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Back to Practice Questions
ElectricalMeasurement & Instrumentation
PrevNext

Which is the integrating instrument?

A

Voltmeter

B

Wattmeter

C

Energy meter

D

Power factor meter

Correct Answer

тЪЩя╕П TE тАв Technical Concept & PrincipleElectricalMeasurement & Instrumentation
Option C

Energy meter

Quick Summary:

An integrating instrument is a measuring device that records the total quantity of electricity supplied over a specified period of time. Unlike indicating instruments that show instantaneous values, these meters perform a summation of the physical quantity (e.g., energy) by integrating it with respect to time.

тЪЩя╕ПTETechnical SolutionConcept & Principle
ЁЯТб Explanation

An integrating instrument is a measuring device that records the total quantity of electricity supplied over a specified period of time. Unlike indicating instruments that show instantaneous values, these meters perform a summation of the physical quantity (e.g., energy) by integrating it with respect to time.

ЁЯФв Key Formulas

E=тИл0TPdtE = \int_{0}^{T} P dtE=тИл0TтАЛPdt тАФ Represents the accumulation of energy over time TTT.

TdтИЭ╬жv╬жisinтБб(╬Ф)T_d \propto \Phi_v \Phi_i \sin(\Delta)TdтАЛтИЭ╬жvтАЛ╬жiтАЛsin(╬Ф) тАФ Driving torque in an induction-type energy meter.

тЪЩя╕П Working Principle

The energy meter operates on the principle of electromagnetic induction. The potential coil (voltage coil) produces a magnetic flux proportional to the voltage, while the current coil produces a flux proportional to the load current; these fluxes induce eddy currents in a rotating aluminum disc, creating a torque proportional to the instantaneous power (P=VIcosтБб╧ХP = VI \cos \phiP=VIcos╧Х). A braking magnet provides a counter-torque, and the disc rotation is geared to a counting mechanism that accumulates the product of power and time, тИлPdt\int P dtтИлPdt, effectively measuring total energy in kWh.

ЁЯУМ Key Points
  • тЦ╕

    Integrating instruments calculate the time-integral of the measured quantity.

  • тЦ╕

    The reading of these instruments depends on both the magnitude of the quantity and the time duration.

  • тЦ╕

    Energy meter (kWh meter) and Ampere-hour meter are common examples.

  • тЦ╕

    They typically utilize a mechanical counting mechanism or an electronic pulse accumulation circuit.

тЬЕ Advantages
  • тЦ╕

    Provides cumulative data over long durations.

  • тЦ╕

    Essential for billing and commercial utility management.

тЭМ Disadvantages / Limitations
  • тЦ╕

    Cannot provide instantaneous readings of parameters.

  • тЦ╕

    Subject to mechanical wear (in induction types) over time.

ЁЯЫая╕П Applications / Uses
  • тЦ╕

    Domestic and Industrial electricity billing.

  • тЦ╕

    Battery state-of-charge estimation (Ampere-hour meters).

ЁЯУД Additional Information
  • тЦ╕

    Voltmeter, Wattmeter, and Power factor meters are classified as 'Indicating Instruments' because they provide the instantaneous value of the measured quantity at the moment of observation.

  • тЦ╕

    An Integrating instrument does not require continuous observation to know the total value.

ЁЯУК Diagram / Illustration
Energy Integration Formula
E=тИл0TP(t)dtE = \int_{0}^{T} P(t) dtE=тИл0TтАЛP(t)dt
where EEE is Total Energy (kWh)
P(t)P(t)P(t) is Instantaneous Power (W)
тЬЕ

C is correct тАФ The energy meter is an integrating instrument that records the total electrical energy consumed over time by calculating the integral of power.

Core Concepts Used
Click any tag to open in AI Tutor
Electromagnetic Induction Integration of Power Measuring Instrument Classification
ЁЯТб EXAM TIP

In exams, remember the mnemonic 'I-I-R': Indicating (Voltmeter), Integrating (Energy meter), Recording (Graphic meter).

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