CUET · PHYSICS · PYQ PAPER 2025
A thick long straight wire of radius 'a' is carrying steady current I. The current I is uniformly distributed across the cross-section. The ratio of magnetic fields at a distance a/2 and 3a/2 from the central axis of the wire is
- A \(2: 3\)
- B \(3: 2\)
- C \(3: 4\)
- D \(4: 3\)
Answer & Solution
Correct Answer
(C) \(3: 4\)
Step-by-step Solution
Detailed explanation
\(B_{in} = \frac{\mu_0 I r}{2 \pi a^2}\), \(B_{out} = \frac{\mu_0 I}{2 \pi r}\) \(B_{1} = B(a/2) = \frac{\mu_0 I (a/2)}{2 \pi a^2} = \frac{\mu_0 I}{4 \pi a}\) \(B_{2} = B(3a/2) = \frac{\mu_0 I}{2 \pi (3a/2)} = \frac{\mu_0 I}{3 \pi a}\)…
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