CUET · PHYSICS · PYQ PAPER 2023
A steady current I flow through a long straight wire of radius 'a'. The current is uniformly distributed across its cross section. The ratio of the magnetic fields due to the wire at distance a/4 and 3a respectively from the axis of the wire is
- A \( 3:4\)
- B \( 4:3\)
- C \( 2:3\)
- D \( 1:4\)
Answer & Solution
Correct Answer
(A) \( 3:4\)
Step-by-step Solution
Detailed explanation
\( B_{in} = \frac{\mu_0 I r}{2\pi a^2} \) \( B_{out} = \frac{\mu_0 I}{2\pi r} \) \( B_{a/4} = \frac{\mu_0 I (a/4)}{2\pi a^2} = \frac{\mu_0 I}{8\pi a} \) \( B_{3a} = \frac{\mu_0 I}{2\pi (3a)} = \frac{\mu_0 I}{6\pi a} \)…
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