Purchase wire and cable must go to the regular business to buy.  The quality of any commodity is good or bad. The commodity market sells all sorts of dazzling, the slightest mistake is likely to buy counterfeit products. The following is to provide you with the purchase of wire and cable method:
Good quality wire, usually in the specified weight range; qualified wire copper core should be purple, shiny, soft feel. The shoddy wire copper core for purple black, yellow or white, impurities, mechanical strength, toughness is not good, a little force that will break, and wire often broken wire phenomenon. Check, as long as you peel off a wire 2cm, and then use a piece of white paper on the copper core slightly rub, if there is a black material on the white paper, indicating that the impurities in the copper core. In addition, the unqulified wire insulation layer seems thick, is actually mostly made of recycled plastic, for a long time, the insulation layer will aging cracking and leakage; manufacturers of fake wires are often "three products", but it was also identified as the origin of ready to accept either course, China manufacturing, China Province or a city manufacturing etc. This is not standard, the actual origin; due to production cost of fake wires is low, therefore, traders in the sales, often under the guise of cheap low sales, deceitful.
When you want to look at the purchase of qualified businesses, good test is very important, in order to avoid buying fake products.
Add another two points, the most important problem of shoddy wire has the following problems, 1, the wire service life is short, easy to crack aging. 2, the conductor resistance, insulation electric limit is small, carrying capacity is poor, easy to heat, waste electricity, easy to cause fire.