Q154 / 160 · TS EAMCET 2013 · Physics

The sensitivity of a galvanometer that measures current is decreased by $\frac{1}{40}$ times by using shunt resistance of $10 \Omega$. Then, the value of the resistance of the galvanometer is

  • A
    $400 \Omega$
  • B
    $410 \Omega$
  • C
    $30 \Omega$
  • Correct answer
    D
    $390 \Omega$

Solution

$\begin{aligned} i_g & =\frac{S}{S+G} i \\ \frac{1}{40} & =\frac{10}{10+x} \\ \Rightarrow \quad 10+x & =400 \\ \Rightarrow \quad x & =390 \Omega\end{aligned}$

Hence, the correct answer is option: 'D'.

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