Q129 / 180 · JIPMER 2016 · Physics

A galvanometer of resistance $25 \Omega$ shows a deflection of 5 divisions when a current of 2 mA is passed through it. If a shunt of $4 \Omega$ is connected and there are 20 divisions on the scale, then the range of the galvanometer is

  • A
    1 A
  • B
    58 A
  • Correct answer
    C
    58 mA
  • D
    30 mA

Solution

There are 20 divisions on scale. Initially, current for 20 divisions $=\frac{2 \times 20}{5}=8 \mathrm{~mA}$ $\begin{array}{ll}\therefore & I g=8 \mathrm{~mA} \\ \because & \frac{I g}{I}=\frac{S}{S+G}\end{array}$ $\begin{aligned} \Rightarrow \quad I & =\left(\frac{S+G}{S}\right) I_g \Rightarrow I=\left(\frac{4+25}{4}\right) \times 8 \\ & =29 \times 2=58 \mathrm{~mA}\end{aligned}$

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

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