Which of the following statements is correct during measurement of emf of cell by potentiometer ? .

Options

A. No current flows through potentiometer wire upto position of null point
B. At null point in any potentiometer experiment no current flows through whole of potentiometer wire .
C. No current is drawn from cell when null point is obtained
D. No current is drawn from battery when null point is obtained

Answer

To determine which statement is correct during the measurement of the EMF of a cell by a potentiometer, we can analyze each statement based on the principles of how a potentiometer operates.

### Step-by-Step Solution:

1. **Understanding the Potentiometer Setup:**
- A potentiometer consists of a long wire (let's denote it as AB) connected to a known voltage source (battery).
- The unknown EMF (E) of the cell is connected in series with a galvanometer and a jockey (a sliding contact).

2. **Balancing Point:**
- When the jockey is moved along the potentiometer wire, a point is reached (let's call it C) where the potential difference across the segment AC of the wire is equal to the EMF of the cell (E).
- At this point, the galvanometer shows zero current, indicating that the potential difference across the wire matches the EMF of the cell.

3. **Analyzing the Statements:**
- **Statement A:** "No current flows through the potentiometer wire up to the position of null point."
- This statement is **incorrect**. Current flows until the jockey reaches the null point, where the potential difference across AC equals the EMF.

- **Statement B:** "At null point in any potentiometer experiment, no current flows through the whole of the potentiometer wire."
- This statement is also **incorrect**. While there is no current through the galvanometer at the null point, the battery maintains a current through the potentiometer wire.

- **Statement C:** "No current is drawn from the cell when the null point is obtained."
- This statement is **correct**. At the null point, the potential difference across AC equals the EMF of the cell, resulting in zero current drawn from the cell.

- **Statement D:** "No current is drawn from the battery when the null point is obtained."
- This statement is **incorrect**. The battery continues to supply current to maintain the potential difference across the potentiometer wire.

4. **Conclusion:**
- The correct statement during the measurement of EMF of a cell by a potentiometer is **Statement C**: "No current is drawn from the cell when the null point is obtained."