Will my iMAC work on a 220 current?

Do you mean a 220V as in a power in Europe? Then,
Check your adaptor. It will tell you the input voltage. If it sates that the range of the input voltage in 100V-240V then YES you can plug in your adapter into a 220V outlet.
Please note that some people advise that you plug in the adapter into the power before plugging it into the computer.