CET CET Power Supplies and Electrical Safety

Question 1

What is the primary purpose of a filter capacitor placed after the rectifier in a DC power supply?

Accepted Answer

Reduce output ripple by storing charge between rectifier pulses

Answer

Increase output voltage

Answer

Protect the rectifier diodes from reverse voltage

Answer

Regulate the output against load changes

Question 2

At what frequency does the ripple voltage appear in a full-wave bridge rectifier powered by a 60 Hz AC supply?

Accepted Answer

120 Hz

Answer

60 Hz

Answer

30 Hz

Answer

180 Hz

Question 3

Which type of voltage regulator dissipates the difference between input and output voltage as heat?

Accepted Answer

Linear regulator

Answer

Switching regulator (SMPS)

Answer

Buck converter

Answer

Boost converter

Question 4

How does a zener diode function as a voltage regulator in a shunt regulator circuit?

Accepted Answer

It maintains a nearly constant voltage across it by varying the current through it within its breakdown region

Answer

It blocks reverse current to stabilize voltage

Answer

It amplifies the reference voltage

Answer

It switches on and off to regulate voltage

Question 5

In a power supply, what does a crowbar circuit do?

Accepted Answer

Immediately short the output through a thyristor (SCR) if voltage exceeds a safe threshold, blowing the fuse

Answer

Regulate output voltage under heavy load

Answer

Filter high-frequency switching noise

Answer

Provide soft-start to limit inrush current

Question 6

Which component in a linear power supply converts the AC mains voltage to a lower AC voltage suitable for rectification?

Accepted Answer

Power transformer

Answer

Bridge rectifier

Answer

Voltage regulator IC

Answer

Filter capacitor