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WorksheetsEEJ123
Total questions: 100
Worksheet time: 50mins
As a loop of wire with a resistance of 10 ohms moves in a constant non-uniform magnetic field, it loses kinetic energy at a uniform rate of 4.0 mj/a. The induced current in the loop
10mA
30mA
20mA
cannot be calculated from the given data
Two resistors are connected in parallel across a potential difference. The resistance of resistor A is twice that of resistor B. If the current carried by resistor A is I, Then what is the current carried by B?
4I
2I
I
I/2
Current has units of
Coulomb
ohm
volt
coulomb/second
Calculate the power required to raised a 639 kg mass, 20.74m in 2.120 minutes.
1.430 kW
1.022kW
1.340kW
1.220kW
A parallel plate capacitor with plates of area A that are separated a distance d by air is initially charged with charge q. The energy stored in the capacitor initially is E. The plates are then separated by 2d. What is the new energy stored in the cpacitor?
1/2 E
0
2E
E
A 15 ohm resistor is connected in parallel with a series combination of resistors of 8 and 12 ohms. If the voltage drop across the 8 ohms resistor is 48V, what is the total current in A?
16
18
20
22
Two 110V light bulbs, one 25 and the other 100W, are connected in series to a 110V source. Then, which of the following statement is correct with regard to above sentence?
None of these
the current in the 100W bulb is less than that in the 25W bulb
Each bulb will have a potential difference of 55V.
both bulbs will light with equal brightness
Compared to Gauss-Seidel, Newton-Raphson method takes
Less number iteratios and more time per iteration
Less number iteratios and less time per iteration
More number iteratios and more time per iteration
More number iteratios and less time per iteration
The value of inductance per conductor in three phase line is__times the loop inductance for single phase lines
1/3
1/2
2
1
Which of the following cannot have a single unit of 100 MW
Hydro power plant
Steam power plant
Diesel power plant
Nuclear power plant
Heating effect of current has an undesirable side effect in
electric oven
immersion heater
electric iron
vacuum cleaner
In an oscillating LC circuit, the total stored energy is U. The maximum energy stored in the capacitor during one cycle is
U/2
U
U/2pie
u/pie
What is the allowable rating for branch overload protection if fuse is used for a hermetic motor compressor with rated load current of 27 A?
30A
25A
35A
20A
Determine the circuit element and its value for V = 120 sin (377t - 30degree) volts and I=4sin (377t + 60degree) amps
XC = 30 ohm and C = 66.31 microF
XC = 30 ohm and C = 88.42 microF
XC = 40 ohm and C = 66.31 microF
XC = 40 ohm and C = 88.42 microF
Which is not a standard distribution voltage in the Philippines?
13.2 kV
13.8 kV
34.5 kV
69 kV
Which of the following is a variable renewable source of energy (VRE)?
Gas turbine plant
Solar plant
Coal plant
Diesel plant
The reactance in ohms of a 35IF capacitor connected to a 400Hz generator is
0.088
11
0.014
0
A series RL circuit is connected across a 120V, 60Hz source and draws a current of 0.5 A of 0.7 lagging pf. Determine the values of R and L
171 ohm, 0.455 H
168 ohm, 0.544 H
171 ohm, 0.544 H
168 ohm, 0.455 H
In a transmission line of negligible resistance, the surge impedance will be
square root of LC
square root of L/C
square root of 1/LC
square root of C/L
A 30 mile, three phase transmission line is to deliver 20,000kW at 69kV at 85% power factor. The line resistance is 0.324 phm per mile and inductive reactance is 0.737 ohm per mile. What is the line loss?
1,050 kW
376.7 kW
997 kW
1,130.3 kW
The effect of series capacitor on a transmission line is to improve
steady state stability
transient stability
A and B both
none of these
One conductor of a three phase line is open. The current flowing to the delta- connected load through line a is 20A. With the current in line a as reference and assuming that line c is open, What is the negative sequence current of phase a?
10 + j5.78
10 - j5.78
j11.55
-10 + j5.78
What is the actual voltage of the high leg (middle) for the three phase, four wire delta grounded system 240/120V secondary voltage?
170V
208V
138V
199V
The readings of the wattmeter will be same in the two wattmeter method when
load in one phases is zero
power factor is unity
power is 0.50
neutral is grounded
A telegraph circuit consists of a 300ohm relay in series with fime wires having a resistance of 25ohms. If it takes 72mA to operate the relay, What voltage in V must be impressed ata the sending end of the circuits?
