the elect. course says silver is the best conductor, is gold the best? is that the reason some connectors are gold plated?

 

Ok, this is a loaded question. If you are talking about economically, its copper.

Silver is a very good conductor. Gold is a very easy metal to plate and very good marketing ploy.

Here you go: Silver is the best conductor of heat and electricity:
http://www.gold-eagle.com/editorials_01/haynes111401.html

 

Gold oxidizes less than silver so it's better for contacts.
Platinum oxidizes even less but it's generally more expensive than gold.

 

In μΩ*cm, the resistivities are

Silver 1.59
Copper 1.72
Gold 2.44
Aluminum 2.8

Thus, you can see that the resistivity of copper is only about 5% less than that of silver. Because the cost is so much less, this makes copper the overwhelming favorite for most conductors. Silver tarnishes too much. Copper also has some oxidation problems, which is why more expensive constructions often gold-plate the copper conductors, as gold resists oxidation/corrosion quite well. As Ghar mentioned, platinum would be good too, but the price of platinum is somewhere between ridiculous and disgusting.

 

Does It matter In airline,or military equipment that needs to be reliable
or does ,as we always hear the stockholder has to make a profit.The
mission statment of most companies,We work for the stock holder.
Has your pension plan caused harm to anyone,or does the public care.

 

A problem with gold plating is Soldering issues. A good description can be found here. http://en.wikipedia.org/wiki/Gold_plating

 

Loosewire, if you read the link I posted, you will see a new type of silver "wire" that the military is using. It uses silver coated ceramic, cooled with liquid nitrogen to have zero resistance. Its called High Temp Superconductor. Zero Ohms at -195c. Where most superconductors require liquid helium temperatures -276c to achieve zero ohms.

Neat.

HTS wire, a ceramic compound made of certain metal oxides that exhibit zero electrical resistance at the temperature of liquid nitrogen (-195 C, -320 F) have now been perfected, and commercial production has begun. Traditional superconductors function only at the temperature of liquid helium (-276 C, -450 F), an expensive gas requiring cumbersome equipment. The higher temperature of liquid nitrogen easily can be maintained by efficient mechanical refrigerators; hence the name, high-temperature superconductors (HTS). HTS wire carries 140 times the electrical current of copper wire and relies on silver for its flexibility, conductivity, and strength.

 

The silver is also an insulator in this context, being much higher resistance.