Question

The internal resistances of two cells shown are $0.1\Omega$ and $0.3\Omega$. If $R=0.2\Omega$, the potential difference across the cell:

• A. $B$ will be zero
• B. $A$ will be zero
• C. $A$ and $B$ be $2V$
• D. $A$ well be $>2V$ and $B$ will be $<2V$

Answer 1

The correct option is A $B$ will be zero

Applying Kirchhoffs voltage law across the circuit assuming current I we have :

$-\left(0.2\right)I-\left(0.3\right)I+2V-\left(0.1\right)+3V=0$

$\Rightarrow 0.61=4$

$\Rightarrow I=\frac{40}{6}=\frac{20}{3}\Omega$

For Potential difference across $B$, moving across it we have :

$V_1-\left(0.3\right)\frac{20}{3}+2V=V_2$

$\Rightarrow V_1-2V+2V=V_2$

$\Rightarrow V_1=V_2$

So potential difference across $B$ is $0$