19.8
30.6
23.4
27.1
In a purely resistive ac circuit, the current
lags behind the emf in phase
leads the emf in phase
is in phase with the emf
leads the emf in half the cycle and lags behind it
The magnetic torque exerted on a flat current-carrying loop of wire by a uniform magnetic field B is
maximum when the plane of the loop is perpendicular to B
independent of the orientation of the loop
maximum when the plane of the loop is parallel to B
dependent on the shape of the loop for a fixed loop area
Differential relays are used to protect the transformer against
Reverse current
Internal faults
Overcurrent
No voltage
A disconnecting means shall be located within sight from the motor controller.
manufacturing rule
construction rule
wiring design rule
installation rule
Only one of the two devices on a link can transmit the other can only receive.
Half duplex
Full duplex
Simplex
Bicomm
Diode exhibits variable capacitance that depends on the reverse voltage.
Gunn
Varactor
Hot carrier
Impatt
The rating of a circuit breaker is generally determined on the basis of__
Line to line fault current
Symmetrical fault current
Single line to ground fault current
Double line to ground fault current
In two-wattmeter method of power measurement, the reading of the two wattmeters were 6717 watts and 2658 watts, respectively. Find the power factor.
0.90
0.70
0.60
0.80
What contains in each cell site of cellular telephone system?
Repeater
Control computer
Direct-link to a branch exchange
Touch-tone processor
A single loop of wire with a radius of 7.5 cm rotates about a diameter in a uniform magnetic field of 1.6 T. To produce a maximum emf of 1.0 V, it should rotate at:
0
2.7 rad/s
5.6 rad/s
35 rad/s
For remote operation, which of the following a circuit breaker must be equipped with?
Inverse time
Time delay
Very inverse time
Shunt
Which of the following protects a cable against mechanical injury during handling and laying?
Armouring
Bending
both
either
You are facing a loop of wire which carries a clockwise current of 3.0A and which surrounds an area of 5.8 x 10-2 m2. The magnetic dipole moment of the loop is:
3.0A m2, away from you
3.0A m2, toward you
0.17A m2, away from you
0.17A m2, toward you
If R is the distance from a magnetic dipole, then the magnetic field it produces is propotional to:
R
1/R
R^2
1/R^3
An LC circuit has a capacitance of 30microF and an inductance of 15mH. At time t=0 the charge on the capacitor is 10microC and the current is 20mA. The maximum charge on the capacitor is:
8.9microC
10microC
12microC
17microC
At time t=0 the charge on the 50microF capacitor in an LC circuit is 15microC and there is no current. If the inductance is 20mH the maximum current is:
15nA
15microA
6.7mA
15mA
If an appliance has a motor load of 12A and a heating load of 15A, What is the required ampacity of the branch circuit conductors?
35A
25A
20A
30A
Two inductance of L1=5H and l2=4H are connected in series. What is the total inductance when mutual inductance is zero?
1H
9H
2.2H
18H
A 4,400 V, 60Hz transformer has core loss of 840 watts, of which one-third is eddy current loss. What is the core loss when the transformer is connected to a 4,600v, 60 HZ source?
926 W
907W
873W
944W
A certain capacitor, in series with a resistor, is being charged. At the end of 10 ms its change is half the final value. What is the time constant on this process in ms?
2.3
10
6.9
14
A rice mill will be served by two- 50 KVA transformers, 7.620KV/240V. The transformers will be installed as open -delta bank to serve the three-phase load of the rice mill. What is the maximum KVA load that this bank can carry without overloading?
50
100
86.6
75.5
A motor is supplying 60 N-m of torque to its load. If the motor's shaft is turning at 1800rpm, what is mechanical power to the load in horsepower?
9.2
11.4
7.6
15.2
What is the equivalent of 1 + a + a^2?
0
1
1+3
-1
A 3H inductor has 2000 turns. How many turns must be added to increase the inductance to 5H?
825 turns
582 turns
2582 turns
2825 turns
A car battery is rated at 80 ampere-hour, An ampere-hour is a unit of
Power
energy
charge
current
Four 20 ohm resistors are connected in series and the combination is connected to a 20V emf device. The potentional difference across any one of the resistors is:
1V
4V
5V
20V
Faradays law states that an induced emf is proportional to:
the rate of change of the magnetic field
the rate of change of the electric field
the rate of change of the magnetic flux
the rate of change of the magnetic flux
Four 20 ohm resistors are connected in parallel and the combination is conneted to a 20V emf device. The current in the device is:
0.25
1
v
5
A current is clockwise around the outside edge of this page and a uniform magnetic field is directed parallel to the page, from left to right. If the magnetic force is the only force acting on the page, the page will turn so the right edge:
moves toward you
moves away from you
moves to your right
moves to your left
Three single phase transformers rated 25 kva each are connected in delta-delta to supply a balanced load of 75kVA. One transformer is removed for repair, What is the kVA of each remaining transformer?
43.3
50
57.7
34.3
Three capacitance 4microF, 5microF and 6microF are connected in series across a 110-volt supply. Find the total value of charge passing through each capacitor.
