The electric resistance is the example of plastic or pressure welding process. In this welding process wherein coalescence is produced by electric current flows through electrode and heat is generated in between electrodes. A huge quantity of current is passed through two electrodes and job is held under pressure in between electrodes. At the same time electric resistance is also made high , in order that in short time a huge quantity of heat is generated. This heat raises the metals to be weld brings in plastic stage and melt them. At this stage another condition is applied ie pressure on job.
In electric resistance welding there are no required any additional welding filler metal. The whole welding process is done by specific machine. This welding is generated by passing a large electrical current from 13000 to 33000 amp. per sq. cm. of electrode area. The voltage required (1 to 25 volts) in between the work piece which is touching each other face. The simple formula is followed by this welding i.e
H = I2RT
H defines total heat is generated in jouls.
I indicates current in ampere passing through electrodes.
R defines resistance in ohm of the conductors.
And T is time period in seconds, which is basically fraction of seconds for which current flows through the electrodes.