Updated: 11/13/2018 by Computer Hope
Power surge

Alternatively known as a line surge or power surge, a surge is a short, fast rise in voltage that inherently causes an increase in electrical current or vice versa. Exclusive to electrical circuits, a power surge can cause damage or impairment to a computer or other devices.

For example, the standard voltage rating on a landline in the United States is 120 volts. If this rating is exceeded for more than three nanoseconds, it would be considered a surge. Any shorter duration is considered a spike.


Users can prevent damage from power surges with surge protectors.


A surge can also travel over a phone line. An unprotected modem may also cause damage to your computer.

What causes a surge?

The most common cause of a surge is an electrical storm lightning bolt that strikes a device connected to a power, phone, cable, or another wire. For example, a lightning bolt could strike a satellite dish. Then, the electricity could travel over the wire connected to that dish into a home and damage any electrical device that is not protected.

Other examples of what causes a power surge include ESD, an appliance powering on or off, and physical damage to external power lines.

How does a power surge damage a computer?

Everything in a computer is powered by electricity. As we mentioned above, the standard delivery for wall sockets in the U.S. is 120V. However, a lightning strike can be upward of many millions of volts. This extremely excessive current generates a lot of excess heat, causing integrated circuits (among other things) to melt and be destroyed.

Brownout, Current, Landline, Power failure, Power terms, Spike