Question

Two identical cells connected in series send $10\,A$ current through a $5\Omega$ resistor. When they are connected in parallel, they send $8\,A$ current through the same resistance, the internal resistance of each cell is

• A. Zero
• B. 2.5$\Omega$
• C. 10 $\Omega$
• D. 15 $\Omega$

Answer 1

Answer: (B)

2.5$\Omega$

Answer 2

For series combination $2 \xi = (5 + 2r) 10$ . For parallel combination $\xi = ( 5 + \frac{r}{2} )8$