Question 211: Semiconductors and Logic Gates

Question

A potential divider circuit is connected with a dc source of $$20 \mathrm{~V}$$, a light emitting diode of glow in voltage $$1.8 \mathrm{~V}$$ and a zener diode of breakdown voltage of $$3.2 \mathrm{~V}$$. The length (PR) of the resistive wire is $$20 \mathrm{~cm}$$. The minimum length of PQ to just glow the LED is _________ $$\mathrm{cm}$$.

Accepted Answer

For minimum length of $$P Q$$,
$$\begin{aligned}
& \mathrm{V}_{	ext {diodes }}=1.8+3.2=5 \mathrm{~V} \
& 	herefore \quad I_{P Q}=\frac{20}{20} 	imes 5 \
& =5 \mathrm{~cm} \
&
\end{aligned}$$

Semiconductors and Logic Gates

Integer / Numeric Answer Type