(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

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 thez-axis. This field, that depends on they-coordinate and the timetis given as:

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

where tau is a positive time-constant,kis a constant with dimension T/m ande_{z}is unit vector in the direction of thez-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]

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

Now determinek

2. Relevant equations

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

3. 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 settingA=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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# Homework Help: Find k from magnetic field and magnetic flux.

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