Question

Find the potential difference $V_a-V_b$ between points $a$ and $b$ as shown below.

• A. $16\text{V}$
• B. $8\text{V}$
• C. $-8\text{V}$
• D. $-16\text{V}$

Answer 1

The correct option is C $-8\text{V}$

Using potential drop method, we can write the potentials of different points as shown in the figure.


Using $\text{KCL}:$

$2[0-(V+4)]+1[0-(V+8)]+2[0-(V+12)]=0$

$\Rightarrow -2V-8-V-8-2V-24=0$

$\Rightarrow -5V-40=0$

$\Rightarrow V=-8\text{V}$

So, potential difference across $a$ and $b$,

$\Rightarrow V_a-V_b=V-0=-8\text{V}$

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

$\text{Note}$ : Negative sign shows that potential at $b$ is higher than at $a$.