Question

The magnetic field due to a straight conductor of uniform cross-section of radius a and carrying a steady current is represented by

• A.
• B.
• C.
• D.

Answer 1

Answer: (A)

Answer 2

The magnetic field at a point outside the straight conductor is given by $B=\frac{\mu_{0} i}{2 \pi r}$ It means $B \propto \frac{1}{r}$ (if $r>a$ ) The magnetic field at a point inside the conductor is $B=\frac{\mu_{0} i \times r}{2 \pi a^{2}}$ or $B \propto r$ (if $r < a)$