Question

derive the equation for internal resistance of cell​

Answer 1

Answer:

V = ε – Ir.

Explanation:

Consider the circuit. The cell can be modified with an emf ε and the internal resistor with resistance r which is connected in series. An external load resistor with resistance R is also connected across the circuit. The terminal potential difference represented as V is defined as the potential difference developed between the positive and negative terminals of the cell when current flows through the circuit.

V = V+ + V- – Ir. This is the voltage drop accomplished due 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 across the circuit, ε is the emf, I is the current flowing through the circuit, r is internal resistance.

Usually internal resistance of a cell is not considered because ε >> Ir. The value of internal resistance changes from cell to cell.

Hope it helps you