Change 220 to 110

Answer 1

Depends on whether you mean as a source or as a device.

To convert a source, you would generally use a step-down transformer or an electronic equivalent, known as a "voltage converter". There are hundreds of devices made for that purpose, many of which are designed for specific national receptacle standards.

To convert a device, there is sometimes a switch for selecting the input voltage between 220 and 110, although a growing number of devices automatically handle inlet voltages from 240 volts to 110 volts. In other devices you might need to find the manuals and have the necessary tools to open it and reconfigure a jumper or switch or other settings -- something not always designed for "users", and not always possible without re-engineering the unit.

Answer 2

To change 220 to 110, you need to halve the value. 220 ÷ 2 = 110.