Question 313: Current Electricity

Question

Two cells of emf 2E and E with internal resistance r
1
and r
2
respectively are connected in series to an external resistor R (see figure). The value of R, at which the potential difference across the terminals of the first cell becomes zero is
![](https://imagex.cdn.examgoal.net/1kmli9pci/038df869-03f0-45c1-83e4-8d3e3b3bff48/7e7a6720-8b8e-11eb-8bc4-81bde7104d98/file-1kmli9pcj.jpg)

Accepted Answer

$l = {{3E} \over {R + {r_1} + {r_2}}}$
${V_A} = {V_B}$
$2E = i\,{r_1}$
$2E = {{3E} \over {R + {r_1} + {r_2}}}{r_1}$
$2R + 2{r_1} + 2{r_2} = 3{r_1}$
$R = {{{r_1}} \over 2} - {r_2}$
![](['https://imagex.cdn.examgoal.net/1kps8ghdv/1d693452-2c42-4eb2-b92c-dea19a4ecf58/42621c40-caa6-11eb-8996-937117edafc4/file-1kps8ghdw.png', 'https://imagex.cdn.examgoal.net/1kps8gu09/4df73e09-6f4d-446c-a865-4a5381a336f2/4c21fd90-caa6-11eb-8996-937117edafc4/file-1kps8gu0a.png'])

Answer

r
1
$-$ r
2

Answer

${{{r_1}} \over 2} - {r_2}$

Answer

${{{r_1}} \over 2} + {r_2}$

Answer

r
1
+ r
2

Current Electricity

Two cells of emf 2E and E with internal resistance r 1 and r 2 respectively are connected in series to an external resistor R (see figure). The value of R, at which the potential difference across the terminals of the first cell becomes zero is

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