wire powered?

Hello, i'm pretty new on this and i'm trying to know if there if a wire is powered, what should i use? i have seen you can use a toroid or something but i dont know, all i want is to know if a 220v light is on or off, how can i do it?

THANKS

P.D: Sorry for my english.

Some form of light sensor (LDR, phototransistor etc) would be the easiest and safest - no connections to harmful voltages..........

The problem with the ldr is it would have noise because it will receive light from others fonts like a lamp, I have seen i can know if a wire haves some power using a toroid but I have no idea how to make it possible.

If you positioned the LDR close to the lamp you're interested in, there shouldn't be any problems picking out your lamp from background light because it will be much brighter. If that doesn't appeal connect a neon up to the lamp circuit and use the ldr next to it inside a light proof box. Optical isolation is the way to go. You can sense the voltage in a 220V cable but the fact you're asking on here, suggests you shouldn't be going anywhere near voltages that will kill you. Keep it simple - keep the arduino away from mains..........

Where can i get the lightproof stuff? Thanks

Cardboard box wrapped in black tape ? Works for me...... ;)

I will try it, thanks