For a cell, terminal potential difference is 2.2 V when the circuit is open. If it reduces to 1.8 V when connected to a resistance of 5 Ω, internal resistance r of cell is:
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For a cell, terminal potential difference is 2.2 V when the circuit is open. If it reduces to 1.8 V when connected to a resistance of 5 Ω, internal resistance r of cell is:

G1 Physics · Accepted Answer

Step 1: Open-circuit voltage is emf E = 2.2 V. Step 2: Load current I = 1.8/5 = 0.36 A. Step 3: Internal drop E−V = Ir ⇒ r = 0.4/0.36 = 10/9 Ω.