Multimeter is used as a voltmeter when

Options

A. low resistance is connected in parallel to a galvanometer
B. high resistance is connected in parallel to a galvanometer
C. low resistance is connected in series to a galvanometer
D. high resistance is connected in series to a galvanometer

Answer

To understand how a multimeter is used as a voltmeter, we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Understanding the Components**:
- A multimeter can function as a voltmeter when it is connected to measure voltage. The main component involved is a galvanometer, which can measure current.

2. **Galvanometer Basics**:
- The galvanometer has a certain resistance (let's denote it as \( G \)) and can measure a maximum current (\( I \)). The voltage across the galvanometer can be expressed as:
\[ V = I \times G \]
- This equation shows that the voltage measured by the galvanometer depends on the maximum current and its internal resistance.

3. **Need for Higher Voltage Measurement**:
- To use the multimeter as a voltmeter, we need to measure higher voltages than what the galvanometer can handle. Since we cannot increase the maximum current (\( I \)), we need to increase the voltage range.

4. **Increasing Resistance**:
- To increase the voltage range, we can increase the effective resistance in the circuit. This can be achieved by connecting a high resistance (\( R \)) in series with the galvanometer.

5. **Connecting Resistors**:
- When we connect a high resistance in series with the galvanometer, the total voltage that can be measured becomes:
\[ V' = I \times (G + R) \]
- Here, \( R \) is the high resistance added in series. This configuration allows the multimeter to measure a larger range of voltages.

6. **Conclusion**:
- Therefore, to use a multimeter as a voltmeter, we connect a high resistance in series with the galvanometer. This configuration increases the voltage range that can be measured, making the multimeter function effectively as a voltmeter.

### Final Answer:
A multimeter is used as a voltmeter when a high resistance is connected in series with the galvanometer.

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