A long, straight wire carries a current of 1.7 A in the +z direction and lies along the line x = –3.0 cm, y = 0. A second such wire carries a current of 1.7 A in the +z direction and lies along the line x = +3.0 cm, y = 0, as shown in Figure. Find the magnetic field at a point P on the y axis at y = 6.0 cm.
The Attempt at a Solution
I understood why BL = BR
In my textbook, the solution says that vector B is the vector sum of vector BL and vector BR.
I don't understand this:
It says vector B = -2BL cos (theta) i ( in the -x direction)
i is the unit vector here
I have no idea where does the -2BL cos (theta) come from!
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