# Value of line integral

1. Dec 14, 2008

### lovinuz

1. The problem statement, all variables and given/known data
There is a constant electric field E = E0sin(kz+wt+pi/3) k(direction vector). What is the value of the line integral(P) B.dl, where P is a circular path, centered on the origin, lying in the xy-plane, having radius r?

2. Relevant equations
integral E.dl = -dI/dt

3. The attempt at a solution
I am having difficulty approaching this question, can someone please give me some kind of push? Thanks.

2. Dec 14, 2008

### James R

First, that isn't a constant electric field. It varies with time.

Second, your equation in (2) should read:

$$\int B.dl = +\epsilon_0 \mu_0 \frac{d\Phi_E}{dt}$$

so that the line integral of the magnetic field B around the circle relates to the change in electric flux passing through the loop.

The equation you quoted looked like it was for the line integral of the electric field around a closed loop.

Can you see where to go from here?

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