For not that long ago people rarely travelled with electrical gadgets. Maybe the odd hair dryer or electrical razor. These days everyone has something with them that they need to plug in or charge... cell phones, I-Phones, I-Pads, MP3 Players, laptops, cameras, etc; The fact that countries have different outlets and voltage has become more of a problem than it was for 10 years ago. Hotels, such as the Rival Hotel (where I work), often offer electrical adapters for guests to borrow... but, because of the high demand, they do tend to run out of them. I highly recommend purchasing an international adapter, especially if you are travelling to several countries on your trip. They are relatively inexpensive, neither bulky nor heavy and easily purchased at any airport or hardware store. This way you don't run the risk of being without one on your trip!
Outlet in Sweden (and most of EU)
The voltage in Sweden is 230v and the plugs/outlets are the standard round two-prong Euro-plug used in most Western European countries (not UK or Ireland). Click here for maps showing voltage and outlet-types in different countries.