Which of the following tools is essential for safely disconnecting an appliance from a power source?

The voltage tester is essential for safely disconnecting an appliance from a power source because it helps ensure that there is no electrical current flowing through the appliance before work begins. Using a voltage tester allows technicians to verify that the power has been turned off and that it is safe to proceed with disconnection or repair. This tool is crucial for preventing electrical shocks and ensuring the safety of the technician while working on the appliance.

While the other tools mentioned may have their specific uses during appliance service, they do not directly address the immediate safety concerns of disconnecting power. Pliers may assist in handling certain components, safety goggles provide eye protection during various tasks, and a screwdriver set is necessary for removing screws or panels. However, none of these tools can confirm the absence of electrical current like a voltage tester can, making it a vital tool in the context of safely working with electrical appliances.