 8, 2006

HI ,
I need help for this problem:

A parallel- plate capacitor is being charged at a rate of I=0.2A. The plates have an area of 0.25m2and are separeted by 1 cm.. What is the value of Integral(B*dl)for a closed path midway between the plates and covering an area of 5.0X 10-2m2?

my problem here is how to find the derivative of the flux, used in the expression of the Maxwell displacement current.

I know that the flux=E*A but then I am stuck.
Can I have some help?

Thank you
B.

2. Mar 10, 2006

lightgrav

Use Gauss to find an expression for the E-field in terms of charge Q (not sigma).
E-field is increasing due to I bringing more charge onto the plate ... I = dQ/dt.
So, Q = Q_o + I*t . Now you have a function of time, you can take d/dt of it.