Question

The potential difference between the terminals of a cell in open circuit is 2.2 volts. With
resistance of 5 ohm across the terminals of a cell, the terminal potential difference is
1.8 volt. The internal resistance of the cell is
1)10/9ohm
2)9/10ohm
3)12/7ohm
4)7/12ohm

I want full explanation of answer ​

Answer 1

ANSWER -: 10/9ohm

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=2/1.8Ω

⟹r= 10/9Ω

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Answer 2

Answer:

10/9 ohm is the correct answer of this question