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QJEEM19Phb1d1: JEE Main 2019 Physics - Class 12 JEEM19Phb1d1 Solution: A moving coil galvanometer allows a full scale current of 10 –4 …

A moving coil galvanometer allows a full scale current of 10–4 A. A series resistance of 2 M Ω\Omega is required to convert the above galvanometer into a voltmeter of range 0-5 V. Therefore the value of shunt resistance required to convert the above galvanometer into an ammeter of range 0.10 mA is :

Multiple Choice Options

  • A 200 Ω\Omega
  • B 500 Ω\Omega
  • C 100 Ω\Omega
  • D None of the options are correct

Step-by-Step Verified Solution

Given data,

I=10−4 A,RS=2MΩ=2×106Ω,Vmax⁡=5 V\begin{aligned}I =10^{-4} \mathrm{~A}, \\\\R_S =2 \mathrm{M} \Omega=2 \times 10^6 \Omega, \\\\V_{\max } =5 \mathrm{~V}\end{aligned}

Let internal resistance of galvanometer is RGR_G .

JEE Main 2019 (Online) 10th April Morning Slot Physics - Current Electricity Question 236 English Explanation
Then,

I×RS+I×RG=Vmax⁡⇒2×106×10−4+10−4×RG=5⇒10−4RG=5−200=−195 or RG=−195×104Ω\begin{array}{lc} I \times R_S+I \times R_G=V_{\max } \\\\\Rightarrow 2 \times 10^6 \times 10^{-4}+10^{-4} \times R_G=5 \\\\\Rightarrow 10^{-4} R_G=5-200=-195 \\\\\text { or } R_G=-195 \times 10^4 \Omega\end{array}

Resistance cannot be negative.

∴\therefore No option is correct.

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