Question

A long staright wire carrying 5A current lies in the plane of the paper as shown in the given figure. Find the magnitude and direction of the magnetic field at point P. $[\text{Given}{\mu }_0=4\pi \times {10}^{-7}Tm/A]$

• A. $2.5\times {10}^{-7}T$
• B. $10\times {10}^{-7}T$
• C. $5\times {10}^{-7}T$
• D. $7\times {10}^{-7}T$

Answer 1

The correct option is C $5\times {10}^{-7}T$

Magnitude of the magnetic field at point P is given by:


$B=\frac{{\mu }_{0}I}{2\pi r}=\frac{4\pi \times {10}^{-7}\times 5}{2\pi \times 2}=\frac{4\pi \times 5\times {10}^{-7}}{4\pi }B=5\times {10}^{-7}T$
Direction of the magnetic field at point P can be determined by using " Right- hand thumb rule'. The magnetic field at point P will be perpendicular to the plane of the paper in upward direction.