Oh okay so when a short happens there is a high amount of current flowing through the hot conductor through egc completing the circuit and those high amps would be more than what the breaker allows causing it to trip , when there is no egc And theirs a short we could complete that circuit
If there is no EGC, and there is a short to any piece of metal that should normally not be energized, that piece of metal will be come energized when the ungrounded conductor contacts it. It will carry a voltage difference between it and the actual ground. If a human body touches this energized piece of metal, as well as a non-energized conductive material, that human body will carry the current and get shocked. This is what we want to avoid.
Connecting the EGC to any device that has a metal housing, means that there is a path for return current to flow back to the panelboard, and trip the breaker, thus turning the circuit OFF, and de-energizing the metal housing.
Any non-energized piece of metal or conductive material that has a chance of becoming electrically energized, needs to be bonded to the equipment grounding system. The EGC system itself gets bonded to the actual ground via the grounding electrode at the service disconnect, as well as to the neutral of the electrical service. The building steel and the foundation are also bonded to the EGC system, so throughout the building, non-energized metal and concrete remains non-energized.
If you had plastic housing instead of metal housing on a device, plastic would not get energized when the ungrounded wire faults to it. This is why you often see two prong plugs on devices that have plastic housing.