Resistance Welding

What is resistance welding which “joins metal to metal”? How can two metals be joined together?

The word “resistance” in “resistance welding” means to resist against certain movement forward. It is associated with heating as in the case of friction heat when a brake is applied.

As seen in the resistance welder model, figure on the right page, electric current is applied while a pressure is applied. When the electric current tries to advance in a metal, a heat is generated by the resistance of the metal itself and the resistance at the joining section.
The joining section between two metals, in particular, will generate more heat because of higher resistance, and as a result, the two metals are melted and joined together. This method of joining two metals utilizing resistance heat is called resistance welding.