When your laptop loses power or doesn’t start up, one reason could be that the AC adapter you use to plug your laptop into an electrical outlet isn't working. Here’s how to find out:

First, is the AC adapter plugged in to a working wall outlet? Some outlets are turned on or off by a switch, and some outlets may be disabled by a blown circuit breaker. Test the outlet by plugging a radio or desk lamp into it.

If you're sure the wall outlet is delivering electricity, move on to examine the adapter. Look for obvious signs of damage: Burn marks are a bad sign, as are any cuts in the AC cable coming in or the DC cable going out. If you see this sort of problem, you should retire the adapter and purchase a replacement unit.

Now check that the adapter is properly connected. In most designs, the adapter is a rectangular box that sits between two cables. The plug at the end of one cable must be connected to a wall outlet and the other end to the adapter. (This cable can usually be disconnected from the adapter to allow use of cables with different types of plugs —a polarized two-prong plug like those used in the United States, Canada, Japan, and many other parts of the world, a two- or three-prong round pin connector like those used in some parts of Europe, or a three-spade angled connector used in other areas.)

Make certain that both cables are properly connected to the adapter, that the AC end is plugged in to a working wall outlet, and that the DC end is connected properly to the power input on the laptop.