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Question: Answered & Verified by Expert
The magnetic field at the centre of a circular coil of radius $r$ carrying current $/$ is $B_1$. The field at the centre of another coil of radius $2 r$ carrying same current $/$ is $B_2$. The ratio $\frac{B_1}{B_2}$ is
PhysicsMagnetic Effects of CurrentJEE Main
Options:
  • A $\frac{1}{2}$
  • B 1
  • C 2
  • D 4
Solution:
2145 Upvotes Verified Answer
The correct answer is: 2
$B \propto \frac{1}{r} \Rightarrow \frac{B_1}{B_2}=\frac{r_2}{r_1}=\frac{2 r}{r}=2$

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