What must be the current in a circuit if potential difference across a cell is equal to the emf of the cell.

Options

A. 0
B. 10A
C. `0.5` A
D. 105 A

Explanation

To determine the current in a circuit when the potential difference across a cell is equal to the EMF of the cell, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definitions**:
- EMF (Electromotive Force) of a cell is the maximum potential difference when no current is flowing.
- The potential difference (V) across the cell is the voltage available when the cell is connected in a circuit.

2. **Set Up the Equation**:
- When a cell discharges, the potential difference (V) across the terminals of the cell can be expressed as:
\[ V = E - I \cdot r \]
where:
- \( V \) = potential difference across the cell
- \( E \) = EMF of the cell
- \( I \) = current flowing through the circuit
- \( r \) = internal resistance of the cell

3. **Apply the Given Condition**:
- According to the question, the potential difference \( V \) is equal to the EMF \( E \):
\[ V = E \]

4. **Substitute into the Equation**:
- Substitute \( V \) with \( E \) in the equation:
\[ E = E - I \cdot r \]

5. **Simplify the Equation**:
- Rearranging the equation gives:
\[ I \cdot r = 0 \]

6. **Solve for Current \( I \)**:
- Since \( r \) (internal resistance) is a positive value, the only way for the product \( I \cdot r \) to equal zero is if:
\[ I = 0 \]

7. **Conclusion**:
- Therefore, the current \( I \) in the circuit must be zero when the potential difference across the cell is equal to the EMF of the cell.

### Final Answer:
The current in the circuit must be **0 Amperes**.

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