Quote:
Originally Posted by electeng
65. By which a meter after checking with no current returns to its previous state
i think it is damping torque,
controlling torque is responsible for correct position in case of current flowing, if not then pointer is placed at zero position due to damping torque
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Right answer is controlling torque. Its the controlling torque that takes the pointer back to the zero position, not the damping torque, whose function is just to reduce fluctuations / oscillations in the reading.
Controlling torque does two functions. It balances the deflecting torque (so that the deflection is always the same for a particular value of current or voltage) and it also brings back the pointer to the zero position when the current or voltage is removed. The controlling torque increases till it is not equal to the deflection torque and at that point the pointer comes to rest.
Damping torque is to reduce the oscillations of the pointer till it comes to the rest. The pointer oscillates around its final value of reading due to inertia, to reduce/eliminate these fluctuations, damping torque is used.
Hope you will get my point.