Question

Four long,parallel conductors carry equal currents of 5.0 A. The direction of the currents is into the page at points A and B and out of the page at C and D.Calculate the magnitude and direction of the magnetic field at point P,located at the centre of the square.

Answer 1

$B_A=B_B=B_C=B_D$$=B=\frac{{\mu }_o}{2\pi }\frac{i}{r}$

$=\frac{(2\times {10}^{-7})\left(5\right)}{\left(0.2/\sqrt{2}\right)}$

$=\left(5.0\sqrt{2}\right)\times {10}^{-6}T$

Net magnetic field $=\sqrt{{(B_A+B_C)}^2+{(B_B+B_D)}^2}$
$=2\sqrt{2}B$
$=2.0\times {10}^{-5}T$ (towards bottom as shown)