Question

The potential difference between points $\text{A}$ and $\text{B}$ in the circuit shown in figure will be

• A. $1\text{V}$
• B. $2\text{V}$
• C. $-3\text{V}$
• D. $-\frac{40}{9}\text{V}$

Answer 1

The correct option is D $-\frac{40}{9}\text{V}$


For the given circuit, effective emf will be

$E_0=10-5=5\text{V}$ [cell with reverse polarity]

And effective resistance of given series combination is given by

$R_0=2.5+2.5+15+25=45\Omega$

so, current in the circuit,

$I=\frac{E_0}{R_0}=\frac{5}{45}=\frac{1}{9}\text{A}$

Further, on going from $\text{A}$ to $\text{B}$ in anticlockwise, we get,

$V_A+(25\times \frac{1}{9})+(15\times \frac{1}{9})=V_B$

$\therefore V_A-V_B=-\frac{40}{9}\text{V}$

Hence, option $\left(d\right)$ is correct.