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CBSE Class 12 Physics 2023 Outside Delhi Set 1 Paper

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Question : 4 of 35
Marks: +1, -0
A cell of emf E is connected across an external resistance RR. When current ' TT ' is drawn from the cell, the potential difference across the electrodes of the cell drops to VV. The internal resistance ' rr ' of the cell is
Solution:     👈: Video Solution
Since,     I=ER+r\;\; I = \frac{E}{R+r}
So, E=Ir+VE = I r + V
∴    r=E−VI\therefore \;\; r = \frac{E-V}{I}
Or,     r=(E−VV)R    [∵V=IR]\;\; r = \left(\frac{E-V}{V}\right) R \;\; [\because V = I R]
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