WorksheetsEE 9
Total questions: 49
Worksheet time: 25mins
The boundary of the protection system is determined by the location of ___.
protective relays
circuit breakers
current transformers
voltage transformers
How much larger is the rotor reactance of a SCIM at start-up than it is when the motor operates at 5 percent slip?
5 times
25 times
20 times
10 times
Which of the following is the electrical device that is usually required to be installed in moisture area in the dwelling unit in order to protect the person from electric shock?
Power Fuse
Circuit breaker
Arc-Fault Circuit Interrupter
Ground-Fault Circuit Interrupter
Power factor of synchronous motor can be made leading by adjusting its:
Supply voltage
Excitation
Speed
Supply frequency
The effective resistance of conductor is increased by ___.
Both skin effect and proximity effect
proximity effect
corona effect
skin effect
For two alternators operating in parallel, if the load shared by one of the alternators is to be increased, the field excitation is ___.
to be kept constant but input torque should be decreased
to be kept constant but input torque should be increased
to be strengthened keeping input torque the same
to be weakened keeping input torque the same
In positive voltage sequence, which statement is true?
V_LL is in phase with V_PH
V_LL leads V_PH by 30°
V_LL lags V_PH by 60°
V_LL lags V_PH by 30°
What is the reason why thermal powerplant decrease capacity during summer?
Temperature rise of the lake
Decrease water level at the lake
All of the choices
Many people go swimming on lake
Increasing the voltage of the transmission system to double its original value with the same power to be transmitted, the new power losses of the transmission system will be ___ of the original value.
one-fourth
one half
the same
twice
Motors must be labeled with the following nameplate rating, manufacturer's name and etc. This is the:
Wiring Design Rule
Construction Rule
Installation Rule
Manufacturing Rule
Which of the following is NOT part of your unbundling rate in your Meralco electric bill?
Generation
Distribution
Supplier
Transmission
If the current in a circuit doubles, the heat produced in a conductor increases by a factor of ___.
16
2
4
9
When the amplitude of the oscillator in a series RLC circuit is doubled, the ___.
impedance is doubled
the voltage across the capacitor is halved
current amplitude is doubled
capacitor reactance is halved
Which of the following statement is CORRECT for Faraday's law?
An induced electromotive force is proportional to the rate of change of magnetic field.
An induced electromotive force is proportional to the rate of change of electric flux.
An induced electromotive force is proportional to the rate od change of electric field.
An induced electromotive force is proportional to the rate of change of magnetic flux.
In a SCR circuit, the angle of conduction can be changed by changing:
Forward current rating
Gate voltage
Anode voltage
Anode current
The breakdown mechanism in a lightly doped p-n junction under reverse biased condition is called:
High voltage breakdown
Avalanche breakdown
Zener breakdown
Breakdown by tunnelling
Which of the following has the greatest effect in decreasing the oscillation frequency of an LC circuit? Using instead ___.
L/2 and 2C
2L and 2C
2L and C/2
L/2 and C/2
Why can't a three-phase synchronous motor start by itself?
It has no starting torque
Rotor is not magnetized
Rotor resistance is too low
It operates at zero slip
Conductors ___ and larger shall be stranded when installed in raceways.
8.0mm²
30mm²
3.5mm²
5.5mm²
Four wires meet at a junction. The first carries 4 A into the junction, the second carries 5 A out of the junction and the third carries 2 A out of the junction. The fourth carries ___ the junction.
7 A into
7 A out
3 A out
3 A into
Name the effect which resulted because of the size of conductor, frequency, and the specific resistance of conducting material.
Corona effect
Proximity effect
Skin effect
Thompson effect
The skin effect in conductors is due to non-distribution of current in it and major portion of the current is near the ___.
Surface
radial lines
center
axis
A capacitance C is charged through R. The time constant of the charging circuit is given by:
R/C
RC
1/RC
C/R
Which of the following statements is FALSE?
Interrupts are used to develop RTOS.
RTOS performs tasks in predictable amount of time.
Windows 98 is RTOS.
Kernel is the one component of any OS.
Receptacle outlet shall be located not more than ___ above countertop.
300
250
500
600
Which of the following refers to the power loss due to alternating magnetization and demagnetization of the core material?
