Final answer:
Arc blow is caused by magnetic forces, a component of the electromagnetic force, which includes both magnetic and electrical forces. It affects welding by causing the electric arc to move uncontrollably.
Step-by-step explanation:
Arc blow is caused by magnetic forces. It occurs during welding when the magnetic field around the weld distorts the electric arc, causing it to wander or blow out from the weld area. This is problematic as it can affect the quality of the weld, making it weak or uneven. On the microscopic scale, the electromagnetic force is responsible for the interactions between atoms and molecules, encompassing both magnetic forces and electrical forces. It is a long-range force that can be either attractive or repulsive and is the same force responsible for phenomena such as static electricity and the behavior of a compass needle.
Additionally, the electromagnetic force, specifically the electric force, holds an atom together. Within an atom, the electric force is what keeps the negatively charged electrons bound to the positively charged nucleus, composed of protons and neutrons. This is different from the force that governs the structure of galaxies, which is gravity.