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 V. If this rating is exceeded for more than three nanoseconds, it would be considered a surge, any shorter duration is a spike.
Tip: Users can help prevent damage from power surges with surge protectors.
Note: 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 a lightning bolt in an electrical storm that strikes a device connected to a power, phone, cable, or other 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 such as a fridge or air conditioner powering up or down, and problems with power lines such as a tree falling into a power line.
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; hence, destroying them.