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Electrical Engineering
Alternating Current And Voltage
Quiz 4
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Q.1
What will happen, if we connect capacitor to DC Supply.
It allows DC
It blocks DC
t rectifies
None of these
Hint: Diode is unidirectional and uncontrolled device. In rectifier circuit, diode use as a switch to convert ac to dc for rectification purpose.
Q.2
An inductor of inductance 22.0 mH is connected to an a.c. supply with frequency f. If the reactance of the inductor isΩ, what is the value of f?
1.45 ×103 \times10^3\ ×103 Hz
3.00 \times10^3\×103 Hz
4.77 \times10^3\×103 Hz
7.16 \times10^3\×103 Hz
Q.3
The highest value reached by the voltage or current in one cycle is called:
Instantaneous value
Peak to peak value
Peak value
Root mean square value
Q.4
What is alternating current
the process of inducing an emf (voltage) with a change in magnetic flux
Electric currents whose direction and magnitude change periodically depending on time are called alternating current
Steady current which delivers the same average power as the a.c. to a resistive load.
Making a rectified current more steady (or smooth) by placing a capacitor in parallel with the resistor
Q.5
The electricity in our house is
AC
DC
BC
AD
Q.6
An electric current that continually reverses direction over time is known as a(n)
direct current
alternating current
simple current
Q.7
Which of the following general equations represent AC current
I=Iosin(2πft)I=I_o\sin\left(2\pi ft\right)I=Iosin(2πft)
I=Iosin(2πft)I=I_o\sin\left(\frac{2\pi}{f}t\right)I=Iosin(f2πt)
I=Iocos(ωt)I=I_o\cos\left(\omega t\right)I=Iocos(ωt)
I=Iocos(t)I=I_o\cos\left(t\right)I=Iocos(t)
Q.8
Which is the correct equation of VrmsV_{rms}Vrms ?
Vrms=VoV_{rms}=V_oVrms=Vo
Vrms=2VoV_{rms}=\frac{\sqrt{2}}{V_o}Vrms=Vo2
Vrms=Vo2V_{rms}=\frac{V_o}{\sqrt{2}}Vrms=2Vo
Vrms=Vo2sin 2tV_{rms}=\frac{V_o}{\sqrt{2}}\sin\ 2tVrms=2Vosin 2t
Q.9
Rms value of ac current is the equivalent direct current which produces
the same average energy
the same power dissipation
the same rate of current flow
the same rate of power use
Q.10
A pure resistor is connected to an a.c. source where its current is given by I=5.0 sin 628t. Which of the following statements is not true about the circuit?
The peak value of current flowing through the resistor is 5.0 A
The root mean square current flowing through the resistor is 3.5 A
The frequency of the current flowing through across the resistor is 120 Hz
The equivalent direct current which gives the same average heating power in the resistor is 3.5 A
Q.11
A power supply has a peak value ofVolts sine wave, what is the effective dc voltage of this power supply?
306 V
433 V
612 V
220 V
Q.12
A heater is rated asV,kW. The valueV refers to
average voltage
r.m.s voltage
peak voltage
Q.13
The average current/ voltage value will not be zero only if it is
step up
rectified
amplified
intensified
Q.14
High potential voltage produced by three-phase generators commonly used in
filament
X-ray tube
transformer
anode
Q.15
The combination of resistance, capacitance and induntance is referred to
impedance
reactance
angular frequency
amplitude
Q.16
Voltage leads the current in an AC generators can be referred to
resistance
capacitance
inductance
Q.17
The resistor in an AC will cause
no phase difference
V lead I
I lead V
I lags V
Q.18
The effective voltage value is
25%
50%
71%
90%
Q.19
The distance of the waveform travel in one cycle is referred to
amplitude
wavelength
time
frequency
Q.20
In AC generator, maximum emf generated at an angle of
0 and 90
90 and 180
90 and 270
180 and 360
Q.21
AC generators works based on
Faraday's Law
Lenz Law
Newton's Law
electrostatic law
Q.22
AC generators used to produce alternating current by converting
kinetic energy into potential energy
potential energy into electrical energy
kinetic energy into electrical energy
electrical energy into kinetic energy
Q.23
The maximum instantaneous value measured from zero value is known as?
Peak value
Peak to peak value
Cycle
Period
Q.24
The repetition of a variable quantity, recurring at equal intervals, is known as ___________
Waveform
Instantaneous value
Cycle
Period
Q.25
The variation of a quantity such as voltage or current shown on a graph is known as ___________
Waveform
Peak value
Instantaneous value
Period
Q.26
Alternating voltage (V) is represented by the equation
V(t) = Vm eωt
V(t) = Vm sin ωt
V(t) = Vm cot ωt
V(t) = Vm tan ωt
Q.27
The unit of frequency is
Cycle
Cycle-second
Hertz/second
hertz
Q.28
A vector quantity has
Only magnitude
Only direction
Both (a) and (b)
none of these
0 h : 0 m : 1 s
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