(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!

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Magnetic flux thorugh a loop of wire

**Physics Forums | Science Articles, Homework Help, Discussion**