CBSE Class 12 Physics 2023 Outside Delhi Set 1 Paper - Question ...

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

R

. When current '

T

' is drawn from the cell, the potential difference across the electrodes of the cell drops to

{\V}

. The internal resistance '

r

' of the cell is

$(\;{E-V}/{E}) R$
$(\;{E-V}/{R})$
$\;{(E-V) R}/{I}$
$(\;{(E-V)}/{V}) R$

Solution:

Since,

\;\; {\I}=\;{E}/{R+r}

So,

{\E}= {\I} r+ {\V}

∴ \;\; r=\;{ {\E}- {\V}}/{ {\I}}

Or,

\;\; r= (\;{E-V}/{V}) R \;\; [ ∵ {\V}= {\IR}]

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