True or False: A grounded wire is connected to metal appliance cases

The ground wire, formally known as the equipment grounding conductor (EGC) or protective earth (PE), is a critical safety feature. It is intentionally connected to the non-current-carrying conductive parts of an appliance, such as its metal case or chassis. In the event of an internal insulation failure where a "hot" (live) wire touches the metal case, the ground wire provides a low-impedance path for the fault current to flow back to the source. This large current flow will trip the circuit breaker or blow the fuse, de-energizing the circuit and preventing the metal case from becoming dangerously electrified, thus protecting users from electric shock.

B. False: This is incorrect. Failing to connect the ground wire to the metal case would defeat its primary safety purpose, creating a severe shock hazard if an internal fault were to occur.

1. IEEE Std 142-2007, "IEEE Recommended Practice for Grounding of Industrial and Commercial Power Systems" (The Green Book).

Section 1.4.2, "Shock hazard," explains that grounding non-current-carrying metal enclosures of equipment provides a low-impedance path for fault current, causing the overcurrent protective device to operate and clear the fault, thereby removing the shock hazard. This confirms the direct connection.

2. University of Illinois at Urbana-Champaign, Division of Research Safety, "Electrical Safety Program."

Section 6.2, "Grounding," states, "The metal case of the equipment is connected to the ground wire. If the 'hot' wire touches the case, the current will flow to the ground instead of through a person, and the fuse will blow."

3. University of Washington, Environmental Health & Safety, "Electrical Safety Manual."

Section 4.1, "Grounding," describes how connecting a machine or appliance to the ground creates an intentional low-resistance path to earth. This path is designed to carry fault current safely to the ground, causing the circuit protection to open. This principle relies on the connection to the appliance's conductive case.