Basic Electrical Engineering

81. The main advantage of air as a dielectric material for capacitors is

1. Has a high dielectric constant
2. Is not physically dense
3. Has low loss
4. Allows for large capacitance in a small volume

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82. The main disadvantages of using short pitch winding in alternators is that it

1. reduces harmonics in the generated voltage
2. reduces the total voltage around the armature coils
3. produces asymmetry in the three phase windings
4. increases Cu of end connections.

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83. The output wave of a common-gate amplifier circuit with a pure sine-wave input

1. is in phase with the input wave.
2. lags the input wave by 90° of phase.
3. leads the input wave by 90° of phase.
4. is 180° out of phase with the input wave.
5. is inverted with respect to the input wave.

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84. The peak voltage in an ac wave is always

1. greater than the average voltage
2. less than the average voltage
3. greater than or equal to average voltage
4. less than or equal to the average voltage

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85. The period of a ac wave, in seconds is

1. The same as the frequency in hertz
2. Not related to the frequency in any way
3. Equal to 1 divided by the frequency in hertz
4. Equal to the peak amplitude in volts divided by the frequency in hertz

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86. The power drawn by the circuit whose input is 20KVA and p.f is 0.8 lagging

1. 12
2. 20
3. 16
4. 8

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87. The power factor at resonance in RLC circuit is

1. zero
2. unity
3. 0.5 lagging
4. 0.5 leading

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88. the power factor of a purely resistive circuit is

1. zero
2. unity
3. lagging
4. leading

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89. The power plant having highest efficiency is

1. Hydro
2. Thermal
3. Nuclear
4. Diesel

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90. The Q-factor of a coil is given by

1. its power factor
2. Ratio of max. energy stored & energy dissipated per cycle.
3. reciprocal of its power factor
4. ratio R/Z

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