Question

1. The potential difference between the terminals a cell in open circuit is 2.2volt. With resistance of 5ohm across the terminals of a cell, the terminal potential difference is 1.8 volt. Calculate the internal resistance.​

Answer 1

Explanation:  

10 /9 Ω

potential difference across the cell in open circuit is the emf of the cell.

Hence, emf E=2.2V

when, circuit is closed, potential difference across cell is given by V=E−Ir

And,

I= E/ R+r

Hence, V= E− Er/ R+r

⟹ V= ER/ R+r

⟹ 1.8= 2.2×5 /5+r

⟹9+1.8r=11

⟹ r= 2/  1.8  Ω

⟹ r= 10/9  Ω

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