The first one is to look at the outside of the wire is material; standard temperature of 80 degrees and 105 degrees wire is commonly used in semi-rigid PVC jacket (except special line), smooth surface, moderate hardness, toughness, with flexural (after a 90-degree bend should not crack), outside assassination nasal odor weak; contrary, the use of secondary materials or three wire material do was surface dark with bubbles, poor toughness with flexural resistance (90 degrees bent will whiten micro-cracks), outside the assassination nose smell doctrinal.
The second is to see the color and texture of the conductor copper wire; standard conductor copper wire commonly used multi-strand bare copper or stranded tinned copper, bright surface color (was a bright copper color), good toughness can not be broken, conductor resistance (2 * 0.5 mm2 sheathed cable, for example, per kilometer resistance greater than 39 ohms); Conversely, copper clad aluminum conductor color gray, brittle (that is melting point fire with a lighter), resistance with copper conductor is more difficult to distinguish. Copper clad steel conductor color was gold flashing yellow, high toughness (not easily blown fire lighters point), the resistance of the conductor. Conductor copper coated iron color gray brass color, toughness and easy to break, the resistance of the conductor. Conductor copper clad mud color gray, toughness and easy to break (point fire with a lighter form of powder falling), the instability of the resistance of the conductor.