JEE PYQ: Magnetic Effects Of Current Question 39
Question 39 - 2019 (10 Apr 2019 Shift 2)
A square loop is carrying a steady current $I$ and the magnitude of its magnetic dipole moment is $m$. If this square loop is changed to a circular loop and it carries the same current, the magnitude of the magnetic dipole moment of circular loop will be:
(1) $\frac{m}{\pi}$
(2) $\frac{3m}{\pi}$
(3) $\frac{2m}{\pi}$
(4) $\frac{4m}{\pi}$
Show Answer
Answer: (4) $\frac{4m}{\pi}$
Solution
Same perimeter: $2\pi r = 4a$, $r = \frac{2a}{\pi}$. $M_1 = I\pi \times \frac{4a^2}{\pi^2} = \frac{4Ia^2}{\pi} = \frac{4m}{\pi}$.
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