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

1. 1:4

2. 1:2

3. 2:1

4. 4:1

Doubtly Asked 30 Oct 2026 NEET UG 2025 Practice test neet Save WhatsApp Report

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Answer: 1. 1:4

Key idea: the magnetic moment of a current loop is $M=IA=I\pi r^2$.

The current is the same (2 A), so $M\propto r^2$:

$$\frac{M_1}{M_2}=\left(\frac{r_1}{r_2}\right)^2=\left(\frac12\right)^2=\frac14$$

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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