Final answer:
A non-contact voltage tester is a protective device used by fire investigators to identify live electrical wires without direct contact, ensuring their safety during an investigation.
Step-by-step explanation:
A non-contact voltage tester is an essential tool for fire investigators when they need to determine if there is live electrical wiring within a fire-damaged structure. Unlike battery testers described in figures such as 21.13 and 21.15, which apply a load to measure terminal potential and decipher a battery's internal resistance, a non-contact voltage tester safely allows professionals to detect the presence of electricity without making direct contact with the wires themselves. This device helps prevent potential shock hazards and ensures a safe investigation environment.
Fire investigators use this type of equipment to perform a presumptive test, a process where they can assess whether electricity is still running through structural wiring post-incident. The non-contact voltage tester is a preventive measure, guarding against electrical safety risks such as shocks and additional fire hazards that may arise from compromised electrical systems. It is a part of electrical safety systems and devices designed to enhance safety by detecting live wires in a safe, contact-free manner.