CUET · PHYSICS · PYQ PAPER 2025
The dipole moment of a circular loop carrying a current I is m and the magnetic field at the centre of the loop is \( B_1 \). When the dipole moment is made three times by keeping the current I same, the magnetic field at the centre of the loop becomes \( B_2 \). The ratio of \( B_1 \) and \( B_2 \) is:
- A \( \sqrt{2} : 1 \)
- B 2 : 1
- C \( \sqrt{3} : 1 \)
- D 1 : \( \sqrt{3} \)
Answer & Solution
Correct Answer
(C) \( \sqrt{3} : 1 \)
Step-by-step Solution
Detailed explanation
\( m = I \pi r^2 \Rightarrow r = \sqrt{\frac{m}{I \pi}} \) \( B = \frac{\mu_0 I}{2r} = \frac{\mu_0 I}{2 \sqrt{\frac{m}{I \pi}}} = \frac{\mu_0 I^{3/2} \sqrt{\pi}}{2 \sqrt{m}} \) \( B \propto \frac{1}{\sqrt{m}} \) (since I is constant)…
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