The force applied to a strain gauge causes it to bend and change its

• A. Resistance
• B. Capacitance
• C. Inductance
• D. Conductivity

Answer: (A)

When a strain gauge is bent by force, its electrical resistance changes. This happens because the foil or wire inside the gauge is stretched or compressed, altering its length and cross-sectional area. Since resistance is given by R = ρL/A, a stretch increases L and reduces A, both pushing the resistance upward. The tiny change is detected by a Wheatstone bridge and converted into a voltage signal the system can read. The sensitivity is described by the gauge factor, GF = (ΔR/R) / ε, which explains how small strains produce measurable resistance changes.

Capacitance and inductance aren’t what a typical strain gauge is designed to measure, and while conductivity is related to resistance (conductivity is inversely related to resistance), the sensor output is based on resistance change, not direct changes in capacitance, inductance, or conductivity.