The potentiometer is best for measuring voltage as .

Options

A. It has a sensitive galvnometer
B. It has wire of higher resistance
C. It measures p.d in closed circuit
D. It measures p.d in open circuit

Answer

To solve the question regarding why a potentiometer is best for measuring voltage, we can break it down into clear steps:

### Step-by-Step Solution:

1. **Understanding the Potentiometer Setup**:
- A potentiometer consists of a long wire of uniform resistance connected across two terminals (A and B). The total resistance of the wire is denoted as R, and its length is denoted as S.

2. **Connecting the Battery**:
- To measure the electromotive force (EMF) of an external battery, connect the positive terminal of the battery to terminal A of the potentiometer and the negative terminal to a galvanometer, which is then connected to a jockey.

3. **Finding the Null Deflection Point**:
- Move the jockey along the potentiometer wire until you find a point (C) where the galvanometer shows zero deflection. This point indicates that there is no current flowing through the galvanometer.

4. **Understanding Null Deflection**:
- The null deflection point means that the current (I) in the circuit is zero. This indicates that the circuit is effectively an open circuit at this point.

5. **Implications of Open Circuit**:
- Since the current is zero, there is no potential drop across the potentiometer wire (R). Therefore, the potential difference between points A and C is equal to the EMF of the battery being measured.

6. **Conclusion**:
- The potentiometer is the best instrument for measuring voltage because it measures potential difference in an open circuit condition, allowing for accurate measurement without any current flowing through the circuit.

### Final Answer:
The potentiometer is best for measuring voltage because it measures potential difference in an open circuit.

---