Question

When a resistance of 5Ω is shunted with a moving coil galvanometer, it shows a full scale deflection for a current of 250 mA, however when 1050Ω resistance is connected with it in series, it gives full scale deflection for 25 volt. The resistance of galvanometer is _____Ω .

Hint:

To find the resistance of a galvanometer in series or shunted circuits, use the principles of current division and Ohm's law.

Answer 1

Correct Answer: 50

Solution:
Let \( G \) be the resistance of the galvanometer. For the shunted circuit, the total current \( I \) is given by: \[ I = 250 \, \text{mA} = 0.25 \, \text{A}. \] The current through the galvanometer is: \[ I_G = \frac{I \times S}{G + S}. \] Substituting \( S = 5 \, \Omega \) and \( I_G = 0.25 \, \text{A} \): \[ 0.25 = \frac{0.25 \times 5}{G + 5}. \] Simplifying: \[ G + 5 = 5 \quad \Rightarrow \quad G = 0 \, \Omega. \]