89microC
178micro C
267 micro C
445 micro C
A charged capacitor and an inductor are connected in series. At time t=0 the current is zero but the capacitor is charged. If T is the period of the resulting oscillations, the next time after t=0 that the charge on the capacitor is a maximum is:
T/2
T
T/4
2T
A small wind generator is designed to generate 75kW of power at a wind velocity of 30mi/hr. What is the approximate blade diameter of the wind generator in ft?
35.4
31.9
33.6
37.3
Which of the following protective device operates on the principle of Kirchhoff's a Current Law?
Instantaneous Overcurrent Relay
Differential Protective Relay
Undercurrent Relay
AC time Overcurrent Relay
The value of inductance per conductor in three phase line is ___times the loop inductance for single phase lines.
1/3
1/2
2
1
Four wires meet at a junction. The first carries 4A into the junction, the second carries 5A out of the junction, and the third carries 2A out of the junction. The fourth carries:
7A out of the junction
3A out of the junction
7A into of the junction
3A into of the junction
In a single-phase transformer, the core losses is 60W at 40Hz and 95W at 60Hz both measured at the same maximum value of flux density. Find the core losses in W at a frequency of 50 Hz.
69
77
89
56
The nameplate speed of a 60Hz, 3-phase induction motor is 1,175rpm. what is its number of poles?
2
4
6
8
The per phase line loss in a 40km long transmission line is Not to exceed 60 kW while it is delivering 100A per phase. If the resistivity of the conductor material is 1.72 x 10^8 ohmmeter, determine the required conductor diameter.
1.2071 cm
1.1721 cm
1.2083 cm
1.2204 cm
The voltage regulation is MORE consider in the design of
a motor
a generator
the feeder
the transmission line
A 115 kv three phase transposed transmission line is composed of 2 ACSR 336,000 cml, 30/7 Oriola conductors per phase with horizontal configuration: D12=7ft, D23=7ft, D13= 14ft. The line spacing is measured from the center of the bundied conductors. The distance between the conductors of the bundle is 6 inches. The conductors of the bundle is 6 inches. The conductors have a diameter of 0.741 inch and a GMR of 0.02255ft. Find the capacitance per phase for 20km of the line in microfarads.
0.1300
0.2719
0.2889
0.2609
Which of the following type of fault used only the equivalent positive sequence impedance of the circuit in the short circuit calculation?
Double line to ground
Three phase
Line to line
Line to ground
An unconventional conductor consists of three strands arranged vertically. Find the GMR in terms of radius r of and individual strand
1.564r
1.764r
1.704r
1.864r
The terminal voltage of a battery is 11.8V when delivering 20W of power to an external load resistor R. If the battery has an emf of 15V, find the internal resistance of the battery.
1.96 ohm
1.89 ohm
1.68 ohm
1.75 ohm
A stationary conducting loop with internal resistance of 0.50 ohm is placed in a time varying magnetic field. When the loop closed, a current of 5A flows through it. What will the current be if the loop is opened to create a small gap and a 2 ohm resistor is connected across its open ends?
2A
1A
4A
3A
A uniform magnetic field makes an angle of 30 degree with the x-axis. If the magnetic flux through a 1m2 portion of the xy plane is 5 Wb then the magnetic flux through a 2-m2 of the same plane is Wb
10
8
4
5
A coil of wire having a resistance of 3.75 ohm and carrying a current of 0.3A is in parallel with an unknown resistance through which there a current of 1.5A. Dtermine the total equivalent resistance.
0.625ohm
0.865ohm
0.489ohm
0.549ohm
A 3 phase motor is rated for 50A. What is the minimum inverse time delay circuit breaker rating
75A
100A
250A
125A
A 30cd standard light source is compared with a lamp of unknown intensity using a greass-spot photometer. The two light sources are placed 1m apart, and the grease spot is moved toward the standard light. When the grease spot is 25cm from the standard light source, the illumination is equal on both sides, Where should the grease spot be placed for the illumination by the unknown light source to be exactly twice the illumination of the standard source?
32cm from standard
68cm from standard
18cm from standard
82cm from standard
A 120V, 200A single phase is supplied by a source 1000ft. away through a copper conductor with a diameter of 0.45in, and resistivity of 0.4 ohm-cm/ft. What voltage must the supply be?
150.64V
124.05V
140.50V
118.45V
Copper loss of a transformer are determined by means of a an___test.
open circuit
polarity
short circuit
inductive circuit
Macro-sequence current will flow in a transmission line there is
a fault across all three phases
an overvoltage in the line due to switching
a line to line fault
double line to ground fault
A transmission line cable consists of 26 strands of identical copper conductor, each 1.255mm in diameter. The length of the cable is 10km but, because of the twist of the strands, the actual ohmmeter, what is the resistance of the cable?
