Question

A zener diode having zener voltage $8\, V$ and power dissipation rating of $0.5\, W$ is connected across a potential divider arranged with maximum potential drop across zener diode is as shown in the diagram. The value of protective resistance $R_{p}$ is ....... $\Omega$.

Answer 1

$P=V i$
$0.5=8 i$
$i=\frac{1}{16} A$
$E=20=8+i R_{P}$
$R_{P}=12 \times 16=192\, \Omega$