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Magnetic Effect of Current — JEE physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 ScienceJEE physicsMagnetic Effect of Current1 Mark
MCQ
A galvanometer gives full scale deflection with $0.006$ A current. By connecting it to a $4990 \ \Omega$ resistance, it can be converted into a voltmeter of range $0-30 \ V$. If connected to a $\frac{2 n }{249} \Omega$ resistance, it becomes an ammeter of range $0-1.5 \ A$. The value of $n$ is:
  • A
    $2$
  • B
    $3$
  • C
    $4$
  • D
    $5$
✓

Answer

$\frac{6}{1000}(G+4990)=30 $

$\Rightarrow G+4990=\frac{30,000}{6}=5000 $

$\Rightarrow G=10 $

$\frac{6}{1000} \times 10=\left(1.5-\frac{6}{1000}\right) S $

$\Rightarrow S =\frac{60}{1494}=\frac{2 n}{249} $

$\Rightarrow=\frac{249 \times 30}{1494}=\frac{2490}{498}=5$

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