In arc welding, an electric arc between an electrode and workpiece converts electrical energy into intense local heat.

A first power estimate is

$$P=VI,$$

where $V$ is arc voltage and $I$ is welding current.

For $V=24\ \mathrm V$ and $I=180\ \mathrm A$,

$$P=24\times180=4320\ \mathrm W.$$

Only part of this electrical power becomes useful heat in the workpiece, so welding heat input also depends on process efficiency and travel speed.

Different arc processes arrange electrode and shielding differently. A consumable wire electrode can supply filler continuously; a nonconsumable electrode can sustain the arc while filler is added separately if needed.

The hot weld pool must be protected from surrounding air. Shielding gas, flux or slag limits reaction with oxygen, nitrogen and moisture while the metal is molten or very hot.

Electrical variables influence more than total heat. Current strongly affects melting rate and penetration; arc voltage relates to arc length and heat distribution; travel speed determines how long energy is deposited per unit weld length.

Stable arc transfer, shielding and torch position are therefore part of process control. A weld can have the correct nominal bead location yet contain defects if the electrical and shielding conditions do not maintain a stable protected pool.