bulb+relay+transistor=switch

how do I have to connect the Arduino with the relay,transistor and the 230v bulb in order to make a switch?

You google the problem.

[u]Here is a relay driver circuit[/u] (to drive the relay coil). Note that the relay coil requires a particular voltage, so for example, if you have a 12V relay coil you'll need a 12V power supply.

Wire the relay contacts in series with the bulb just like a [u]regular light switch[/u]. (That picture shows a battery instead of 220VAC, but the wiring is the same.) If your relay has more than one pair of contacts, connect between a "C" (common) and "NO" (normally open) terminal, assuming you want to turn the light on when the relay coil is energized. If you want to turn the light off when the coil is energized, connect to "C" and "NC" (normally closed).

PLEASE BE CAREFUL with voltages that can kill you (and your Adruino)! If you have a multimeter, measure the resistance to make sure there is no connection between the AC side and low-voltage side of the relay before applying power.

FYI - You can get a [u]solid state relay[/u] that works directly from 5V at low current, so you don't need a transistor. They are more expensive but they are much easier to wire-up. Just make sure it's rated for 220VAC or more (a solid-state DC relay won't work with AC) and make sure it can be controlled by 5V.

nick8:
how do I have to connect the Arduino with the relay, transistor and the 230v bulb in order to make a switch?

Usually you buy a relay module that includes the transistor, like this one:
http://www.gearbest.com/development-boards/pp_116113.html