Most places in Brazil like in Rio de Janeiro has a current strength of 110 volts and 60 hertz (the same as in the U.S.). There are some hotels that have 220 volts but then usually these are marked and hotels with better standards have converters. Other cities with 110V are Sao Paulo and Salvador da Bahia and there are several cities that use 220V. It is a good idea to buy a travel voltage converter at the airport.