EE POWERLINE PREBOARD

3回閲覧 • 100問 • 1年前

問題一覧

In a certain country, the energy consumption is expected to double in 10 years. Calculate the percent growth rate.

6.93

A 120 volts de source is supplying three resistors in series. The first has 50 ohm resistance, second has 45 volts drop and third dissipates 25 watts power. What is the resistance R2?

90 ohms

Two capacitors C1= 6micro-farad and C2= 4micro-farad are connected in series. Find the equivalent capacitance in micro-farad

2.4

A 10-turn square coil of side 200mm is mounted on a cylinder 200mm in diameter. The cylinder rotates at a rate of 1800 rpm in a 1.1 tesla field. Determine the maximum value of the voltage induced in the coil

83 V

Which of the following equipment is used to limit short-circuit current level in substation?

Series reactor

Current limiting reactor are used to:

Bring down the fault level to minimum capacity

An overexcited synchronous motor is connected across a 100kVA inductive load having a 0.8 lagging power factor. The motor takes 10kW in power while idling(on no-load). Calculate the kVA rating of the motor if it is desired to bring the overall power factor to unity. The motor is not used to camy any load.

60.8 kVa

Which material has the least resistance

Copper/ Silver

Buchholz's relay is used in

Transformer protection

10. What is the total resistance of 11 resistors of 33 kilo-Ohms each when connected parallel?

3 kilo-Ohm

Which of the following is an instrument transformer

Potential transformers

For handling greater currents induction wattmeter's are used in conjunction with

Current Transformer

Which power plat has the least maintenance cost?

Hydroelectric PP

What is the type of relay that detect excessive current

Overcurrent Relay

Which of the following is are drawbacks of SF6 circuit breaker? I. Sealing problem of gas II. Presence of Moisture in the system is dangerous

I only

A magnet moves inside a coil. Which of the following factors can affect the induced ernf in the coil? I. the speed at which the magnet moves II. The magnet field of the magnet III The number of turns in the coil

I only

What is ANSI device number for AC Time overcurrent Relay?

A 125-Volt d-c generator whose internal resistance is 0.15 ohm is connected through a 0.45 ohm line resistor to charge two 90-volts storage batteries A and B respectively 0.32 ohm and 0.4 ohm, what are the charging currents?

25A & 20A

What is the moisture limit of transformer oil?

30-50 ppm

A shunt motor is running at 1200 rpm for a load which requires an armature current of 50 ampere from 230 volt source. At no load, the armature current is 5 amp. If the effect of armature reaction has reduced the air-gap flux by 2% from no load to full load, determine the no load speed. The armature resistance is 0.15 ohm.

1212 rpm

When the sole purpose of alternating current is to produce heat, the selection on value of the current

Root Mean Square

Calculate the reading which would be indicated by a hotwire ammeter in a circuit whose current is given by 10sinwt +3sin3wt + 2sin5wt amperes

7.5 A

What is the maximum number of bends permitted in rigid conduit?

4 quarter bends

Surge impedance of transmission line is given by

(L/C)^1/2

The permeability of material means

the conductivity of a material for magnetic lines of force

Appliance receptacle outlet installed in a dwelling unit for specific appliance, such as laundry equipment, shall be installed within ________ mm of the intended location of the appliance

1800

Two wattmeter both have reading 5kW when connected for two wattmeter method in a three phase 339.4 Volts circuit that has a balance delta load. Find the three phase impedance

69.1 cis 0 deg

Two inductance L1=5H and L2=4H are connected in series. What is the total inductance if the mutual inductance is zero

Two wattmeter method can be used to measure 3-phase power for

balanced and unbalanced load

What is the type of communication that only one of the two party can transmit at a time

Half duplex

A hermetic motor compressor has a rated load of 25A. What is the allowable ampere disconnecting means?

28.75 A

For constant transmission efficiency, the voltage is increased n times, the size of conductor will be

reduced to (1/n^2) times of the original

The line current in a 3-phase, 4 wire system are Ia=30+j40 amp; lb=20+j20 amp and Ic=-40-j20 amp respectively. What is the negative sequence current for phase A in amperes

25-j4

A 345kV transmission line has a series impedance of 4+j60 ohms and a shunt admittance of 12\times10^{-3} S. Using 100MVA and 345kV as base values, calculate the per unit admittance of the line

2.38

A 100-kVA, 60-Hz, 2200-V/220-V transformer is designed to operate at a maximum flux density of 1 T and an induced voltage of 15 volts per tum. Determine the cross-sectional area of the core?

