Physics Electronics PMC 2021
PMDC Verified Question 475 of 494

A transformer is commonly used prior to the rectification stage in a DC power supply to:
A
Step up the voltage
B
Step down the voltage
C
Equalize the voltage
D
None of these
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Step down the voltage
Concept:

Standard household mains voltage is typically very high (e.g., 220V AC), while most digital and solid-state electronic devices operate on low DC voltages (e.g., 5V to 12V).

Solution:

The primary function of the transformer in a consumer electronic power supply is to step down the high AC mains voltage to a safe, low AC level before passing it through the rectifying diodes and filters.

Why other options are incorrect:

  • Step up is incorrect because electronic devices do not require hundreds or thousands of volts to operate.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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