What do you mean by internal resistance, e.m.f. (electromotive force) and terminal potential difference of a cell? Derive a relation between the three. How will you determine it?

Explanation

### Step-by-Step Solution

1. **Definitions**:
- **Internal Resistance (r)**: This is the resistance offered by the electrolyte of the cell to the flow of current. It is a measure of how much the cell resists the flow of electric current internally.
- **Electromotive Force (e.m.f., E)**: This is the potential difference between the two terminals of a cell when no current is flowing (open circuit). It represents the energy supplied by the cell per unit charge.
- **Terminal Potential Difference (V)**: This is the potential difference across the terminals of the cell when current is flowing (closed circuit). It is the voltage available to the external circuit.

2. **Relation Derivation**:
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