Question

A Zener of breakdown voltage $V_Z=8V$ and maximum zener current, $I_{ZM}=10mA$ is subjected to an input voltage $V_i=10V$ 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

Answer: 2

$I=\frac{2}{100}=20mA$
$V_L=I_L{R}_L$
$8=10\times 10^{-3}\times R_{L_{\max }}$
$\frac{4}{5}\times 10^3=R_{L_{\max }}$
$800=R_{L_{\max }}$
$I=I_Z+I_L$
$I_L=10mA$
If $I_Z=0$
$I_{L_{\max }}=20mA$
$V_L=I_{L_{\max }}\times R_{L_{\min }}$
$\frac{8}{20}\times 10^3=R_{L_{\min }}$
$400=R_{L_{\min }}$
$\frac{R_{L_{\max }}}{R_{L_{\min }}}=\frac{800}{400}=2$