A) 20 A, perpendicular into the page
B) 40 A, perpendicular into the page
C) 20 A, perpendicular out of the page
D) 40 A, perpendicular out of the page.
Correct Answer: A
Solution :
The magnetic field due to wires LP and MQ will be zero at point O. Magnetic field at point O due to the vertical wires is given as \[B={{B}_{1}}+{{B}_{2}}=\frac{{{\mu }_{0}}}{4\pi }\frac{I}{r}(sin0+sin90)+\frac{{{\mu }_{0}}}{4\pi }\frac{I}{r}\]\[(sin0+sin{{90}^{o}})\] \[{{10}^{-4}}=2\times \frac{4\pi \times {{10}^{-7}}}{4\pi }\times \frac{I}{0.04}\Rightarrow I=20A\] By right hand thumb rule direction of magnetic field at O will be perpendicular into the page.You need to login to perform this action.
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