Q51 / 75 · JEE Main 2025 (23 Jan Shift 2) · Physics

A galvanometer having a coil of resistance $30 \Omega$ need 20 mA of current for full-scale deflection. If a maximum current of 3 A is to be measured using this galvanometer, the resistance of the shunt to be added to the galvanometer should be $\frac{30}{X} \Omega$, where $X$ is Options

  • A
    596
  • Correct answer
    B
    149
  • C
    298
  • D
    447

Solution

$\begin{aligned} & \left(I-I_g\right) R=I_g G \\ & (3-0.02) \times R=0.02 \times G \Rightarrow R=\frac{30}{149} \\ & \Rightarrow 149=\text { Required } X\end{aligned}$

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

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