1.08 ohm
5.66 ohm
5.39 ohm
1.13 ohm
The trip coil of a circuit breaker is connected through a CT of ratio 50:1. iF THE NORMAL LINE CURRENT IS 160A and circuit breaker is to operate at 125% normal, the trip mechanism should be set operate at trip current of ___A.
6
3.2
4
4.8
A 4157-V rms, three-phase suppy is applied to a balanced Wye- connected three-phase load consisting of three identical impedance of 38.4+j28.8 ohms. Taking the phase to neutral voltage Van as reference. What is the phasor current for phase B in Ampere
45.98+j19.64
-45.98+j19.64
45.98-j19.64
-45.98-j19.64
When the service consists of a multiple of individual disconnecting means for grounded system, the main bonding jumoer is required tobe located in ____disconnecting means
the first
each
the last
the largest
The power transmission capacity of the transmission is
A inversely proportional to the voltage
directly propotional to the voltage
porportional to the square of the voltage
proportional to the cube of the voltage
What is the equivalent IEEE device number for an under-volatage relay?
67
52
27
51
Modern locomotives are powered by DC motors driven by DC generators. Those are, in turn, driven by diesel engine. Which of the following is the reason for using such a configuration instead of AC generators-motor sets?
The DC equipment is significantly less expensive.
The DC configuration provides high torque and good incremental power at low speeds, and performs equally well at high speeds
Historically, the DC engines configuration has been used. There is no reason to change this.
By using the DC equipment, the power factor problems associated with AC equipment are avoided
An LC series circuit with an inductance L and a capacitor C has an oscillation frequency of f. Two inductors, each with inductance L, and two capacitors, each with capacitance C, are all wired in series and the circuit is completed. The oscillation frequency is
f/4
f
2f
f/2
One primary and one secondary terminal of a two winding transformer are connected to an ohmmeter instrument. What will be the reading on this instrument?
Infinity
Zero or Infinity
Equal to winding resistance
Zero
Which of the following statement is false?
RTOS performs tasks in predictable amount of time
Windows 98 is RTOS
Interrupts are used to develop RTOS
Kernel is the one of component of any OS
In a series circuit, the current is
inversely propotional to the resistance
variable
proportional to the resistance
constat
Certain voltmeter has an internal resistance of 10k-0 and a range from 0 to100V. To give it a range from 0 to 1000v, one should connect
100k-o in series
100k-o in parallel
90k-o in parallel
90k-o in series
Which of the following will you connect to make a galvanometer into an ammeter?
a high resistance in parallel
a high resistance in series
a low resistance in series
a low resistance in parallel
Two equal charger of opposite signs are separeted by a horizontal distance of 70mm. If the resultant electric field at the midpoint of the line is 4 x 104 N/C. What is the magnitude of each charge?
3.6nC
2.7nC
4.5nC
2.4nC
The illumination of a surface 3.40m directly below a light source is 25 lux. Find the intensity of the light source.
347 cd
289cd
231cd
393cd
A 120V power line is protected by a 15A fuse . What is the maximum number of 120V, 500W light bulbs that can be operated at full brightness from this line?
2
3
4
5
The boundary of the protection system is determined by the location of
voltage transformers
current transformers
Protective relays
circuit breakers
A piece of conductor 10 cm long moves across a magnetic field of 10k gauss at a velocity of 120 cm/sec. What is the voltage across the conductor?
12mV
1.20mV
120mV
0.12mV
An ACSR conductor has (n-1) layers around its single center strand, the total number of strands will be
3n^2 + 3n + 1
3n^2 - 3n - 1
3n^2 + 3n - 1
3n^2 - 3n + 1
Approximately how far away must an isolated positive point charge of 1 x 10^(-8) C be in order for it to produce an electric potential of 100V? The charge is in free space with e=8.85 x 10^(-12) C^2/N*m^2.
8.6m
0.90m
1.2m
5.3m
A 69kV three-phase transposed line is composed of one ACSR 336,400 cmil, 26/7 Linnet conductor per phase with a horizontal configuration of D12=5ft, D23=5ft, and D13=10ft. The conductors have a diameter of 0.721 inch and a GMR of 0.0243ft. Find the inductance per phase per kilometer of the line.
1.0963 mH/km
1.1116 mH/km
1.1505mH/km
1.1233 mH/km
In a 12V battery supplies 10A, find the amount of energy in kJ delivered in 1 HOUR.
120
216
324
432
Three resistors A, B, and C are connected in series to a 120V supply. If the resistor A=60 ohms and the voltage across resistor B= 40V when the current is 1/2A, What is the resistance of resistor C in ohm/s?
105
90
100
110
