A potential divider circuit is connected with a dc source of 20 ~… - Vidyadip

MCQ

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 $P Q$ to just glow the LED is ............. cm.

A
$2$
B
$3$
C
$4$
✓
$5$

✓

Answer

Correct option: D.

$5$

d
(Image)

$PR=20cm$

$\mathrm{~V}_{\mathrm{PQ}}=\frac{1}{4} \times \mathrm{R}_{\mathrm{PR}}$

$\ell_{\min }(\mathrm{PQ})=\frac{1}{4} \times 20$

$=5 \mathrm{~cm}$

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