Question

Two resistors of resistances $200\text{k}\Omega$ and $1\text{M}\Omega$, respectively from a potential divider with outer junctions maintained at potentials of $+3\text{V}$ and $-15\text{V}$. What is the potential at the junction $\text{X}$ between the resistors?

• A. $+1\text{V}$
• B. $0\text{V}$
• C. $-0.6\text{V}$
• D. $-12\text{V}$

Answer 1

The correct option is B $0\text{V}$

Let $I$ be the current flowing through the resister from $+3\text{V}$ to $-15\text{V}$.

Apply KVL between two extreme points

$3-(200\times {10}^3\times I)-({10}^6\times I)=-15$

$\Rightarrow I=\frac{18}{1.2\times {10}^6}=15\times {10}^{-6}\text{A}$

For potential at $\text{X}$,

$15\times {10}^{-6}=\frac{3-V_x}{200\times {10}^3}$

$\Rightarrow V_x=0\text{V}$

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

Why this Q? Current flows from higher potential to lower potential.