JEE MAIN - Physics (2021 - 27th August Morning Shift - No. 17)
Five identical cells each of internal resistance 1$$\Omega$$ and emf 5V are connected in series and in parallel with an external resistance 'R'. For what value of 'R', current in series and parallel combination will remain the same?
1 $$\Omega$$
25 $$\Omega$$
5 $$\Omega$$
10 $$\Omega$$
Explanation
$${i_1} = {{25} \over {5 + R}}$$
$${i_2} = {5 \over {R + {1 \over 5}}}$$
$${i_1} = {i_2} \Rightarrow 5\left( {R + {1 \over 5}} \right) = 5 + R$$
4R = R
R = 1$$\Omega$$
$${i_2} = {5 \over {R + {1 \over 5}}}$$
$${i_1} = {i_2} \Rightarrow 5\left( {R + {1 \over 5}} \right) = 5 + R$$
4R = R
R = 1$$\Omega$$
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