The resistance of a moving coil galvanometer is `20Omega`. It requires 0.01A current for full scale deflection calculate the value of resistan ce required to convert it into a voltmeter of range 20 volt.

Answer

To convert a moving coil galvanometer into a voltmeter, we need to add a high resistance in series with the galvanometer. The total voltage across the voltmeter will be the sum of the voltage across the galvanometer and the voltage across the added resistance.

### Step-by-Step Solution:

1. **Identify Given Values**:
- Resistance of galvanometer, \( R_g = 20 \, \Omega \)
- Full-scale deflection current, \( I_g = 0.01 \, A \)
- Desired voltage range of the voltmeter, \( V = 20 \, V \)

2. **Calculate the Voltage across the Galvanometer at Full Scale**:
\[ V_g = I_g \times R_g \]
Substituting the values:
\[ V_g = 0.01 \, A \times 20 \, \Omega = 0.2 \, V \]

3. **Determine the Total Resistance Needed for the Voltmeter**:
The total voltage across the voltmeter is given by:
\[ V = I_g \times (R_g + R) \]
where \( R \) is the resistance to be added. Rearranging gives:
\[ R + R_g = \frac{V}{I_g} \]
Substituting the known values:
\[ R + 20 \, \Omega = \frac{20 \, V}{0.01 \, A} = 2000 \, \Omega \]

4. **Calculate the Required Resistance \( R \)**:
\[ R = 2000 \, \Omega - 20 \, \Omega = 1980 \, \Omega \]

### Final Answer:
The resistance required to convert the galvanometer into a voltmeter of range 20 volts is \( R = 1980 \, \Omega \).