Electric characteristics and contact area features of melting when making and breaking contacts

We studied the contact current after Vc=Um of electric contacts during `initial arc'. Using the transient current switch circuit (diodes, resistor and capacitor parallel to the contacts), the melting phenomena of cross-rod electrodes of 0.5mm in diameter were separately observed from arc discharge. Measurement of electric characteristics and observation of the contact area features by laser microscope were able to confirm the existence of conduction current due to the remaining metal contact. This would means that conductive currents flow just after Vc=Um, arcing currents join them one by one, and only the arcing current flows at the last.