Q.31 Why the designers of ac generators try always to obtain a waveform approximating as closely as possible to that of a pure sine wave?
A. sine wave greatly simplifies the theory and calculations of ac circuits
B. The resultant of two or more quantities, varying sinusoidaly at the same frequency, is another sinusoidal quantity of the same frequency
C. Both A and B
D. rotation of generator is resemble to sine wave
Ans.: C
Q.32 Which of the following is/are correct?
A. f = PN/120
B. N = 120 f/P
C. p = P/2
D. all of the above
Ans.: D
Q.33 what will be the highest speed at which a 60 Hz generator can be operated?
A. 3000 rev/min
B. 3200 rev/min
C. 3600 rev/min
D. 3800 rev/min
Ans.: C
Q.34 Calculate frequency if the speed in revolutions per minutes of 2 pole alternator is 3000?
A. 49 Hz
B. 50 Hz
C. 51 Hz
D. 40 Hz
Ans.: B
Q.35 why it is not possible to state the value of an alternating quantity as simple as stated for a DC quantity?
A. Alternating quantity varies in magnitude and reverses its direction at regular intervals
B. the value of an alternating quantity is continuously changing
C. Alternating quantity does not varies in magnitude and reverses its direction at regular intervals
D. Both A and B
Ans.: D
Q.36 The value of the alternating quantity at a given instant or time is called___.
A. minimum value
B. instantaneous value
C. maximum value
D. fixed value
Ans.: B
Q.37 The instantaneous value__
A. varies from instant to instant
B. it is denoted by small or lower case letters
C. It indicate the value of given quantity at that given time
D. all of the above
Ans.: D
Q.38 Maximum value is the maximum value of _____attained by it in a cycle.
A. DC quantity
B. AC quantity
C. Both AC and DC
D. none of the above
Ans.: B
Q.39 Maximum value is also called ___.
A. crest value
B. peak value
C. amplitude
D. all of the above
Ans.: D
Q.40 Maximum value of ac quantity is denoted by__.
A. small letters
B. capital letters with subscript m
C. italic letters
D. any size letter
Ans.: B
Q.41 An alternating quantity over a given interval is the sum of all instantaneous values divided by the number of values taken over that interval.
A. Mean value
B. Average value
C. root mean square value
D. Both A and B
Ans.: D
Q.42 _____ is an equivalent direct current that will produce the same heat, in the same time interval, in the same resistor, as the alternating current.
A. Effective value
B. Root mean square value
C. mean square value
D. virtual value
Ans.: D
Q.43 The domestic supply voltage 230V implies that it is the ___ voltage.
A. average value
B. maximum value
C. r.m.s value
D. instantaneous value
Ans.: C
Q.44 Average value of current over the whole cycle is___
A. zero
B. maximum
C. minimum
D. infinite
Ans.: A
Q.45 what will be the average value for any periodic function having a wave symmetrical about horizontal axis over a complete cycle?
A. maximum
B. infinite
C. zero
D. minimum
Ans.: C