Workshop Technology
Piercing is an operation of cutting

A number of holes evenly spaced in a regular pattern on a sheet of metal
A cylindrical hole in a sheet of metal by the punch and the die
A flat sheet to the desired shape
A hole (other than cylindrical) in a sheet of metal by the punch and the die

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Workshop Technology
For arc welding

Alternating current with high frequency is used
Alternating current with low frequency is used
Direct current is used
Any one of these

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