Sunday, 28 October 2012

Basic Electrical Engineering: Part-6 Objective Questions

Objective Questions From Basic Electrical Engineering:

[1] In ac circuit, the ratio of kW/kVA is
A. Power factor
B. Form factor
C. Load factor
D. Diversity factor

[2] Suppose that two ac waves have the same frequency but differ in phase by exactly 1/20 of a cycle. What is the phase difference between these two waves?
A.  18
B.  20
C.  36
D.  5.73

[3] The unit of inductance is
A. Mho
B. Hendry
C. Ohm
D. Farad

[4] What is the angular frequency of the ac signal having a frequency of 1770Hz
A.  1770 rad/s
B.  11,120 rad/s
C.  282 rad/s
D.  Data insufficient

[5] Thevenin's equivalent circuit consists of
A. Series combination of Rth, Eth, Rl
B. Series combination of Rth, Eth
C. Parallel combination of Rth, Eth, Rl
D. Parallel combination of Rth, Eth

[6] The frequency of DC supply is
A. 16 2/3 Hz
B. 60 Hz
C. 50 Hz
D. 0 Hz

[7] Load factor is defined as the ratio of
A. Max demand/ Average demand
B. Average demand/ Connected load
C. Average demand/ Max. demand
D. Connected load/ Max demand

[8] Q factor of an inductive coil is given by
A.  2p fL/R
B.  2p fr/R
C.  R/Z
D. lr/l

[9] The rms value of sinusoidal 100V peak to peak is
A. 100 V
B. 50/v2 V
C. 50 V
D. 100/v2 V

[10] Which of the following bulbs will have the least resistance?
A. 220V, 60W
B. 220V, 100W
C. 115V, 60W
D. 115V, 100W


Solution Hint:
[2] One cycle = 360�.
1/20 of cycle is 360/20 = 18�

[4] Angular frequency ? = 2pf (rad/s)

[7] Some of the important terms in power system:
Demand factor = maximum demand / Connected load
Diversity factor = Sum of individual max. demands / Max. demand on power station
The ratio of average load to the maximum demand during a given period is known as load factor.
Load Factor = Average Load / maximum demand

[8] Quality factor is the ratio of reactive power to average power (Q/P)

Qs = [I2XL]/[I2R]
Qs = XL/R
Qs = ?L/R 
Q=2p fL/R

[9] Vrms = Vm/v2


Thanks for reading....

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