PhysicsNEET 2019Biot–Savart and Ampère's laws

Moving Charges and Magnetism

A cylindrical conductor of radius $R$ carries a constant current, uniformly distributed over its cross-section. Which of the following best describes the magnitude of the magnetic field $B$ as a function of the distance $d$ from the axis of the conductor?

A. $B$ rises to a peak before $d = R$ , then drops sharply to zero at $d = R$ and stays zero for $d > R$
B. $B$ is zero for $d < R$ , then jumps up sharply at $d = R$ and stays at that high value for $d > R$
C. $B$ increases linearly with $d$ for $d < R$ , reaches its maximum at $d = R$ , and decreases (as $1/ d$ ) for $d > R$ ✓
D. $B$ is zero for $d < R$ , then rises and levels off to a constant value for $d > R$

You have the answer. The worked solution — and why the other three were written — is part of a paid pack.

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