A gavanometer shows full-scale deflection for a current of 1mA. Resistance of the coil of the galvanometer is `100Omega`. What shunt is required to convert it into an ammeter which can measure a current of 1A?

Options

A. `0.01 Omega`
B. `0.1 Omega`
C. `0.001 Omega`
D. `1 Omega`

Explanation

To solve the problem of finding the shunt resistance required to convert a galvanometer into an ammeter, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Given Values**:
- Full-scale deflection current of the galvanometer, \( I_G = 1 \, \text{mA} = 1 \times 10^{-3} \, \text{A} \)
- Resistance of the galvanometer coil, \( R_G = 100 \, \Omega \)
- Desired maximum current to measure, \( I = 1 \, \text{A} \)

2. **Determine the Current through the Shunt**:
- The current \( I \) flowing through the circuit is the sum of the current through the galvanometer and the current through the shunt:
\[ I = I_G + I_S \]
- Rearranging gives:
\[ I_S = I - I_G = 1 \, \text{A} - 1 \times 10^{-3} \, \text{A} = 0.999 \, \text{A} \]

3. **Use the Formula for Shunt Resistance**:
- The relationship between the currents and resistances can be expressed as:
\[ I_G \cdot R_G = I_S \cdot R_S \]
- Substituting the known values:
\[ (1 \times 10^{-3}) \cdot 100 = (0.999) \cdot R_S \]

4. **Solve for the Shunt Resistance \( R_S \)**:
- Calculate the left side:
\[ 0.1 = 0.999 \cdot R_S \]
- Rearranging gives:
\[ R_S = \frac{0.1}{0.999} \approx 0.1001 \, \Omega \]

5. **Final Result**:
- The shunt resistance required is approximately:
\[ R_S \approx 0.1 \, \Omega \]

### Summary:
To convert the galvanometer into an ammeter that can measure up to 1 A, a shunt resistance of approximately \( 0.1 \, \Omega \) is required.