MSBTE I Scheme Practice MCQs of “Element
of Electrical Engineering (22215)”
UNIT-2. AC Fundamentals.
1. The power consumed in
a circuit element will be least when the phase difference between the current
and voltage is
(A) 180°
(B) 90°
(C) 60°
(D) 0°
2. Form Factor is the
ratio of
(A) Average value/r.m.s.
value
(B) Average value/peak
value
(C) r.m.s. value/average
value
(D) r.m.s. value/peak
value
3. Capacitive reactance
is more when
(A) Capacitance is less
and frequency of supply is less
(B) Capacitance is less
and frequency of supply is more
(C) Capacitance is more
and frequency of supply is less
(D) Capacitance is more
and frequency of supply is more
4. Pure inductive circuit
(A) Consumes some power
on average
(B) Does not take power
at all from a line
(C) Takes power from the line
during some part of the cycle and then returns back to it during other part of
the cycle
(D) None of the above
5. Power factor of the
following circuit will be zero
(A) Resistance
(B) Inductance
(C) Capacitance
(D) Both (B) and (C)
6. The double energy transient
occur in the
(A) Purely inductive
circuit
(B) R-L circuit
(C) R-C circuit
(D) R-L-C circuit
7. In any A.C. circuit
always
(A) Apparent power is
more than actual power
(B) Reactive power is
more than apparent power
(C) Actual power is more
than reactive power
(D) Reactive power is
more than actual power
8. Magnitude of current
at resonance in R-L-C circuit
(A) Depends upon the
magnitude of R
(B) Depends upon the
magnitude of L
(C) Depends upon the
magnitude of C
(D) Depends upon the
magnitude of R, Land C
9. The safest value of
current the human body can carry for more than 3 second is
(A) 4 mA
(B) 9 mA
(C) 15 mA
(D) 25 mA
10. The purpose of a
parallel circuit resonance is to magnify
(A) Current
(B) Voltage
(C) Power
(D) Frequency
Part-2
1. The power is measured in terms of decibels in case of
(A) Electronic equipment
(B) Transformers
(C) Current transformers
(D) Auto transformers
2. Wire-wound resistors are unsuitable for use at high frequencies
because they
(A) Create more electrical noise
(B) Are likely to melt under excessive eddy current heat
(C) Consume more power
(D) Exhibit unwanted inductive and capacitive effects
3. The product of apparent power and cosine of the phase angle between
circuit voltage and current is
(A) True power
(B) Reactive power
(C) Volt-amperes
(D) Instantaneous power
4. In a series resonant circuit, the impedance of the circuit is
(A) Minimum
(B) Maximum
(C) Zero
(D) None of the above
5. In series resonant circuit, increasing inductance to its twice value
and reducing capacitance to its half value
(A) Will change the maximum value of current at resonance
(B) Will change the resonance frequency
(C) Will change the impedance at resonance frequency
(D) Will increase the selectivity of the circuit
6. In a loss-free R-L-C circuit the transient current is
(A) Oscillating
(B) Square wave
(C) Sinusoidal
(D) Non-oscillating
7. In a circuit containing R, L and C, power loss can take place in
(A) C only
(B) L only
(C) R only
(D) All above
8. Time constant of a capacitive circuit
(A) Increases with the decrease of capacitance and decrease of resistance
(B) Increases with the decrease of capacitance and increase of
resistance
(C) Increases with the increase of capacitance and decrease of resistance
(D) Increase with increase of capacitance and increase of resistance
9. The effective resistance of an iron-cored choke working on ordinary
supply frequency is more than its true resistance because of
(A) Iron loss in core
(B) Skin effect
(C) Increase in temperature
(D) Capacitive effect between adjacent coil turns
10. Skin effect occurs when a conductor carries current at _________
frequencies.
(A) Very low
(B) Low
(C) Medium
(D) High
Part-3
1. Which of the following
refers to a parallel circuit?
