Discussion Forum



1)

 A galvanometer gives full-scale deflection with 0.006 A current. By connecting it to a 4990Ω resistance, it can be converted into a voltmeter of range 0-30V. If connected to a  $\frac{2n}{249}$ Ω resistance, it becomes an ammeter of range 0-1.5 A. The value of n is 


A) 3

B) 4

C) 5

D) 6

Answer:

Option C

Explanation:

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$i_{g}(G+4990)=V$

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

$\Rightarrow$    $G+4990=\frac{30000}{6}=5000$

$\Rightarrow$             G=10Ω

                       Vab  =Vcd

$\Rightarrow$               $i_{g}G=(1.5-i_{g})S$

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 $\Rightarrow$      $ \frac{6}{1000}\times10 = \left( 1.5-\frac{6}{1000}\right)S$

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

$\Rightarrow$      $ n=\frac{249\times30}{1494}=\frac{2490}{498}=5$