## PHYS208 Fundamentals of Physics II

### Hint for Ch. 31, 29P

a) B is not uniform over the area enclosed by the conducting loop; you must decide how
to set up the integral to evaluate the flux. B depends only on how far away *z*
the point of consideration is from the long straight wire; thus spanning the rectangular loop
with rectangular "slivers" of *dA* = *a* *dz* is a good way to proceed.

b) Now that the flux is evaluated, find the time derivative. Keep in mind that *r* is
time dependent so use the chain rule for differentiation and replace *dr*/*dt*
with *v* when it appears.

Thanks to Femi Ogunsola for suggesting that I switch to *z* as a dummy
variable of integration rather than using *r* which was specified to be the
distance of the center of the loop from the wire.

"http://www.physics.udel.edu/~watson/phys208/exercises/hints/31-29P.html"

Last updated Nov. 11, 1997.

Copyright George Watson, Univ. of Delaware, 1997.