Two long, straight wires cross each other at right angles, as shown in the figur

Question

Two long, straight wires cross each other at right angles, as shown in the figure below.

(a) Find the direction and magnitude of the magnetic field at point P, which is in the same plane as the two wires.

(b) Find the magnetic field at a point 31.5 cm above the point of intersection (31.5 cm out of the page, toward you).

choices of directions are; into the page, out of the page, 31 clockwise to x-direction, 5

Magnitude 1
Your response differs from the correct answer by more than 100%. T Direction 2 ---Select--- 31.0° clockwise from the +x direction 59.0° counterclockwise from the +x direction 59.0° clockwise from the +x direction 59.0° counterclockwise from the -x direction into the page out of the page

Explanation / Answer

a)

Since they are infinitely long wires, B=oi/2r

for the 5A wire, mag field is out of the page.

for 3A wire, mag field is into the page.

So total B=o/2*(5/0.4 - 3/0.3)

=o/2 (2.5)

=5x10-7 T out of the page

 

for b)

B because of 3A is towards +ve x axis,

B because of 5A is towards -ve y axis.

Therefore, net mag field is x2+y2 (where x and y are mag fields for respective wires)

=o/(2*0.315)25+9

=3.7x10-6 T

for direction, it's tan inverse of y/x

so tan inverse of (5/3)

=59 degrees, clockwise from +ve x

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