Someone remembers the words "phase", "zero", "grounding" from a course of school physics. But to explain in practice why in an electrical circuit there are a phase and zero it is difficult. Try to understand a question.
To understand electrics bases, it is not obligatory to go deep into technical details of an electrical circuit. The nobility, ways of transfer of electric current which are single-phase or three-phase is enough. The three-phase network is when electricity arrives on three wires, and on one has to return back, to a source of current which can be the transformer, the electric counter. The single-phase network is when electricity arrives on one wire, and on another comes back to the power supply. Such system is called an electrical circuit, and its bases pass at physics lessons.
Remember – the electrical circuit consists of a source, consumers, connecting wires and other elements. In any source of current also negatively charged particles "work" positively. They collect on different poles of a source, one of which becomes positive, and another negative. If to connect poles of a source, there is electric current. Under the influence of the electrostatic force of a particle acquire the movement only in one direction.
For a start review an example of single-phase network: the apartment in which electricity to a teapot, the microwave, the washing machine arrives on one wire, and back to a current source - on other wire. If to open such chain, then, electricity will not be. The wire giving current is called phase or a phase, and a wire on which current returns – zero or zero. If the network three-phase, electricity arrives on three wires, and to return also on one. Three-phase networks more often happen in houses of country type. If in such network to open one wire, then, on other phases the current will remain. That is, the phase in electrics is a wire which gives current from the power supply, and zero is a wire which takes away current back, to the power supply. If not to provide to current a constant chain – there were accidents on the line, there was a wire breakage, then, devices can just stop working or will be burned with an overstrain in an electrical network. In electrics this phenomenon is called "a distortion of phases". If zero broke, tension can change both in the greatest, and in the smallest party.