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ECAT Pre General Science Physics Chapter 16 Alternating Current Online Test MCQs With Answers
Question # 1
The most common source of alternating voltage is:
Choose an answer
Motor
Transformer
AC genrator
Both (A) and (C)
Both (A) and (B)
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Question # 2
In an A.C circuit with resistor only, the current and voltage have a phase angle of
Choose an answer
90
°
0
°
180
°
none of these
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Question # 3
The time interval during which the Voltage source changes its polarity once is known as:
Choose an answer
Time period T
Half the time period
Quarter the time period
Two third of the time period
None of these
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Question # 4
In which of the following components, pn-junction is used
Choose an answer
light emitting diode
photo diode
photo voltaic cell
all of these
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Question # 5
A digital system deals with quantities or variables which have
Choose an answer
only one state
only two discrete states
three discrete states
four discrete states
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Question # 6
The power factor of resonant series circuit is
Choose an answer
1
0
-1
0.5
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Question # 7
When electrons in the transmitting antenna vibrate 94000 time per second, they produce radiowaves having frequency
Choose an answer
9.4 kHz
940 kHz
94 kHz
None of these
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Question # 8
An A.C. voltmeter read 250 volts. The frequency of alternating is 50 Hz, the peak value of voltage is
Choose an answer
3525.0 volts
35.35 volts
353.5 volts
3.535 volts
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Question # 9
At resonance, the impedance of RLC series circuit is
Choose an answer
Maximum
Zero
Minimum
Determinate
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Question # 10
For a n-p-n transistor, the conventional current equation can be written as
Choose an answer
I
E
+ I
C
= I
B
I
C
- I
B
= I
E
I
C
+ I
B
= I
E
I
B
+ I
E
= I
C
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Question # 11
The total reactance of a series RLC circuit at resonance is
Choose an answer
zero
Equal to the resistance
Infinity
Capacitive
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Question # 12
If we connected the ordinary DC ammeter to measure alternating current, it would measure its:
Choose an answer
Instantaneous value
RMS value
Value averaged over a cycle
Either (B) or (C)
Either (A) or (C)
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Question # 13
The phase at the positive peak of an A.C. cycle is:
Choose an answer
0
º
90
º
180
º
0 and
Ꮨ
Ꮨ/2 and 3
Ꮨ/2
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Question # 14
The sum of positive and negative peak values is called:
Choose an answer
Instantaneous value
Peak value
Rms valuie
Peak-to peak-value
None of these
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Question # 15
The waveform of alternating voltage is a:
Choose an answer
Square
Rectangular
Saw-tooth
Sinusoidal
None of these
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Question # 16
The phase angle of a series RLC circuit at resonance is
Choose an answer
180
°
90
°
0
°
None of the these
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Question # 17
If the value of C in a series RLC circuit is increased, the resonant frequency
Choose an answer
Is not affected
Increase
Remains the same
Decreases
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Question # 18
A sinusoidally alternating voltage or current can be graphically represented by a:
Choose an answer
Vector
Rotating vector
Clockwise vector
Anticlockwise voltage vector
None of these
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Question # 19
The wave form of alternating voltage is the graph between:
Choose an answer
Voltage across X-axis and time across y-axis
Current and time
Voltage along y-axis and time along x-axis
Voltage and current
Either (B) or (D)
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Question # 20
At resonance frequency the impedance of parallel resonance circuit is
Choose an answer
Maximum
Minimum
Zero
None of the above
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Question # 21
When the emitter-base junction of a transistor is reverse biased, collector current
Choose an answer
Reverses
Increases
Decreases
Stops
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Question # 22
During the positive half-cycle in the half-wave rectification,the diode
Choose an answer
does not conduct
conducts
either of these
neither of these
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Question # 23
When the pn-junction is connected reversed biased, its resistance is of the order of
Choose an answer
few ohms
few kilo-ohms
few mega-ohms
few mili-ohms
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Question # 24
The Instantaneous value of alternative current maybe:
Choose an answer
The same as its RMS value
Greater than its Rms value
The same as its peak value
Any of these
None of these
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Question # 25
The basic circuit element in A.C. circuits are:
Choose an answer
Resistor and capacitor
Resistor and Inductor
Capacitor only
Both (B) and (C)
None of these
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Question # 26
In n-p-n transistor, emitter base junction is kept
Choose an answer
reversed
forward biased
may be reversed or may be forward biased
none of these
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Question # 27
The r.m.s. value of alternating current is equal to its maximum value at angle of
Choose an answer
60
°
45
°
30
°
90
°
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Question # 28
In RLC series circuit, resonance occurs when
Choose an answer
X
L > Xc
X
L < Xc
X
L = Xc
None of these
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Question # 29
A diode characteristic curve is a plot between
Choose an answer
current and time
voltage and time
voltage and current
forward voltage and reversed voltage
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Question # 30
The value of output resistance of OP-AMOP is of the order of
Choose an answer
few ohms
few hundred ohms
several kilo ohms
several mega ohms
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