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Analog Instruments MCQs

Practice Analog Instruments MCQs with four options, answers and explanations for focused Electronics & Telecommunication Engineering revision.

Question 1
Measurements & InstrumentationAnalog Instruments

A PMMC instrument is primarily suitable for direct measurement of?

  • ADC only
  • BAC only
  • CBoth AC and DC without any additional circuit
  • DMicrowave frequency only
Report an error
Correct Answer: A. DC only
Explanation: A PMMC movement responds to the average value and reverses torque with current direction, so it is inherently suited to DC. AC measurement requires rectification.
Reference: Standard measurements and instrumentation: analog instruments
Question 2
Measurements & InstrumentationAnalog Instruments

The deflecting torque of an ideal PMMC instrument is proportional to?

  • ACurrent through the moving coil
  • BSquare of current
  • CFrequency only
  • DResistance squared
Report an error
Correct Answer: A. Current through the moving coil
Explanation: With a uniform permanent-magnet field, PMMC deflecting torque is directly proportional to coil current.
Reference: Standard measurements and instrumentation: analog instruments
Question 3
Measurements & InstrumentationAnalog Instruments

A moving-iron instrument can normally be used for?

  • ABoth AC and DC
  • BDC only
  • CAC only above 1 MHz
  • DTemperature only
Report an error
Correct Answer: A. Both AC and DC
Explanation: Moving-iron torque depends approximately on the square of current, so its direction is independent of current polarity and it can measure AC or DC.
Reference: Standard measurements and instrumentation: analog instruments
Question 4
Measurements & InstrumentationAnalog Instruments

The scale of a PMMC instrument is approximately?

  • AUniform
  • BHighly logarithmic
  • CSquare-law crowded at upper end
  • DIndependent of current
Report an error
Correct Answer: A. Uniform
Explanation: Because deflection is proportional to current, a PMMC instrument has an approximately uniform scale.
Reference: Standard measurements and instrumentation: analog instruments
Question 5
Measurements & InstrumentationAnalog Instruments

The scale of a basic moving-iron instrument is generally?

  • ANon-uniform
  • BPerfectly uniform
  • CDigital
  • DLinear only at zero frequency
Report an error
Correct Answer: A. Non-uniform
Explanation: Moving-iron deflecting torque is nonlinear with current, so its scale is generally non-uniform and crowded near the lower end.
Reference: Standard measurements and instrumentation: analog instruments