Sweden uses the Europlug (Type C & F) for electricity, with two round prongs. So what kind of electric transformer or adapter do Sweden travelers need for the 220 volts coming out of the electrical outlets?
It's not too hard to find out what kind of plug or converter you need for electrical outlets in Sweden. Most laptops will automatically work with 220 volts (check the back of your laptop for power input markings.) That means you'll only need an adapter to change the shape of your power plug to fit into an outlet in Sweden.
These power adapters are relatively cheap.
If you bring small appliances, you should double-check. The shape adapter may not be enough. While basically all personal electronics in recent years will accept both voltages, some older, smaller appliances don't work with the strong 220v current in Europe. Check if the label near the appliance's power cord shows 100-240v and 50-60 Hz. If it does not, you will need a "step-down transformer" (also called a converter).
The converter will reduce the 220 volts from the outlet to provide just 110 volts for the appliance. These converters cost a little more than simple adapters.
Tip: Don't bring any type of hair dryer to Sweden - they are awfully hard to match up with a suitable converter due to astronomical power consumption. Rather check if your accommodation in Sweden has one in the room, or just buy a cheap one locally.