Question

Find the equivalent resistance of the network shown in figure between the points $\text{A}$ and $\text{B}$.

• A. If $V_A>V_B$, net resistance is $10\Omega$.
• B. If $V_A>V_B$, net resistance is $5\Omega$.
• C. If $V_A<V_B$, net resistance is $20\Omega$.
• D. If $V_A<V_B$, net resistance is $5\Omega$

Answer 1

The correct option is B If $V_A>V_B$, net resistance is $5\Omega$.

Let the potentials at $\text{A}$ and $\text{B}$ be $V_A$ and $V_B$ respectively.

If $V_A>V_B$, the diode is forward biased and the current will flow as shown in the figure below.


So, both the resistance will be in parallel connection.

$\therefore R_{eq}=\frac{10}{2}=5\Omega$

If $V_A<V_B$, the diode is reverse biased and the current will flow as shown in the given figure.


Thus, the current will flow through only one $10\Omega$ resistance.

$\therefore R_{eq}=10\Omega$

Hence, options $\left(\text{B}\right)$ is the correct answer.