Q. A straight section $PQ\ $ of a circuit lies along the X-axis from $x = \frac{- a}{2}\ to\ x = \frac{a}{2}$ and carries a steady current $i.$ The magnetic field due to the section $PQ$ at a distance $x = + a$ will be
A) Proportional to $a$
B) Proportional to 1/ $a$
C) Proportional to $a^{2}$
D) Zero
Explanation
(d) For a point at a distance $x = + a,$ the angle between $d\ \overrightarrow{I}\ \ and\ \overrightarrow{r}$ is zero. Hence, $d\ \overrightarrow{I} \times \overrightarrow{r} = 0$.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.