Consider a circle of unit radius centered at the origin of the -plane. There exists an infinitely long current-carrying wire along the straight line:
The magnitude of the current flowing through this wire is:
Here is the permeability of free space. Compute the magnitude of the magnetic flux through the circle.
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Note: The problem is a corrected version of an earlier question. Thanks to Hosam Hajjir and Steven Chase for their inputs.
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Consider the line:
2 x − 5 = 4 y − 3 = 9 z = p
When p = 0 and p = 1 , two points passing through the line are obtained which are ( 5 , 3 , 0 ) and ( 7 , 7 , 9 ) . From here, a unit vector in the direction of the line can be obtained. That unit vector is:
L ^ = 1 0 1 2 i ^ + 4 j ^ + 9 k ^
An elementary length of the wire is:
d L = ( d p ) L ^
The position vector of any point on the line can be parameterized as:
r l = ( 1 0 1 2 p + 5 ) i ^ + ( 1 0 1 4 p + 3 ) j ^ + ( 1 0 1 9 p ) k ^
An arbitrary point on the unit circle is defined as:
r c = x i ^ + y j ^
r = r c − r l
Using Biot Savart Law:
d B = 4 π μ o I ( ∣ r ∣ 2 d L × r ^ )
The elementary area vector of the unit circle is:
d A = ( d x ) ( d y ) k ^
The magnetic flux is:
d ϕ = d B . d A
And after simplifying, we get:
ϕ = ∫ − ∞ ∞ ∫ − 1 1 ∫ − 1 − x 2 1 − x 2 ( ( 2 p − x + 5 ) 2 + ( 4 p − y + 3 ) 2 + 8 1 p 2 ) 3 / 2 1 0 1 ( 1 0 1 y − 1 0 1 2 x + 1 0 1 7 ) ( d y ) ( d x ) ( d p )
Numerically integrating the above monster gives the result of 0 . 1 4 9 4 1 5 1 8 5 7 7 T m 2