Q.
Net magnetic field at the centre of the circle O due to a current through a loop as shown in figure ($\theta < 180{^\circ})$
A) zero
B) Perpendicular to paper inwards
C) Perpendicular to paper outwards
D) Perpendicular to paper inwards if $\theta\ \leq 90{^\circ}$ and perpendicular to paper outwards if $90{^\circ}\ \leq \ \theta < 180{^\circ}$
Explanation
(b) The current through loop is anticlockwise. Hence, magnetic field at the points within the loop is perpendicular to paper outwards. As the magnetic lines of force form a closed path and tangent to line of force tells the direction of magnetic field at that point. Hence, magnetic field at $O$ is perpendicular to paper inwards.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.