question_answer

Figure shown a DC voltage regulator circuit, with a Zener diode of breakdown voltage = 6V. If the unregulated input voltage varies between 10 V to 16 V, then what is the maximum Zener current? [JEE Main 12-4-2019 Afternoon]

A) 2.5 mA                        

B) 3.5 Ma

C) 7.5 mA                        

D) 1.5 mA

Correct Answer: B

Solution :

Maximum current will flow from zener if input voltage is maximum. When zener diode works in breakdown state, voltage across the zener will remain same. \[\therefore \]\[{{V}_{across4k\Omega }}=64\] \[\therefore \]Current through\[4K\Omega =\frac{6}{4000}A=\frac{6}{4}mA\] Since input voltage = 16V \[\therefore \]Potential difference across \[2K\Omega =10V\] \[\therefore \] Current through \[2k\Omega =\frac{10}{2000}=5mA\] \[\therefore \] Current through zener diode \[=({{I}_{S}}-{{I}_{L}})=3.5mA\]