Do yourself a big favour, do some studying, play around with some resistors, LEDS and batteries and a digital multimeter to get a feel for voltage and current and how they interact before you even think about touching something that will carry mains voltage. Below 50 volts you should be OK, above that, especially European mains voltage, it can and will kill you given half a chance. As has been said before, if you need to ask questions at this kind of level, you're not fit to be playing with dangerous voltages.