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Physics · Moving Charges and Magnetic Field

NEET (UG) 2025 — Question 11

A 2 amp current is flowing through two different small circular copper coils having radii ratio 1:21: 2. The ratio of their respective magnetic moments will be

  1. Option A:

    1:41: 4

    Correct
  2. Option B:

    1:21: 2

  3. Option C:

    2:12: 1

  4. Option D:

    4:14: 1

Answer: A

Step-by-step solution

Magnetic moment M=I(A)\mathrm{M}=\mathrm{I}(\mathrm{A})

M=I(πr2)\mathrm{M}=\mathrm{I}\left(\pi \mathrm{r}^{2}\right)

M1M2=Iπr12Iπr22=(r1r2)2=(12)2\frac{\mathrm{M}_{1}}{\mathrm{M}_{2}}=\frac{\mathrm{I} \pi \mathrm{r}_{1}^{2}}{\mathrm{I} \pi \mathrm{r}_{2}^{2}}=\left(\frac{\mathrm{r}_{1}}{\mathrm{r}_{2}}\right)^{2}=\left(\frac{1}{2}\right)^{2}

M1M2=14\frac{\mathrm{M}_{1}}{\mathrm{M}_{2}}=\frac{1}{4}

Answer key and solution verified before publishing.

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Exam
NEET (UG) 2025
Paper
2025 paper
Subject
Physics
Chapter
Moving Charges and Magnetic Field
Topic
Force and Torque on Wires and Loops, Magnetic Dipole Moment

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