question_answer

Consider the circuit, the current through the Zener diode is

A)  20 mA

B)  10 mA

C)  15 mA

D)  40 mA

Correct Answer: B

Solution :

 Consider the circuit shown below. Voltage across \[{{R}_{2}}\]is \[{{V}_{{{R}_{2}}}}={{V}_{Z}}=20\,V\] Current through\[{{R}_{2}}\]is \[I{{R}_{2}}=\frac{{{V}_{{{R}_{2}}}}}{{{R}_{2}}}=\frac{20}{2000}=\frac{1}{100}A=10\,mA\] Voltage drop across \[{{R}_{1}},{{V}_{{{R}_{1}}}}=40-20=20\,V\] \[I=\frac{{{V}_{{{R}_{1}}}}}{1000\,\Omega }=\frac{20}{1000}=\frac{2}{100}=20\,mA\] Thus, current through Zener diode \[{{I}_{Z}}=I-{{R}_{{{R}_{2}}}}=20\,mA-10\,mA=10\,mA\]