Question

3) using potentiometer derive an expression for internal resistance of a cell?

Answer 1

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Answer 2

An expression for internal resistance of cell:

The terminal potential difference signified as V is well-defined as the potential difference developed between the positive and negative terminals of the cell when current streams through the circuit.

V = V+ + V- – Ir. This is the voltage drop accomplished owing to the internal resistance.

We know that

ε = V+ + V-. = I (R + r).

ε = IR + Ir.

= V + Ir

V = ε – Ir.

So, V = ε – Ir, where V is the potential difference through the circuit, ε is the emf, I is the current flowing through the circuit, r is internal resistance.

Usually, the internal resistance of a cell is not measured because of ε >> Ir. The value of internal resistance varies from cell to cell.

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