Answer / therion

Because copper has more free electrons than aluminium but
not as much as gold or silver.

Answer / deepak thakur

since copper has high current carrying capacity..
it has low resistance..
it is of smaller in size then aluminium...

Answer / arul

The electrical capacity of any type of cables/wires are
depending on the heat withstand capacity of the material
wich can be calculated with the product of square of
current, Resistance of the material and Total time for flow
of current. I2RT. Resistance again can be calculated as
R=rho*L/A where rho is the resistivity, L is the length and
A is the area of cross section. So for a fixed current flow
and fixed Length of wire the area of cross section of the
cable is directly propotional to the resistivity.
resistivity of copper is 1.68x10 power -8 and that of Pure
Aluminum is 2.82x10 power -8. So.. for a specific current
flow, an aluminum cable size shall be 1.7 times that of
copper cable. This also is not recommented as the Aluminum
resistivity varries with the alloys and even with casting.
2.5 times the size of copper can be recommented for
Aluminum cables. Also as the temporature expansion of
Aluminum is 3 times that of copper. So all the termination
and joining areas shall be treated more sensible that of
copper.

Answer / tariq

Copper has less specific resistance than that of Aluminum.......

Answer / kevin fowke

Copper has a lower resistance than aluminium so for the
same cross sectional area a copper cable will have less
power loss.

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