Section 1: An infinite streamline in air lies along the z-axis, the direction of the current of magnitude I is in +az. 3

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Section 1:
An infinite streamline in air lies along the z-axis, the direction
of the current of magnitude I is in +az.
3.1 (5%) Determine the energy density due to the magnetic field at
a distance “r” from the line.
Section 2:
In the air there are three infinite filamentary lines with electric
current, all parallel to each other and all parallel to the z
axis.
i) The first line L1 passes through y = - d, being parallel to
the z axis, this line carries a current of magnitude I in address -
az.
ii) The second line L2 passes through y = 0, being parallel to the
z axis, this line carries a current of magnitude I in direction +
z.
iii) The third line L3 passes through y = +d, being parallel to the
z axis, this line carries a current of magnitude I in address -
az.
It is fulfilled: – d < 0 < d.
With the information make a clear diagram of the problem.
3.2 (14%) Determine the force per unit length (l) exerted by Line 1
on Line 3, that is FL1→L3/l.
3.3 (14%) Determine the force per unit length (l) exerted by Line 2
on Line 3, that is FL2→L3/l