physics
posted by may .
An infinitely long thin metal strip of width w=12cm carries a current of I=10A that is uniformly distributed across its cross section. What is the magnetic field at point P a distance a=3cm above the center of the strip as shown? This one requires some integration! I suggest you solve it symbolically first, then plug in numbers.

I agree with the hint!
What is the question here?
Here is an MIT solution..
http://ocw.mit.edu/courses/physics/802electricityandmagnetismspring2002/assignments/pss5.pdf
see prob 5.3