CET Power Supplies and Electrical Safety Flashcards
6 cards from real CET practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 CET Power Supplies and Electrical Safety flashcards as text
What is the primary purpose of a filter capacitor placed after the rectifier in a DC power supply?
Answer: Reduce output ripple by storing charge between rectifier pulses
The filter capacitor charges to the peak voltage and slowly discharges into the load between pulses, smoothing the pulsating DC.
At what frequency does the ripple voltage appear in a full-wave bridge rectifier powered by a 60 Hz AC supply?
Answer: 120 Hz
A full-wave rectifier produces two pulses per AC cycle, so ripple frequency equals twice the supply frequency: 2 × 60 = 120 Hz.
Which type of voltage regulator dissipates the difference between input and output voltage as heat?
Answer: Linear regulator
Linear regulators pass current through a series pass transistor that drops the excess voltage as heat, making them less efficient than switchers.
How does a zener diode function as a voltage regulator in a shunt regulator circuit?
Answer: It maintains a nearly constant voltage across it by varying the current through it within its breakdown region
Operating in reverse breakdown, the zener holds a fixed voltage across itself while absorbing excess current, keeping output voltage stable.
In a power supply, what does a crowbar circuit do?
Answer: Immediately short the output through a thyristor (SCR) if voltage exceeds a safe threshold, blowing the fuse
A crowbar circuit fires an SCR to short the output when overvoltage is detected, causing the fuse to blow and protecting downstream equipment.
Which component in a linear power supply converts the AC mains voltage to a lower AC voltage suitable for rectification?
Answer: Power transformer
The power transformer steps down the mains AC voltage to the required level while also providing isolation from the AC line.