The Connection of copper and aluminum wires
If you plan to conduct electricity at home, to mount the wiring, you will at least need to know what wire is made of aluminum and copper, and if the need arises in the connection of conductors of various kinds, then it is not a direct conventional stranding is strictly prohibited!
Now, about all detail and in order.
In any Institute or vocational school for future installers and electricians are taught the simple truth that aluminum and copper wires together is not recommended. In actual fact all that is happening really has nothing to do with the electrics in principle. Many question and many people ask on the forums and on the web something like "Why you can not connect wires of different metals, and connect then to pass current ".
If such a game will ask an ordinary cleaner, it is an original question obviously get boxed in. Electrician will tell you that twisting will warm up and eventually the contact will weaken you at some stage will remain without electricity at all.
If you want a more complete answer to your question "Why " there are several different, it is not contradictory, but partially explains all the processes occurring in places such connection.
1)you should Start with the fact that any contact has a conductor resistance and as a result a little heated. The coefficient of thermal expansion of copper is different from this parameter aluminum. Therefore when current flows both dilate with different parameters and then coming back to normal again with different parameters. Time after time the twist begins to become loose, the contact resistance starts to grow, and the heat also starts to grow. Sometimes it comes to this, that occurs even arc discharge, which ultimately brings the strands of the operating status.
2)it is worth noting that aluminum wires have the oxide layer and it is a poor conductor of electricity since the beginning, if the twist is not welded, in any case, even the two aluminum wires in the strand are pretty decent resistance. And if in contact more and different metals, the process of heating and oxidation comes with much more heat and it usually it ends in thoranam aluminum wire from twisting.
3)There is a third justification for such inconsistencies in the mix. Aluminum and copper wire in spool form a galvanic couple, where the current flows and it is inconceivable to imagine that the twist was not otgoral. Again, these all ends of the heating and the arc and as a result you remain without electricity. Perhaps you are interested in the answer to another question now. Where is the truth about the connection
the First description of the process to make sense, but in fact is not a full explanation of the situation. The second is also partially true, if you know what the temperature coefficient of expansion of copper– 16,6*10-6m/(m*gr. Celsius); aluminium– 22,2*10-6m/(m*gr. Celsius); steel– 10,8*10-6m/(m*gr. Celsius). The essence is that if you link this parameter, the steel wire and aluminum is not generally recommended to twist, because they are generally in the parameters of thermal expansion is very distinguishable.
If the different coefficients of expansion, a solid clip in the slats decides everything and then no problems with this you not feel.
Oxide film Yes it is, but great weather it does not build on heating and strong impact.
The true theory is a "galvanic couple" and of course the oxidative processes. And copper and aluminum wire are oxidized, heated and dissolved much faster if they are in a pair are connected. Occurs by the exchange of particles of metals, naturally everything is destroyed and spoiled. A full description would take a whole book, in fact it was not and need to read, the main thing to learn is exactly one! To connect aluminum wire with copper directly is not recommended!
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