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Question: Answered & Verified by Expert
A coil of wire of a certain radius has 100 turns and a self inductance of $15 \mathrm{mH}$. The self inductance of a second similar coil of 500 turns will be
PhysicsElectromagnetic InductionAIIMSAIIMS 2009
Options:
  • A $75 \mathrm{mH}$
  • B $375 \mathrm{mH}$
  • C $15 \mathrm{mH}$
  • D none of these
Solution:
2462 Upvotes Verified Answer
The correct answer is: $375 \mathrm{mH}$
Inductance of a coil is given by
$\begin{aligned} & L=\frac{1}{2} \mu_0 \pi N^2 R \Rightarrow \frac{L_2}{L_1}=\frac{N_2^2}{N_1^2} \\ & \therefore L_2=L_1 \frac{N_2^2}{N_1^2}=\left(\frac{500}{100}\right)^2 15 \mathrm{mH}=375 \mathrm{mH}\end{aligned}$

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