Don’t forget to pack an extension cord and European-style adapters! – Travel packing tip #1
Since many places use either European-style plugs, or may only have one outlet per room, here’s a good travel packing tip: Always bring your own 6-8′ extension cord. One with three prongs plugs is best, since your laptop probably requires it and if you don’t need that third hole, who cares, it will still work. But if you pack a two-prong cord, and you have a three-pronged plug, you’ll be out-of-luck!
Make sure to cut or file the newer, widened ‘polarization tip’ off the one prong of the plug so it’ll plug into the old 220 V. British (round prong) tip adapters. Use the extension cord not only to bring the power closer to you (in rooms that only have 1 plug for the whole room), but also to multiply the outlets so you can charge your devices along with those of your roommate. 🙂 Many rooms will have only one plug. Even in many American hotels, there are only one or two open plugs for use! And if your travel partner has a phone, you have a phone and one more thing that requires power, somebody is going to be out of luck. While this is inexcusable, the way to solve it is to pack your own! A surge protector-type multi-outlet may be nice, but may not have a long enough cord. And they are bulky/heavy for international travel. Depending on where you are headed, you may be able to purchase a local multi-outlet surge protector or extension cord, but don’t count on it! A simple extension cord is best to keep in your bag, ready at all times.
Some people suggest breaking off the third round “pin” on the plug-in side of the extension cord (so it just has two like in the old days). Depending on your situation, and where you are traveling, and what style outlet or adapter you own, you may need to do this. It should not be dangerous since the one pin is already the ground, that returns electricity back to the wall. That third prong we are talking about is for grounding the item itself that is plugged in, so that any metal that could become energized doesn’t give you a shock. That is the only reason it was there in the first place, and honestly I have never been shocked by a power cord or by my laptop. I have used power cords with the ground pin pulled out or broken off for years without issues. Your mileage may vary. Electricians personally (and online) have both opinions on the matter. Overseas may be more on an issue because they have more sudden spikes or surges in electricity, so there may be a chance that your device may be damaged if plugged in while there is a spike.
What adaptors will you require, and are they safe or will you blow the circuit or short out your device? WikiTravel has more on the topic as does REI. If you aren’t sure about your destination, try http://worldelectricguide.com/ which list every country.
As you can see, there are many varieties of electric outlets but here are the most common. And don’t assume the voltage is correct just because the plug fits, since a Thai Type A+C socket still carries 220V and may destroy American (110V) Type A devices.
(The Wiki link above also discusses transformers and converters which is important to understand and plan for). If you need a travel converter, check out http://www.worldtravelguide.com/travel-gear/travel-voltage-converters.html
Irregular voltage or spikes/brownouts can also harm your electrical devices. Always unplug them when not in use and if going to a place with irregular voltage, consider buying or packing a surge protector as well.
Hair dryers and certain devices (such as TVs) take a large amount of electrical power and may overload the system. If in doubt, always ask. Computers and phones almost always use a “trickle-method” of charging that is not as draining as a hair dryer.
Most laptops and phones are also very good/tolerant at handling varied power, not taking too much power at once, and even able to handle 240v! The problems usually come from other devices.
How to use that new plug/converter? Check out this simple guide from USAToday: http://traveltips.usatoday.com/use-travel-adapter-1521.html
For fun, see where the world (and your destination) gets its electricity from this interactive website: http://environment.nationalgeographic.com/environment/energy/great-energy-challenge/world-electricity-mix/