The balancing length for a cell is 560 cm in a potentiometer experiment. When an external resistance of 10 $\Omega$ is connected in parallel to the cell, the balancing length changes by 60 cm. If the internal resistance of the ceil is ${N \over {10}}$ $\Omega$ , where N is an integer then value of N is .............
Answer (integer)
12
Solution
Let the emf of cell is $\varepsilon$ internal resistance is 'r' and potential gradient is x.
<br><br>When only cell connected :
<br><br>$\varepsilon$ = 560x .....(1)
<br><br>After connecting the resistor
<br><br>${{\varepsilon \times 10} \over {10 + r}}$ = 500x ....(2)
<br><br>from (1) and (2)
<br><br>56 = 50 +5r
<br><br>r = ${6 \over 5}\Omega$ = ${N \over {10}}\Omega$
<br><br>$\Rightarrow$ N = 12
About this question
Subject: Physics · Chapter: Current Electricity · Topic: EMF and Internal Resistance
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