CUET · PHYSICS · PYQ PAPER 2025
A cylindrical, straight long wire having radius 'a' is carrying current 'I' uniformly distributed inside the wire. As per Ampere's circuital law, the magnetic field inside the wire at any distance r, (r < a) is given by:
- A \( B = \mu_0 I / 2\pi r \)
- B \( B = \mu_0 I a / 2\pi r \)
- C \( B = \mu_0 I r / 2\pi a^2 \)
- D \( B = \mu_0 I a / 2\pi r^2 \)
Answer & Solution
Correct Answer
(C) \( B = \mu_0 I r / 2\pi a^2 \)
Step-by-step Solution
Detailed explanation
\(I_{enc} = I \frac{r^2}{a^2}\) \(B \cdot 2\pi r = \mu_0 I_{enc}\) \(B = \frac{\mu_0 (I r^2 / a^2)}{2\pi r} = \frac{\mu_0 I r}{2\pi a^2}\)
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