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

Griffiths Problem 7.8

A square loop of wire (side a) lies on a table dsiantce s from a very long straight wire, which carries a current I, as shown in teh figure.

Find the flux of B through the loop

2. Relevant equations

Flux of B is given by

[tex] \Phi_{B} = \int \vec{B} \dot d\vec{a} [/tex]

3. The attempt at a solution

THe area element is constant

but hte magnetic field is not

For a wire, B at a dsitance r is given by

[tex] \vec{B} = \frac{\mu_{0} I}{2\pi r} \hat{phi} [/tex]

Flux is then

[tex] \Phi_{B} = \int_{s}^{s+a} \frac{\mu_{0} I}{2\pi r} a^2 ds [/tex]

but hte solution says that the area element should be just a, and not a^2 .. why is that???

thanks for help!

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# Homework Help: Magnetic flux thorugh a loop of wire

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