In this topic, you study the definition and theory of the Indicating instruments.
These instruments actually indicate i.e. provide “instantaneous” value of the quantity under measurement. At another instant. the value may change and thus the position of the pointer will also change on the calibrated scale. The a.c. ammeter or voltmeter gives instantaneous/rms value of the current or voltage under measurement. Similarly, deflection of pointer of a speedometer indicates the speed of the automobile at that moment/instant.