(A) The current through
each element is same
(B) The voltage across
element is in proportion to it's resistance value
(C) The equivalent
resistance is greater than any one of the resistors
(D) The current through
any one element is less than the source current
2. The frequency of
domestic power supply in India is
(A) 200 Hz
(B) 100 Hz
(C) 60 Hz
(D) 50 Hz
3. The frequency of an
alternating current is
(A) The speed with which
the alternator runs
(B) The number of cycles
generated in one minute
(C) The number of waves
passing through a point in one second
(D) The number of
electrons passing through a point in one second
4. In a pure inductive
circuit if the supply frequency is reduced to 1/2, the current will
(A) Be reduced by half
(B) Be doubled
(C) Be four times as high
(D) Be reduced to one
fourth
5. A sine wave has a
frequency of 50 Hz. Its angular frequency is _______ radian/second.
(A) 100 n
(B) 50 jt
(C) 25 JT
(D) 5 n
6. Two waves of the same
frequency have opposite phase when the phase angle between them is
(A) 360°
(B) 180°
(C) 90°
(D) 0°
7. In a pure inductive
circuit
(A) The current is in
phase with the voltage
(B) The current lags
behind the voltage by 90°
(C) The current leads the
voltage by 90°
(D) The current can lead
or lag by 90°
8. The time constant of a
series R-C circuit is given by
(A) R/C
(B) RC2
(C) RC
(D) R2C
9. A heater is rated as
230 V, 10 kW, A.C. The value 230 V refers to
(A) Average voltage
(B) r.m.s. voltage
(C) Peak voltage
(D) None of the above
10. Apaporis
(A) A line which
represents the magnitude and phase of an alternating quantity
(B) A line representing
the magnitude and direction of an alternating quantity
(C) A colored tag or band
for distinction between different phases of a 3-phase supply
(D) An instrument used for
measuring phases of an unbalanced 3-phase load
Part-4
1. The series and
parallel resonance on L-C circuit' differs in that
(A) Series resistance
needs a low-resistance source for sharp rise in current
(B) Series resonance
needs a high-resistance source for sharp increase in current
(C) Parallel resonance
needs a low-resistance source for a sharp increase in impedance
(D) Parallel resonance
needs a low-resistance source for a sharp rise in line current
2. In each of the three
coils of a three phase generator, an alternating voltage having an r.m.s. value
of 220 V is induced. Which of the following values is indicated by the
voltmeters?
(A) 220 V
(B) 220 √3 V
(C) 220/√3 V
(D) None of the above
3. In a highly capacitive
circuit the
(A) Apparent power is
equal to the actual power
(B) Reactive power is
more than the apparent power
(C) Reactive power is
more than the actual power
(D) Actual power is more
than its reactive power
4. The power factor at
resonance in R-L-C parallel circuit is
(A) Zero
(B) 0.08 lagging
(C) 0.8 leading
(D) Unity
5. In a R-L-C circuit
(A) Power is consumed in
resistance and is equal to IR
(B) Exchange of power
takes place between inductor and supply line
(C) Exchange of power
takes place between capacitor and supply line
(D) All above are correct
6. In an AC. circuit, a
low value of kVAR compared with kW indicates
(A) Low efficiency
(B) High power factor
(C) Unity power factor
(D) Maximum load current
7. Which of the following
statements pertains to resistors only?
(A) Can dissipate
considerable amount of power
(B) Can act as energy
storage devices
(C) Connecting them in
parallel increases the total value
(D) Oppose sudden changes
in voltage
8. The power factor of a
D.C. circuit is always
(A) Less than unity
(B) Unity
(C) Greater than unity
(D) Zero
9. The form factor is the
ratio of
(A) Peak value to r.m.s.
value
(B) r.m.s. value to
average value
(C) Average value to
r.m.s. value
(D) None of the above
10. Pure inductive
circuit takes power from the A.C. line when
(A) Applied voltage
decreases but current increases
(B) Applied voltage
increases but current decreases
(C) Both applied voltage
and current increase
(D) Both applied voltage
and current decrease