Junior Engineer (Electrical/Electronics) MCQs – Series 8 (Q91-100)
Q91. A Wheatstone bridge is primarily used to accurately measure:
- A) Very high resistance only
- B) Frequency
- C) Inductance only
- D) Medium-value unknown resistance using the null deflection method
Answer: D
A Wheatstone bridge balances four resistive arms to find an unknown resistance with high precision when the galvanometer shows zero deflection.
Q92. The main purpose of a current transformer (CT) in measurement is to:
- A) Step down high current to a safe, standard value for use with ordinary ammeters
- B) Step up current for protection purposes
- C) Measure voltage directly
- D) Improve the circuit’s power factor
Answer: A
A CT reduces large primary currents to a proportionally smaller, standardized secondary current suitable for connecting to standard meters and relays.
Q93. In a moving-iron instrument, the deflection is proportional to:
- A) The square of the current (giving a true RMS reading)
- B) The current directly
- C) The voltage only
- D) The supply frequency
Answer: A
Moving-iron instruments respond to the force proportional to I², making them suitable for both AC and DC RMS measurements.
Q94. A megger is an instrument used to measure:
- A) Load current
- B) Supply frequency
- C) High insulation resistance
- D) Low resistance values
Answer: C
A megger applies a high test voltage to measure very high insulation resistance of cables and windings, detecting insulation deterioration.
Q95. The pointer-deflection error caused by friction in an analog indicating instrument can be reduced by using:
- A) A higher operating current
- B) Jewel bearings or taut-band suspension
- C) A lower supply voltage
- D) A larger, heavier pointer
Answer: B
Jewel bearing or taut-band suspensions minimize mechanical friction, reducing frictional error in the pointer movement.
Q96. The main advantage of a digital multimeter over an analog multimeter is generally its:
- A) Higher accuracy and easier, unambiguous readability
- B) Inability to measure AC quantities
- C) Guaranteed lower purchase cost
- D) Complete elimination of the need for calibration
Answer: A
Digital multimeters typically offer higher measurement accuracy and a clear numeric display, reducing reading (parallax) errors compared to analog meters.
Q97. Kelvin’s double bridge is specifically designed for the precise measurement of:
- A) Very low resistance values
- B) Capacitance
- C) Inductance
- D) Very high resistance values
Answer: A
Kelvin’s double bridge eliminates the effect of lead and contact resistance, making it suitable for measuring very low resistances accurately.
Q98. A Cathode Ray Oscilloscope (CRO) is mainly used to:
- A) Measure resistance directly in ohms
- B) Display and analyze the shape, amplitude and frequency of a waveform
- C) Measure power factor directly
- D) Measure only steady DC voltage
Answer: B
A CRO visually displays the time-varying waveform of a signal, allowing measurement of amplitude, frequency, phase, and distortion.
Q99. The household energy meter used to measure electrical energy consumption typically operates on the principle of:
- A) Thermal expansion
- B) Electromagnetic induction (rotating aluminium disc)
- C) Electrostatic deflection
- D) Piezoelectric effect
Answer: B
Induction-type energy meters use eddy currents induced in a rotating aluminium disc, whose rotation speed is proportional to power, to register energy consumed.
Q100. A DC potentiometer used for precision voltage measurement operates on the principle of:
- A) Comparing the unknown voltage with a known reference at a null (balance) point
- B) Resistive heating of a wire
- C) Electromagnetic force on a coil
- D) Direct deflection proportional to current
Answer: A
A potentiometer measures voltage by balancing it against a known standard cell voltage at a point of zero galvanometer deflection, giving high accuracy without drawing current from the source.
Pages:
1 2 3 4 5 6 7 8 9 10 11 12
