Final answer:
Shortening the arc length in welding can cause the electrode to melt due to an increase in temperature resulting from lower resistance and higher power dissipation in the circuit.
Step-by-step explanation:
If the arc length is shortened during a welding process, metal transferring across the gap may cause the electrode to melt. This is due to the fact that the shortened arc leads to an increase in temperature as a result of lower resistance in the electrical circuit. As per Ohm's Law, the power dissipation is represented by P = V2/r, meaning that as resistance decreases, the power dissipation increases, which causes higher temperatures. This can lead to further ionization and increase in power dissipation, creating a hazardous cycle that results in the melting of the electrode, especially when high voltages are used.