0.0563 m^2

Which of the following protective relay/s operates in the principle of Kirchhoff's current law

Differential Relay

Which of the following will the effect of the electric shock in the human body depends on

Current flowing in the body

An electric motor takes 5A from a 220 volt line. Determine the energy in kWhr if the energy is supplied to the motor in 2hrs.

2.2

Protection used for personnel against electric shock is

GFCI

Given COP of 4 and QL of 20,000 kJ/hr, what is the approximate hp?

A tropical storm is going to the Philippine area of Responsibility (PAR), what alert is to be raised in accordance to the Philippine Distribution Code

Blue Alert

The direction of magnetic lines

from north pole to south pole

A common utilities tariff practice to penalize consumers whose power factor falls below __________ and give incentive for power factor above _______

85%, 85%

For which of the following parameter variation, the capacitance of the capacitor remain un affected

Thickness of the plate

A 30-cd standard light source is compared a lamp of unknown intensity using a grease spot photometer two light sources are placed im apart, and the grease spot moved toward the standard light. When the grease spot 25cm from the standard light source, the illumination is equal on both sides. Compute the unknown intensity of the unknown light.

270 cd

A certain amount of fuel contains 15 x 100 Btu of energy. What is the corresponding energy in kilocalories?

3.78 x 10^10 kCal

A circular top is located is 4m below and 3 m to the left of a lamp that emits 1800 lumens. What illumination is provided on the surface of the table?

4.58 lux

Power loss is important for the design of

Transmission line

Which is NOT a characteristic of an ideal transfomer?

finite permeability

The total cost of a diesel power plant per kW of installed capacity is less than that of steam power plant by

20 to 30%

Which of the following plants will take least time in starting from cold condition to full load operation

Hydroelectric power plant

Which of the following relays are used for phase fault on long time

Overcurrent relay/MHO relay

Which is not a consideration in surge arrester?

Insulation coordination

What is the unit of relative permeability?

it is dimension entity

If the torque angle d is continuously increases, system will become

unstable

In an oscillating LC circuit, the total stored energy is U and the maximum charge on the capacitor is Q. When the charge on the capacitor is Q/2, the energy stored in the inductor is:

3U/4

This mathlab command clears all data and variables stored in memory

Clear

A 150-g block on the end of a spring with a spring constant of 35 N/m is pulled aside 25 cm and released from rest. In the electrical analog the maximum charge on the capacitor is 0.25 C. The maximum current in the LC circuit is

0.38A

A 345kV transmission line has a series impedance of 4-100 ohms and a shunt admittance of 12\times10^{-1} S. Using 100MVA and 345kV as base values, calculate the per unit admittance of the line

2.38

A three phase load of 500KVA, 80% power factor lagging, it is desired to correct the power factor to 90% lagging by connecting overexcited motor that requires 120kW while driving mechanical load. What is the operating power factor of this motor?

0.85

Regarding Thevenin's equivalent, which of the following is not correct?

The Thevenin equivalent resistance is calculated when all voltage sources are open circuited

An RLC series circuit has L=100 mH and source and the C=1uF. It is connected to a 1000-Hz and source emf is found to lead the current by 75°. The value of R is.

126 Ω

Which of the following insulation colors identify the grounded conductor of a branch circuit?

White

Tall growing plants refer to plants, vines and other plant species, which grow or have the potential to grow more than _______ meter in height from the ground

three (3)

A three phase wye connected 20MW load of 0.866 pf lagging is to be supplied by a transmission line is 138kV. It is desired that the line losses not to exceed 5 percent of the load. If the per phase resistance of the line is 0.7 Ohm, what is the maximum length of the line?

The load consist of resistance R in parallel with a capacitor of reactance X. The load is fed from a single phase supply through a line of impedance 8.4+j11.2. The rms voltage is 1200 volts and the load is taking 30 kVA at 0.8 pf leading. Find the values of R

60 ohms

The load consist of resistance R in parallel with a capacitor of reactance X. The load is fed from a single phase supply through a line of impedance 8.4+i11. . The rms voltage is 1200 volts and the load is taking 30 kva at 0.8 pf leading. Find the values of X.

80 ohms

__________ is a way of sending multiple signal or stream of information over communications link over the same time in the form of single, complex signal

Multiplexing

* 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-ohm resistor is 48 V, what is the total current in A?

