For the two cells having same EMF E and internal resistance $r$, the current passing through the external resistor $6 \Omega$ is same when both the cells are connected either in parallel or in series. The value of internal resistance $r$ is \_\_\_\_ $\Omega$.

JEE Main · 2026 · 28 Jan 2026 · Shift 1 · Current Electricity

For the two cells having same EMF E and internal resistance

r

, the current passing through the external resistor

6Ω

is same when both the cells are connected either in parallel or in series. The value of internal resistance

r

is ____

Ω

Answer: (D)

For series connection:

i_{1} = \frac{2 E}{6 + 2 r}

For parallel connection:

i_{2} = \frac{E}{6 + \frac{r}{2}}

Since

i_{1} = i_{2}

\frac{2 E}{6 + 2 r} = \frac{E}{6 + \frac{r}{2}}

Simplifying:

12 + r = 6 + 2 r

Therefore:

r = 6 Ω

JEE Main · 2026 · 28 Jan 2026 · Shift 1 · Single correct option