You must maintain a certain range of voltage and current in order to deposit the weld metal properly and achieve penetration into the parent metal to get a sound weld. Also the speed at which the deposition is achieved. Also the size of the welding rod or element is a function of how much electrical energy you are able to deliver.

If it's an arc welding machine, electricity produces the heat to weld metals together.

No electricity, no welding

It doesn't



Unless it's dark