Take the case of a lamp bulb. When applied an Alternating current across it.. it basically goes on and off 50 times in a second [in india atleast.. we get 50Hz]. Now, it means that the filament gets hold and cold continuously. From wikipedia: so.. is alternating current more damaging for appliances as compared to DC? Almost all electronic devices convert AC to DC.. so they are out of the question... i'm thinking about the rest of the simple devices.. like light bulbs and stuff.