Physics
posted by Valerie .
A singleturn square loop of side L is centered on the axis of a long solenoid. In addition, the plane of the square loop is perpendicular to the axis of the solenoid. The solenoid has 1490 turns per meter and a diameter of 6.00 cm, and carries a current of 2.46 A. Find the magnetic flux through the loop in each of the following.
a) L = 3cm
b) L = 6cm
c) L = 12cm
I found a to be 4.15e6, b to be 1.66e5 and c to be 6.63e5, but only a is right. the answers are within ten percent of 1.2e5 and are the same answer but I can't find what they should be. Please someone help soon.

Hmmm. A is right, you say.
The area of L^2 in a is 9cm^2
the area of the solenoid is 9PI
Area outside the solenoid does not contain the inner field.
b. Flux=4.15E6* 9PI/9=4.15E6*PI=1.304E5
That is 8 percent higher than 1.2E5
Now, larger L does not contain any more flux, as the flux is contained within the solnoid
Think about this, I may not be understanding the problem.