Derive an expression for internal resistance of a cell
Answers
Answer:
Consider the circuit given below. 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.
Explanation:
hope it will help u....
Answer:
Batteries and cells have an internal resistance (r) which is measures in ohm’s (Ω). When electricity flows round a circuit the internal resistance of the cell itself resists the flow of current and so thermal (heat) energy is wasted in the cell itself. In this equation (V) appears which is the terminal potential difference, measured in volts (V). This is the potential difference across the terminals of the cell when current is flowing in the circuit, it is always less than the e.m.f. of the cell.
Explanation: