Q. The direction of induced magnetic field dB due to current element $i$ dL, at a point of distance $r$ from it, when a current $i$ passes through a long conductor is in the direction
A) Of position vector r of the point
B) Of current element dL
C) Perpendicular to both dL and r
D) Perpendicular to dL only
Explanation
(c) Biot-Savart law states
$\mathbf{dB} = \frac{\mu_{0}}{4\pi}\frac{i\mathbf{dL \times r}}{r^{3}}$
$\therefore\ $ Direction of dB is perpendicular to both dL and r.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.