cables

http://en.wikipedia.org/wiki/Ampacity

Ampacity, also described as current rating or current-carrying capacity, is the RMS electric current which a device can continuously carry while remaining within its temperature rating. The ampacity of a cable depends on:

• its insulation temperature rating;
• Ampacity, also described as current rating or current-carrying capacity, is the RMS electric current which a device can continuously carry while remaining within its temperature rating. The ampacity of a cable depends on:
• its insulation temperature rating;
• conductor electrical properties for current flow;
• ability to dissipate heat, which depends on cable geometry and its surroundings;
• ambient temperature
The ampacity for a power cable is thus based on physical and electrical properties of the material & construction of the conductor and of its insulation, ambient temperature, and environmental conditions adjacent to the cable. Having a large overall surface area may dissipate heat well if the environment can absorb the heat.conductor electrical properties for current flow;
• ability to dissipate heat, which depends on cable geometry and its surroundings;
• ambient temperature

The ampacity for a power cable is thus based on physical and electrical properties of the material & construction of the conductor and of its insulation, ambient temperature, and environmental conditions adjacent to the cable. Having a large overall surface area may dissipate heat well if the environment can absorb the heat.

Pleas give the reference when you take matter from the web page

http://en.wikipedia.org/wiki/Ampacity

even writing Wiki here is OK.