Q 12-03-216JEE MainJEE Main 2021 (27 Aug, Shift 1)Easy
Five identical cells each of internal resistance $1\ \Omega$ and emf $5$ V 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?
Answer: (A) $1\ \Omega$
Series: $I_s = \dfrac{25}{R + 5}$. Parallel: $I_p = \dfrac{5}{R + \frac{1}{5}}$.
$$25\left(R + \frac{1}{5}\right) = 5(R + 5) \Rightarrow 20R = 20 \Rightarrow R = 1\ \Omega$$
Solution by Sreeraj P, M.Sc Physics