A 69 kV three phase transposed line is composed of one ACSR 336.4MCM, 26/7 Linnet conductor per phase with a horizontal configuration D12=D23==5It and D13=10ft. The conductors have a diameter of 0.721 inches and gmr of 0.0243ft. Find the inductance per phase per kilometer of the line.

1.1116 mH/km

Which of the following materials have very high permeablities?

ferromagnetic materials

Which is not a qualification for member of BEE?

at least 40 or 30 years old

Four 20 ohms resistors are connected in parallel and the combination is connected to a 20V emf device. The current in the device is

4.0A

Four 20 ohms resistors are connected in parallel and the combination is connected to a 20V emf device. The current in any one of the resistor is

1.0 A

The straight conductor of 100 cm long and carrying a current of 40 Amp perpendicular to the magnetic field 1.5 Wb/sq. mts. What is the mechanical power required in Watts to move the conductor a uniform speed of 5 m/sec?

300

A single phase motor runs a duty cycle: 20kW for 10s, 40 kW for 10s, 60 kW for 5s, 80 kW for 10s and idle for 10s. What must be the rating of the motor

47.6 kW

Given the following phase voltages Van =220V: zero sequence component of phase voltage Vbn=141+j168.5V; Vcn=-141+j168.5V. Find the

73.5+j112.3V

Given the following phase currents: Ia=3.5+j3.5 lbj3, and Ic=-2.6+j1.5 Determine the negative sequence current of phase A

0.313+j0.678

In a star connected system, the line current is

equal to the phase current

A 4 pole lap winding motor with 16 slots, 42 conductor per slot, 480 volt runs at 1800 rpm. Find the flux produced per pole

23.8 mWb

Which power plant cannot have single unit of 100 MW?

diesel power plant

A generator delivers a load through a pair of wires, each of which has a resistance of 0.06 ohm. If the load voltage and power are 120 v and 4.8 kW, respectively, what is the power loss in the line wires?

192 W

A motor is supplying 60 N-m of torque to its load. If the motor's shaft is turning at 1800rpm, what is the mechanical power to the load in horsepower?

15.2

The resistance of a copper wire at 30°C is 50 ohms. If the temperature coefficient of copper wire at 0°C is 0.00427, what is the resistance at 100°C

63.24 ohms

The heating value of coal largely depends on

Ash content

The speed of a 4-pole 60Hz synchronous machine will be

1800 r.p.m

The Floor area of office building is 600 sqm and has general lighting load of 28VA per sqm. How many 230V, 20A lighting load circuit of the building?

Which power plant has a minimum running/operating cost?

Hydro electric power plant

An instrument having current coil and a potential coil.

Wattmeter

What is IEEE device number for distance relay

Which of the following is not a distance Relay

Overcurrent relay

Which of the following is not a cause of noise in communication system?

Jeat agitation of electrical component

When one coil of magnetically coupled pair has a current of 5 amperes, the resulting flux 11=0.4 mWb and flux 12 =0.8 mWb resp. If the turns are N1=500 and N2=1500 Find L,

120 mH

Two coils having inductance L1=0.5H. L2=0.3H. At one instant, I1=12A and I2=5A Find the total energy stored when the coefficient of coupling is M=-0.45H.

12.75 J

Load of 12.5kVA 85% pf lagging is supplied from two machines. The first Machine has 7kW 80% pf. what is the real power of the other machine?

3.625 kW

Power Transformer connected wye-wye rated 100MVA 34.5KV/161kV has 10% reactance. What is the ohmic reactance referred at 34.5 KV7

1.19 ohm

Three resistors are connected in series across 240 volts de source draw 4 amperes. If V_{R1}=60 volts. R-1.5 R. What is R, in Ohms

Three resistors are connected in series across 240 volts de source draw 4 amperes. If V_{R1}=60 volts, R2=1.5R_{3}, What is R_{2} in Ohms

What does the cost per year for a power loss of the #10 AWG conductors that have a total resistance of 0.3 ohm with current flow of 24A. Cost of energy is $0.056 per kWh.

P84.8

100

Resistors A, B & C are connected in series. Resistor A is 60 ohms. Resistor B takes 40 volts when current is 0.5 ampere. Calculate the value of resistor C when supply voltage is 120 volts

100 ohms

DC CIRCUITS POWERLINE

premopremo remo · 75問 · 2年前

DC CIRCUITS POWERLINE