Question 70 QMED02 - Electrician-Refrigerating Engineer

The Correct Answer is C **Explanation for C (electric shock if the tool is shorted):** A ground connection (often the third prong on a plug) is a safety feature designed to provide a low-resistance path for fault current to follow, rather than passing through the user. If an internal electrical component, such as a wire, comes into contact with the metal casing of the tool (a "short" or fault), the ground wire immediately conducts this current to the earth. This causes the circuit breaker or fuse to trip, de-energizing the tool and preventing the metal casing from becoming live, thereby eliminating the risk of a severe or fatal electric shock to the person holding the tool. **Why the other options are incorrect:** * **A) grounding the plastic case through a short:** Tools that require grounding typically have a metal, not plastic, casing. Plastic is an insulator and cannot be grounded. Furthermore, the goal is to prevent grounding the *user*, not to facilitate grounding the case, which is the mechanism of protection. * **B) burning out the motor from an overload:** Overloads (drawing too much power under normal operating conditions) and motor burnout are primarily prevented by thermal protection devices (like internal circuit breakers) within the motor, or by properly rated fuses/breakers in the main circuit, not by the ground connection itself. The ground protects the user, not the motor. * **D) overloading the motor from a short:** A direct short circuit typically causes a sudden, massive surge of current which trips the main circuit breaker instantly. While this protects the motor from being damaged by the massive current, the primary function of the safety ground is to protect the **user** from the resulting dangerous voltage on the casing before the breaker trips. Protection against current-based damage (overload/short) is the function of the fuse/breaker; protection against shock is the function of the ground wire.