By doing so, weld current and force is focused into the small area of the projection, and heat is obtained from the resistance to the flow of the welding current. Due to this heat, the projections collapse and the parts are weld together. Another successful welding technique is capacitor discharge stud welding, which uses weld studs or specially formed bolts for welding instead of projections.
The definition of inert is slow or having no action or power to move. An example of inert is a slug that is standing still. having inertia; without power to move, act, or resist. tending to be physically or mentally inactive; dull; slow.
That is called inertial and the first law of motion is also known as the law of inertia. Inertia is defined as the tendency of an object to remain at rest or of moving until an external force acts on it. Object having heavier mass has larger inertia. The mass of an object is a measure of its inertia.