When traveling to foreign countries from the U.S., there are things to consider when using any plug-
To use plug-
Adapters are available as individual, sets, or universal adapters. Universal adapters provide multiple configurations for a number of countries in a single adapter.
You may want to shop for adapters ahead of your trip. Common adapters can be found at airports and train stations at reasonable prices.
For specific information on voltages and frequencies in different countries see Mains Electricity by Country by Wikipedia.
Hair dryers sold in the U.S. can be used with 240 volts in a foreign country without a transformer. Before you leave, place the switch in the off position, use a screwdriver to turn the selector from the lower voltage (125 volts) to the higher voltage (250 volts). Actual listed voltages can vary slightly.
This prevents you from selecting the “high” setting on the hair dryer. Since the foreign input voltage (240 volts) will be double the U.S. voltage (120 volts), the “low setting” will act as the “high” setting. There will be no “low” setting in the foreign country.
No transformer needed
Phone charger voltage label
U.S. To Great Britain and Africa
U.S. To Europe and Asia
U.S. To Australia and New Zealand