The specification of the wire is the line side - the cross-sectional area of the wire, in square millimeters, referred to as square or square - this sentence has been reduced to two words "line".The arrangement of the lines is leaping and there is no rule to follow. For example, there are 1 square wire, 1.5 square wire, but no 2 square wire; there are 2.5 square wires, but there are no 3 square and 3.5 square wires. 

Fortunately, the line of household wires does not exceed 10 square meters, and there are only five kinds of wires within 10 square meters, so it is not difficult to remember: 1 square, 1.5 square, 2.5 square, 4 square, 6 square. 

The thicker the line, the higher the current carrying capacity of the wire - the current carrying capacity of the wire determines the amount of current that can be passed through the circuit, so the key to our choice of wire is the current carrying capacity. When counting the current carrying capacity, you should not only focus on one socket, but should consider the operating current of all the sockets in the same circuit.

There are many types of wires, I have not counted them in detail, but dozens of them are always there. However, there are usually only four types of home use: BV line, BVR line, BVVB line and RVV line.

The wire laying form in which the wires are buried in the wall and underground through the threading pipe is called "concealed". Instead of burying it deeply, it puts the wires on the wall and the surface of the ground, which is called "dressing." All concealed wires, and some surface mounts - are installed through the wire slot instead of being directly exposed to the air, using BV wire and BVR wire.

These two wires are relatively cheaper, but because of the insufficient strength of the insulation layer, they cannot be used directly in the air. The BV line is a single-strand line, commonly known as "hard line"; the BVR line is a multi-strand line, commonly known as "soft line." These two lines can be arbitrarily chosen, and there is not much difference in use - there is a small difference, but because the line is too small, it can almost be ignored, and will not be described in detail here.

Of course, the price is not the same, the BV line is a bit cheaper.