Which of the following electrical events shows a sudden drop of power source that can cause a wide variety of problems on a PC or a network?

A power sag, also known as a dip, is a short-term reduction in the RMS (root mean square) voltage of the power source, typically lasting from half a cycle to one minute. This "sudden drop" forces electronic components in a PC or network device to operate below their specified voltage tolerance. This can lead to a wide variety of unpredictable problems, including system reboots, memory errors, data corruption, logic faults, and cumulative stress on hardware that can cause premature failure. Unlike a blackout, which causes a complete and predictable shutdown, the effects of a sag are more varied and often harder to diagnose.

A. Blackout: This is a complete loss of power, not a partial drop. Its primary effect is a predictable system shutdown, not the varied operational faults characteristic of a sag.
B. Power spike: This is a very brief, high-voltage event, representing a sudden increase in power, not a drop.
D. Power surge: This is a prolonged over-voltage condition, representing a sustained increase in power, not a drop.

1. IEEE Std 1159-2019

"IEEE Recommended Practice for Monitoring Electric Power Quality."

Section 4.3.2

"Sags (Dips)": Defines a sag as "A decrease to between 0.1 pu [per unit] and 0.9 pu in rms voltage or current at the power frequency for durations from 0.5 cycles to 1 min." This document technically defines a sag as a voltage drop.

Section 4.3.1

"Interruptions": Defines an interruption (blackout) as when the supply voltage decreases to less than 0.1 pu. This distinguishes a complete loss from a partial drop (sag).

2. Official (ISC)² Guide to the CISSP CBK

Fifth Edition.

Domain 3: Security Architecture and Engineering

Chapter 10: "Assess and Mitigate the Vulnerabilities of Physical Security

" Section: "Electrical Power." This section defines a sag as a "momentary low voltage" and a blackout as a "complete loss of power." It explains that sags can cause systems to crash or reboot

leading to data loss or corruption

which aligns with the "wide variety of problems."

3. NIST Special Publication 800-53

Revision 5

"Security and Privacy Controls for Information Systems and Organizations."

Control PE-11

"Power Equipment and Cabling": The discussion for this control mentions protecting against "power fluctuations (e.g.

spikes

sags)" and "power outages

" treating sags and outages (blackouts) as distinct events. The need to protect against sags implies they cause operational problems distinct from a complete shutdown.