If damping torque is not provided in an instrument
If damping torque is not provided in an instrument the pointer will oscillate about its final deflected position for quite sometime before coming to rest.
This is because when the pointer is deflected, it has kinetic energy which will cause it to continue moving back and forth until the energy is dissipated.
The oscillations will gradually decrease in amplitude due to the internal friction and air resistance, but without damping torque, the pointer may continue to oscillate for several seconds or even minutes, making it difficult to read the correct value on the scale.
Damping torque is provided in many instruments to overcome this problem. Damping torque refers to the opposing torque that is applied to the pointer to reduce its oscillations and bring it to rest quickly.
The damping torque is usually provided by a fluid (such as air or oil) or a metallic disc, which opposes the motion of the pointer and dissipates its kinetic energy.
This helps to ensure that the pointer comes to rest quickly, allowing for accurate readings to be taken.