In a potential transformer, the phase angle error should be

 

ELECTRICAL & ELECTRONIC MEASUREMENTS – ADVANCED LEVEL 

Q1. The primary advantage of a PMMC instrument is
A) High accuracy
B) Can measure AC directly
C) Low cost
D) No friction
Answer: A

Q2. The maximum permissible error of a class 0.5 instrument is
A) 0.5% of full scale
B) 0.05% of full scale
C) 5% of reading
D) 0.5 V absolute
Answer: A

Q3. In a moving iron instrument, the deflection is proportional to
A) Square of current
B) Current
C) Voltage
D) Flux
Answer: A

Q4. The control torque in a moving coil instrument is provided by
A) Springs
B) Permanent magnet
C) Eddy currents
D) Air friction
Answer: A

Q5. The deflecting torque in a PMMC instrument is proportional to
A) Current
B) Current²
C) Voltage
D) Magnetic flux
Answer: A

Q6. The damping torque in a PMMC is produced by
A) Eddy currents
B) Air friction
C) Spring control
D) Weight of pointer
Answer: A

Q7. A ballistic galvanometer is primarily used to measure
A) Total charge
B) Current
C) Voltage
D) Power
Answer: A

Q8. The main error in a dynamometer type wattmeter is due to
A) Temperature variation
B) Frequency variation
C) Phase angle error
D) Magnetic hysteresis
Answer: C

Q9. The driving torque of a dynamometer type wattmeter is proportional to
A) VI cos φ
B) I²
C) V²
D) Current only
Answer: A

Q10. A three-phase two-wattmeter method is applicable for
A) Balanced system
B) Unbalanced system
C) Single-phase load
D) Both AC and DC
Answer: A

Q11. In three-phase two-wattmeter method, if load is unity power factor,
A) Both wattmeters read equal
B) One reads zero
C) Both differ
D) None
Answer: A

Q12. If the load is purely reactive, the wattmeter readings in two-wattmeter method are
A) Equal and opposite
B) Both zero
C) Both equal
D) None
Answer: A

Q13. The primary function of a CT is
A) Step down current
B) Step up voltage
C) Power measurement
D) Resistance measurement
Answer: A

Q14. The primary function of a PT is
A) Step down voltage
B) Step up current
C) Measure resistance
D) None
Answer: A

Q15. The burden of a CT is expressed in
A) VA
B) A
C) Ω
D) W
Answer: A

Q16. CT ratio error occurs due to
A) Leakage flux
B) Copper loss
C) Saturation
D) All of the above
Answer: D

Q17. In a potential transformer, the phase angle error should be
A) Small for accuracy
B) Large
C) Zero
D) Unimportant
Answer: A

Q18. The frequency response of a PMMC voltmeter is limited due to
A) Inductance of coil
B) Resistance of coil
C) Damping
D) None
Answer: A

Q19. The error caused by capacitance of the voltmeter in AC circuits is
A) Phase error
B) Magnitude error
C) Both
D) None
Answer: A

Q20. The Wien bridge is primarily used for
A) Frequency measurement
B) Capacitance measurement
C) Inductance measurement
D) Resistance measurement
Answer: A

Q21. A Maxwell bridge is used to measure
A) Inductance with series resistance
B) Capacitance
C) High resistance
D) Low resistance
Answer: A

Q22. Schering bridge is used for
A) Capacitance and dielectric loss measurement
B) Inductance measurement
C) High resistance
D) Frequency
Answer: A

Q23. Kelvin double bridge is used for
A) Low resistance measurement
B) High resistance
C) Inductance
D) Capacitance
Answer: A

Q24. The main advantage of AC bridges over DC bridges is
A) Measure inductance and capacitance
B) Simplicity
C) Low cost
D) High accuracy
Answer: A

Q25. In a DC potentiometer, the standard voltage source should be
A) Highly stable
B) Low voltage
C) AC source
D) None
Answer: A

Q26. The accuracy of a digital multimeter depends on
A) ADC resolution
B) Reference voltage stability
C) Temperature coefficient
D) All of the above
Answer: D

Q27. The resolution of an n-bit ADC is
A) 1 / 2ⁿ of full scale
B) n
C) 2ⁿ
D) Full scale
Answer: A

Q28. Dual-slope integration ADC eliminates
A) Noise and ripple
B) Parallax error
C) Loading error
D) Phase error
Answer: A

Q29. The sampling theorem states
A) Sampling frequency ≥ 2 × highest signal frequency
B) Equal to frequency
C) Half frequency
D) Any value
Answer: A

Q30. The primary use of CRO is
A) Display waveform
B) Measure power
C) Measure energy
D) Current only
Answer: A

Q31. The Lissajous pattern in CRO is used to measure
A) Frequency ratio and phase difference
B) Current
C) Resistance
D) Voltage only
Answer: A

Q32. The horizontal deflection in CRO is caused by
A) Time base voltage
B) Input voltage
C) Magnetic field
D) None
Answer: A

Q33. The vertical deflection in CRO is caused by
A) Input signal
B) Time base
C) Magnetic field
D) None
Answer: A

Q34. The main advantage of digital storage oscilloscope is
A) Capture transient signals
B) Low cost
C) Analog accuracy
D) None
Answer: A

Q35. The true RMS meter measures
A) Effective value of arbitrary waveform
B) Peak value
C) Average value
D) DC only
Answer: A

Q36. Hot-wire instruments measure
A) True RMS value of AC and DC
B) Peak value
C) Average value
D) None
Answer: A

Q37. The form factor of a sine wave is
A) 1.11
B) 1.414
C) 0.707
D) 1.0
Answer: A

Q38. The peak factor of a sine wave is
A) 1.414
B) 1.0
C) 0.707
D) 1.11
Answer: A

Q39. The Q-factor of a coil is
A) ωL/R
B) R/ωL
C) L/R
D) None
Answer: A

Q40. A thermistor has
A) Negative temperature coefficient
B) Positive temperature coefficient
C) Constant resistance
D) None
Answer: A

Q41. Strain gauge works on
A) Resistance variation with strain
B) Capacitance
C) Inductance
D) Voltage
Answer: A

Q42. The gauge factor is defined as
A) (ΔR / R) / Strain
B) ΔR × Strain
C) ΔV / I
D) None
Answer: A

Q43. LVDT converts
A) Linear displacement into AC voltage
B) Voltage to displacement
C) Current to displacement
D) None
Answer: A

Q44. LVDT output is
A) AC voltage proportional to displacement
B) DC voltage
C) Current
D) Resistance
Answer: A

Q45. A Hall-effect sensor measures
A) Magnetic field
B) Pressure
C) Force
D) Temperature
Answer: A

Q46. A piezoelectric transducer converts
A) Mechanical pressure into voltage
B) Voltage into mechanical displacement
C) Temperature into voltage
D) None
Answer: A

Q47. Induction type energy meters are suitable for
A) AC only
B) DC only
C) Both AC & DC
D) None
Answer: A

Q48. The creeping in energy meters can be prevented by
A) Creep holes
B) Braking magnet
C) Shunt resistor
D) None
Answer: A

Q49. The driving torque of induction type energy meter is proportional to
A) Power
B) Current
C) Voltage
D) Speed
Answer: A

Q50. The braking torque of induction type energy meter is proportional to
A) Speed of disc
B) Voltage
C) Current
D) Power factor
Answer: A