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The given figure represents an arrangement of potentiometer for the calculation of internal resistance (r) of the unknown battery (E). The balance length is 70.0 \mathrm{~cm} with the key opened and 60.0 \mathrm{~cm} with the key closed. \mathrm{R} is 132.40 \Omega. The internal resistance (r) of the unknown cell to a correct number of significant figures. \left(\mathrm{E}_0>\mathrm{E}\right) is \mathrm{xy} .1 \Omega, The values of digit \mathrm{x}  is :

Option: 1

1


Option: 2

2


Option: 3

3


Option: 4

4


Answers (1)

best_answer

Internal resistance  r=\frac{\mathrm{R}\left[\ell-\ell^{\prime}\right]}{\ell^{\prime}}

where \ell= balanced length with key open. 

          \ell^{\prime}= balanced length with key \mathrm{K} closed

\therefore \quad r=\frac{132.40[70-60]}{60}

=\frac{132.40 \times 10}{60}=22.0666 \Omega

=22 \cdot 1 \Omega \text {. Thus } x=2

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manish

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