Eddy current loss
Copper loss
No-load loss
Hysteresis loss
The effect of the dielectric is to:
Increase the working voltage
Decrease the capacitance
Reduce the working voltage
Increase the capacitance
Guy wire is used in the construction of distribution lines for what purpose?
Protection against surges
Providing emergency grounding
Supporting the pole
The apparent power drawn by a balanced three-phase consumer for line voltage V and line current I is given by:
Sqrt 3 VI
Sqrt 3 VI cosθ
3 VI cosθ
VI
What is the primary function of the tubes welded on the side of oil-type transformer?
For voltage regulation improvement.
To improve the cooling.
For transformer losses reduction.
To increase its efficiency.
The current flowing in L and C at parallel resonant are:
Equal
Different
Zero
Infinite
The purpose of a grid system is to:
make distribution of energy at reasonable cost
supply energy to remote areas
interconnect the power stations
make extra high voltage available to consumers
An alternator running in parallel with the other alternators all having automatic voltage regulators is to be taken off the bus. The usual procedure before opening the switch is to ___.
reduce the power fed to the prime mover
do nothing
increase alternator excitation
reduce alternator excitation
In a DC transmission line:
It is necessary for the sending end and receiving end to be operated in synchronism.
The effect of inductive and capacitive reactance's are greater than in an AC transmission line of the same rating.
Power transfer capability is limited by stability considerations.
There are no effects due to inductive and capacitive reactance's.
The value of the resistor creating thermal noise is doubled. The noise power generated is therefore:
Unchanged
Double
Quadrupled
Halved
A permeable substance is one ___.
which is a good conductor
through which the magnetic lines of force can pass very easily
which can behave as a conductor as well as an insulator
which is a strong magnet
Which of the following statement is CORRECT concerning electric field?
Electric field lines may cross.
Electric fields are closed together where the field is large.
Electric field point away from a negatively charged particle.
A charged point particle released from the rest moves along a field line.
Positive charge is distributed uniformly throughout a non-conducting sphere. The highest electric potential occurs ___.
at the center
at the surface
far from the sphere
just outside the surface
DMC was created by the Energy Regulatory Commission to monitor the compliance of the distribution utilities to the PDC. DMC stands for ___.
Distribution Management Committee
Distribution Management Commission
Distribution Market Committee
Distribution Market Commission
A hermetic motor - compressor has 20 Amp full load current. What is the rating of the disconnecting means?
28.75 A
23 A
30 A
25 A
What does IEMOP stand for?
Independent Electricity Market Operator of the Philippines
Independent Energy Market Operator of the Philippines
Integrated Electricity Market Operator of the Philippines
Integrated Energy Market Operator of the Philippines
In practice, the three phase conductors of a three-phase line are seldom equilaterally spaced. The usual nonsymmetrical spacing produces unequal inductances in the three phases, leading to unequal voltage drops and imbalance in the line. To offset this imbalance, the positions of the conductors are interchanged at regular intervals in the line. This practice is known as ___.
I. transposition
II. interchange
I
II
Either I or II
Both I and II
If B-phase of a 3-phase wye connected alternator become reverse connected by mistake, it will not affect ___.
V_bc
V_cb
V_ca
V_ab
What is the rms value of an AC current?
The steady current that produces the same rate of heating in a resistor as the actual current.
That steady current that will charge a battery at the same rate of the actual current.
Its average value.
Its peak value.
AC system has the following disadvantages over DC system EXCEPT:
Proximity effect exists
Line regulation is more
Charging current exists
Skin effect exists
What does PEMC in EPIRA stand for?
Philippine Energy Market Corporation
Philippine Electricity Market Corporation
Philippine Electrical Marketing Corporation
Private Energy Marketing Company
The emf induced in a coil by the charging of current in the neighboring coils is known as ___ emf.
series
speed
mutually induced
self-induced
The speed of dc shunt motor can be controlled:
By inserting a resistor in series with armature circuit.
By changing the field resistance.
Any of the choices
By changing the terminal voltage applied to armature.
When transistors are used in series or parallel, a snubber circuit is used to:
Control the voltage
Limit di/dt
Control the current
None of the choices
