Question

A galvanometer having a resistance of $180\ \Omega$ is shunted by a wire of resistance $2\ \Omega$. If the total current passing through the combination is $2\ \text{A}$, then current through shunt will be

• A. $1.8\ \text{A}$
• B. $0.9\ \text{A}$
• C. $12\ \text{A}$
• D. $12.2\ \text{A}$

Hint:

In shunt problems, current divides inversely proportional to resistance.

Answer 1

The Correct Option is A

Step 1: Use current division rule.
In parallel combination, current divides inversely proportional to resistance.
Step 2: Write current ratio.
\[ \dfrac{I_s}{I_g} = \dfrac{R_g}{R_s} \] where $R_g = 180\ \Omega$ and $R_s = 2\ \Omega$.
Step 3: Substitute values.
\[ \dfrac{I_s}{I_g} = \dfrac{180}{2} = 90 \] Step 4: Express total current.
\[ I = I_s + I_g = 2\ \text{A} \] Step 5: Calculate shunt current.
\[ I_s = \dfrac{90}{91} \times 2 \approx 1.8\ \text{A} \]