Question

Two junction diodes one of germanium $\left(\text{Ge}\right)$ and other of silicon $\left(\text{Si}\right)$ are connected to a battery of emf $12\text{V}$ and a load resistance $10\text{k}\Omega$ as shown in the figure. The germanium diode conducts at $0.3\text{V}$ and silicon diode at $0.7\text{V}.$ When a current flows in the circuit, the potential of terminal $\text{Y}$ will be

• A. $12\text{V}$
• B. $11\text{V}$
• C. $11.3\text{V}$
• D. $11.7\text{V}$

Answer 1

The correct option is D $11.7\text{V}$

Forward voltage across $\text{Ge}$ is,

$=12-0.3=11.7\text{V}$

Thus, potential of point $\text{Y}=11.7\text{V}$

Key note :

Since $\text{(Ge)}$ has smaller cut in voltage, it will start conducting first (assuming negligible forward resistance).

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Hence, $\left(D\right)$ is the correct answer.