What operating principle does a torque indicating system utilize?

A torque indicating system operates on the principle of measuring the twisting action on a power transmitting device, such as a shaft or gear. This twisting action, or torque, is the rotational force that causes an object to rotate about an axis. When torque is applied to a shaft, it creates a torsional stress that can be measured by torque sensors or indicators. These systems often use various methods, such as strain gauges, to convert the twisting action into an electrical signal that is proportional to the amount of torque being applied.

Understanding this principle is crucial for monitoring and controlling the performance of engines and other machinery, ensuring they operate within safe and efficient torque limits. The other options relate to different physical principles; the linear motion of components pertains to translational movement, magnetic field interaction relates to electromagnetism, and thermal expansion involves changes in size due to temperature, none of which directly describe the operation of a torque indicating system.