For the two cells having same EMF E and internal resistance $r$, the current passing through the ext

Question

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 $\_\_\_\_$ $\Omega$.

Accepted Answer

In series, $i_{i} = \frac{2E}{6 + 2r}$In parallel, $i_{2} = \frac{E}{6 + \frac{r}{2}}$$${i_{1} = i_{2} \Rightarrow \frac{2E}{6 + 2r} = \frac{E}{6 + \frac{r}{2}} }{12 + r = 6 + 2r }{r = 6\Omega}$$

Question

Options

Solution

More Current Electricity and Electrical Instrument Questions