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## Homework Statement

Hello...

I got a problem I really can't figure out.

I have the scenario in this link: http://www.gratisupload.dk/download/41677/" [Broken]

Besides that I know that there is a magnetic field that works everywhere and is along the

*z*-axis. This field, that depends on the

*y*-coordinate and the time

*t*is given as:

[tex]B=ky{{e}^{-{{t}^{2}}/{{\tau }^{2}}}}{{e}_{z}}$[/tex]

where tau is a positive time-constant,

*k*is a constant with dimension T/m and

**e**

_{z}is unit vector in the direction of the

*z*-axis.

The magnetic field raises a magnetic flux through the circuit given by:

[tex]\[{{\Phi }_{B}}={{B}_{0}}{{L}^{2}}{{e}^{-{{t}^{2}}/{{\tau }^{2}}}}\][/tex]

where

*B*

_{0}is a positive constant with dimension T.

Now determine

*k*

## Homework Equations

[tex]\[{{\Phi }_{B}}=BA\][/tex]

## The Attempt at a Solution

I know the answer is supposed to be:

[tex]\[k=2{{B}_{0}}/L\][/tex]

It seemed to good to be true if I just inserted the flux and the magnetic field into this equation, and then setting

*A*=

*L*

^{2}.

If I did that I got:

*k*=

*B*

_{0}/

*y*.

And I've been searching my book for examples and stuff I could use. But I can't come up with anything when I only have the magnetic field and magnetic flux. So I'm thinking there must be a trick that I'm not aware of :S

So can anyone point me in the right direction?

Regards.

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