Question

A Zener of breakdown voltage $V _{ Z }=8\, V$ and maximum zener current, $I _{ ZM }=10 \,mA$ is subjected to an input voltage $V _{ i }=10 \,V$ with series resistance $R =100\, \Omega$. In the given circuit $R _{ L }$ represents the variable load resistance. The ratio of maximum and minimum value of $R_{L}$ is ______

Answer 1

$I =\frac{2}{100}=20\, mA$
$V _{ L }= I _{ L } R _{ L }$
$8=10 \times 10^{-3} \times R _{ L _{\max }}$
$\frac{4}{5} \times 10^{3}= R _{ L _{\max }}$
$800= R _{ L _{\max }}$
$I = I _{ Z }+ I _{ L }$
$I _{ L }=10 \,mA$
If $I _{ Z }=0$
$I _{ L _{\max }}=20 mA$
$V _{ L }= I _{ L _{\max }} \times R _{ L _{\min }}$
$\frac{8}{20} \times 10^{3}= R _{ L _{\min }}$
$400= R _{ L _{\min }}$
$\frac{ R _{ L _{\max }}}{ R _{ L _{\min }}}=\frac{800}{400}=2$