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The deflection in galvanometer falls to ...

The deflection in galvanometer falls to `((1)/(4))^(th)` when it is shunted by `3Omega`. If additional shunt of `2Omega`is connected to earlier shunt in parallel, the deflection in galvanometer falls to

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To solve the problem step-by-step, we will analyze the situation involving a galvanometer and shunt resistances. ### Step 1: Understand the Initial Condition We know that when a shunt of \(3 \, \Omega\) is connected, the deflection in the galvanometer falls to \( \frac{1}{4} \) of its original value. ### Step 2: Set Up the Equation for the First Condition Let \( I \) be the total current flowing through the circuit, \( I_g \) be the current through the galvanometer, and \( G \) be the resistance of the galvanometer. The current through the shunt \( S \) (which is \(3 \, \Omega\)) can be expressed as: \[ I_g = \frac{S}{G + S} \cdot I \] Given that the deflection falls to \( \frac{1}{4} \), we can write: \[ \frac{I_g}{I} = \frac{1}{4} \] Substituting \( S = 3 \, \Omega \): \[ \frac{1}{4} = \frac{3}{G + 3} \] ### Step 3: Solve for \( G \) Cross-multiplying gives: \[ G + 3 = 12 \implies G = 9 \, \Omega \] ### Step 4: Introduce the Additional Shunt Now, we add another shunt of \(2 \, \Omega\) in parallel with the existing \(3 \, \Omega\) shunt. We need to find the equivalent resistance \( S_{eq} \) of the two shunts in parallel: \[ \frac{1}{S_{eq}} = \frac{1}{3} + \frac{1}{2} \] Calculating the right-hand side: \[ \frac{1}{S_{eq}} = \frac{2 + 3}{6} = \frac{5}{6} \implies S_{eq} = \frac{6}{5} \, \Omega \] ### Step 5: Set Up the Equation for the New Condition Now we need to find the new deflection ratio with the equivalent shunt: \[ \frac{I_g}{I} = \frac{S_{eq}}{G + S_{eq}} \] Substituting \( S_{eq} = \frac{6}{5} \, \Omega \) and \( G = 9 \, \Omega \): \[ \frac{I_g}{I} = \frac{\frac{6}{5}}{9 + \frac{6}{5}} = \frac{\frac{6}{5}}{\frac{45}{5} + \frac{6}{5}} = \frac{\frac{6}{5}}{\frac{51}{5}} = \frac{6}{51} = \frac{2}{17} \] ### Final Answer Thus, the deflection in the galvanometer falls to: \[ \frac{2}{17} \]
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