In a potentiometer arrangement for determining the emf of cell, the balance point of the cell in open circuit is 350 cm. When a resistance of `9 Omega` is used in the external circuit of cell , the balance point shifts to 300 cm. Determine the internal resistance of the cell.

Explanation

To determine the internal resistance of the cell using the given potentiometer arrangement, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Given Data:**
- Length of the wire at balance point in open circuit, \( L_1 = 350 \, \text{cm} \)
- Length of the wire at balance point with external resistance, \( L_2 = 300 \, \text{cm} \)
- External resistance, \( R = 9 \, \Omega \)
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