Question

Two cells $\left( e = 1.6 \times 10^{- 19}C \right)$ and $4\Omega$ connected in opposition to each other as shown in figure. The cell $2 \times 10^{- 2}\Omega$ is of emf 9 V and internal resistance 3 $15\Omega$ the cell $15.18\Omega$ is of emf 7 V and internal resistance $81.15\Omega$ . The potential difference between the points A and B is

• A. 8.4 V
• B. 5.6 V
• C. 7.8 V
• D. 6.6 V

Answer 1

Answer: (A)

8.4 V

Answer 2

: $I = \frac{\Delta\varepsilon}{r_{1} + r_{2}} = \frac{9 - 7}{3 + 7} = \frac{2}{10} = 0.2A$

Potential difference across

$\varepsilon_{1} = 9 - 0.2 \times 3 = 9 - 0.6$ $$= 8.4V$$

Potential difference across

$\varepsilon_{2};V_{AB} = \varepsilon_{2} + 0.2r_{2}$

$= 7 + 0.2 \times 7$

$7 + 1.4 = 8.4V$