Circuits and Circuit Theory

81.The power is measured in terms of decibles in case of

1. electronic equipment
2. transformers
3. current transformers
4. auto transformers

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82.The product of apparent power and cosine of the phase angle between circuit voltage and current is

1. true power
2. reactive power
3. volt-amperes
4. instantaneous power

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83.The purpose of a parallel circuit resonance is to magnify

1. current
2. voltage
3. power
4. frequency

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84.The r.m.s. value and mean value is the same in the case of

1. triangular wave
2. sine wave
3. square wave
4. half wave rectified sine wave

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85.The r.m.s. value of a sinusoidal A.C. current is equal to its value at an angle of _________ degrees.

1. 90
2. 60
3. 45
4. 30

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86.The r.m.s. value of alternating current is given by steady (D.C.) current which when flowing through a given circuit for a given time produces

1. the more heat than produced by A.C. when flowing through the same circuit
2. the same heat as produced by A.C. when flowing through the same circuit
3. the less heat than produced by A.C. flowing through the same circuit
4. none of the above

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87.The r.m.s. value of half wave rectified sine wave is 200 V. The r.m.s. value of full wave rectified AC. will be

1. 282.8 V
2. 141.4 V
3. 111 V
4. 100 V

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88.The r.m.s. value of pure cosine function is

1. 0.5 of peak value
2. 0.707 of peak value
3. same as peak value
4. zero

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89.The ratio of active power to apparent power is known as factor.

1. demand
2. load
3. power
4. form

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90.The reactance offered by a capacitor to alternating current of frequency 50 Hz is 20 Q. If frequency is increased to 100 Hz, reactance becomes _________ ohms.

1. 2.5
2. 5
3. 10
4. 15

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