What type of transducer utilizes electrical resistance variation to sense strain?

A metallic strain gauge is the correct choice because it operates based on the principle of electrical resistance variation in response to mechanical strain. When a metallic strain gauge is deformed, its length changes, which in turn alters its electrical resistance. This change in resistance can be precisely measured and is directly proportional to the amount of strain experienced by the material it is attached to.

Strain gauges are commonly used in various applications to monitor stress and strain in structural components, providing critical data for analysis in engineering and design. This ability to convert mechanical deformation into a measurable electrical signal is what makes them particularly valuable in instrumentation and control systems.

Other types of sensors, like capacitive sensors, work on different principles, such as measuring changes in capacitance due to displacement or pressure changes; pneumatic sensors rely on air pressure variations; and thermocouples are designed to measure temperature based on the voltage generated at the junction of two different metals. These principles differ significantly from the resistance-based operation of metallic strain gauges.