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1)

A Zener diode, having a breakdown voltage equal to 15 V  is used in a voltage regulator circuit shown in the figure. The current  through the diode is 

Answer:

Option D

Explanation:

 

 

For R=$1k \Omega$

$i_{1}=\frac{15}{1}mA=15 mA$

$R=250 \Omega$

$i_{250}=\frac{20-15}{250}=\frac{5}{250}=20mA$

$i_{Zener}=20-15=5mA$