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Test: Voltage Regulation Using Zener Diode - UPSC MCQ


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10 Questions MCQ Test - Test: Voltage Regulation Using Zener Diode

Test: Voltage Regulation Using Zener Diode for UPSC 2024 is part of UPSC preparation. The Test: Voltage Regulation Using Zener Diode questions and answers have been prepared according to the UPSC exam syllabus.The Test: Voltage Regulation Using Zener Diode MCQs are made for UPSC 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Test: Voltage Regulation Using Zener Diode below.
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Test: Voltage Regulation Using Zener Diode - Question 1

The percentage voltage regulation (VL) is given by_________

Detailed Solution for Test: Voltage Regulation Using Zener Diode - Question 1

The change in the output voltage from no load to full load condition is called as voltage regulation, where VNL is the voltage at no load condition. It is used to maintain a nearly constant output voltage. If the regulation is high, the output voltage is stable.

Test: Voltage Regulation Using Zener Diode - Question 2

The limiting value of the current resistor used in a Zener diode (when used as a regulator)

Detailed Solution for Test: Voltage Regulation Using Zener Diode - Question 2

When the input voltage is maximum, the load current is minimum, the Zener current should not increase the maximum rated value. Therefore there should be a minimum value of resistor.

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Test: Voltage Regulation Using Zener Diode - Question 3

When the regulation by a Zener diode is with a varying input voltage, what happens to the voltage drop across the resistance?

Detailed Solution for Test: Voltage Regulation Using Zener Diode - Question 3

 When the input voltage varies, the input current also varies. This makes more current to flow in the diode. This increase in the current should balance a change in the load current. Hence the voltage drop increases across the resistor.

Test: Voltage Regulation Using Zener Diode - Question 4

In the given limiter circuit, an input voltage Vi=10sin100πt is applied. Assume that the diode drop is 0.7V when it’s forward biased. The zener breakdown voltage is 6.8V.The maximum and minimum values of outputs voltage are _______

Detailed Solution for Test: Voltage Regulation Using Zener Diode - Question 4

With VI= 10V when maximum, D1 is forward biased, D2 is reverse biased. Zener is in breakdown region. VOMAX=sum of breakdown voltage and diode drop=6.8+0.7=7.5V. VOMIN=negative of voltage drop=-0.7V. There will be no breakdown voltage here.

Test: Voltage Regulation Using Zener Diode - Question 5

Determine the maximum and minimum values of load current for which the Zener diode shunt regulator will maintain regulation when VIN=24V and R=500Ω. The Zener diode has a VZ=12V and (IZ)MAX=90mA (Iz)min = 3 mA

Detailed Solution for Test: Voltage Regulation Using Zener Diode - Question 5

The current through the resistance R is given by, I=(VIN-VZ)/R= (24-12)/500=24mA. (IL)MAX=I-(IZ)MIN=24-3=21mA .This current is less than (IZ)MAX. So, we assume that all the input current flows through the Zener diode. Under this condition, (IL)MINis 0mA.

Test: Voltage Regulation Using Zener Diode - Question 6

Determine the minimum value of load resistance that can be used in the circuit with (IZ)Min=3mA. The input voltage is 10V and the resistance R is 500Ω. The Zener diode has a VZ=6V 0and (IZ)MAX=90mA.

Detailed Solution for Test: Voltage Regulation Using Zener Diode - Question 6

The I=(VIN-VZ)/R=(10-6)/500=8mA. (IL)MAX=I-(IZ)MIN=8-3=5mA. (RL)MIN=VZ/(IL)MAX=6/5m=1.2KΩ.

Test: Voltage Regulation Using Zener Diode - Question 7

A Zener regulator has to handle supply voltage variation from 19.5V to 22.5V. Find the magnitude of regulating resistance, if the load resistance is 6KΩ. The Zener diode has the following specifications: breakdown voltage =18V, (IZ)Min=2µA, maximum power dissipation=60mW and Zener resistance =20Ω.

Detailed Solution for Test: Voltage Regulation Using Zener Diode - Question 7

(PZ)MAX/rZ=(IZ)MAX2 . So, (IZ)MAX =60m/20=54.8µA. IL=VO/RL=18/6000=3mA.
RMAX=(VMin-VZ)/[( IZ)Min+( IL)MAX]=(19.5-18)/(2µ+3m)=500Ω.
RMin=(VMAX-VZ)/[( IZ)MAX+( IL)Min]=(22.5-18)/(54.8m+3m)=77.8Ω.

Test: Voltage Regulation Using Zener Diode - Question 8

A transistor series regulator has the following specifications: VIN=15V, VZ=8.3V, β=100, R=1.8KΩ, RL=2KΩ. What will be the Zener current in the regulator circuit?

Detailed Solution for Test: Voltage Regulation Using Zener Diode - Question 8

We know, VO=VZ-VBE=8.3-0.7=7.6V. VCE=VIN-V0=15-7.6=7.4V. So, IR=(VIN-VZ)/R=(15-8.3)/1.8m=3.72mA. IL=VO/RL=7.6/2000=3.8mA. IB=IL/ β=3.8mA/100=0.038mA. Finally, IZ=IR-IB=3.72-0.038=3.682mA.

Test: Voltage Regulation Using Zener Diode - Question 9

When is a regulator used?

Detailed Solution for Test: Voltage Regulation Using Zener Diode - Question 9

The regulator has following limitations: 1.It has low efficiency for heavy load currents 2. The output voltage changes slightly due to Zener impedance. Hence, it is used when there are small variations in load current and input voltage.

Test: Voltage Regulation Using Zener Diode - Question 10

 A transistor in a series voltage regulator acts like a variable resistor. The value of its resistance is determined by _______

Detailed Solution for Test: Voltage Regulation Using Zener Diode - Question 10

The principle is based on the fact that a large fraction of the increase in input voltage appears across the transistor so that the output voltage remains to be constant. When input voltage is increased, the output voltage also increases which biases the transistor towards less current.

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