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JEE Mains · Physics · STD 12 - 4. Moving charges and magnetism

When a resistance of \(5\,\Omega\) is shunted with a moving coil galvanometer, it shows a full scale deflection for a current of \(250\,mA\), however when \(1050\,\Omega\) resistance is connected with it in series, it gives full scale deflection for \(25\) volt. The resistance of galvanometer is \(......\,\Omega\).

  1. A \(40\)
  2. B \(30\)
  3. C \(50\)
  4. D \(20\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(50\)

Step-by-step Solution

Detailed explanation

\(\frac{250\,mA \times 5}{5+R_G}=i \dots(i)\) \(i=\frac{25}{1050+R_G} \dots(ii)\) From \((i)\) and \((ii)\) \(\frac{25}{1050+R_G}=\frac{5}{4\left(5+R_G\right)}\) \(100\left(5+R_G\right)=1050 \times 5+R_G \times 5\) \(95 R_G=4750\) \(R_G=50\,\Omega\)
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