CompTIA A+ Core 2 (220-1202), Domain 4, Objective 4.5 focuses on power protection — understanding the ways electrical power fails or misbehaves and the devices that shield computers and their data from the damage those events cause. Electronics are designed to run on clean, steady voltage, but the power coming out of a wall outlet is rarely perfect. Spikes, sags, and outages arrive without warning, and each one can corrupt data, crash a system, or physically destroy hardware. A technician's job is to match the right protective device to the risk, so a storm or a tripped breaker becomes a non-event instead of a lost weekend of recovery work.
In this article you'll learn the common power problems — surges, brownouts, and blackouts — and how surge suppressors, uninterruptible power supplies, and battery backup defend against them. You'll learn what joule ratings mean, how to decide when a surge protector is enough versus when a UPS is required, and how these choices protect both equipment and the data on it.
Common Power Problems
Power problems fall into a few categories that the exam expects you to recognize by name:
- Power surge (and spike) — a momentary increase in voltage above normal. A surge is a brief overvoltage; a spike is an extremely short, very high jump, such as one caused by a nearby lightning strike. Even large appliances cycling on and off can create smaller surges on a shared circuit. Surges push excess voltage into a device and can burn out power supplies and other components instantly or degrade them over time.
- Brownout — a reduction in voltage that lasts longer than a moment, also called a sag when brief. Utilities sometimes deliberately reduce voltage during periods of heavy demand, and drops also happen when too much load sits on a circuit. Undervoltage can cause systems to behave erratically, reboot unexpectedly, or stress the power supply, and repeated brownouts shorten hardware life.
- Blackout — a total loss of power. A blackout instantly kills any device without a battery, causing unsaved work to be lost and, worse, cutting power mid-write to storage, which can corrupt files or the file system.
Beyond these three, real-world power also carries electrical "noise" — electromagnetic and radio-frequency interference (EMI/RFI) from motors and other equipment — which better protective devices help filter out. But surges, brownouts, and blackouts are the core scenarios to know, because each calls for a different level of protection.