EE Lesson Objectives 2

Hazel Lynn Ramos · 95問 · 2年前

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what is the unit of relative permeability

unitless

what is used to prevent motorizing of a generator

reverse power relay

the DC armature winding in which the coil sides are place a full pitch apart is called ___ winding

full pitch = 180°

Which of the following limits the number of coils that may be placed on the armature of a DC motor or generator

coil to coil arcing due to the breakdown of insulation

Which of the following depends on the electromotive force of a dc generator

speed

what is the effects on current flow does in reversing the direction of movement of a conductor in the magnetic field of a generator

it reverses the direction of current flow

which of these is not a factor in determining the speed of a DC motor

the thickness of the commutator bars

Which DC motor cannot be used without a load connected to it

series

Which DC motor has high starting torque

series

in a DC motor, what is the definition of field resistance

it is the resistance of the excitation circuit

modern locomotives are powered by DC motors driven by DC generators. those are, in turn, driven by diesel engines. Which of the following is the reason for using such a configuration instead of AC generator motor sets

the DC configuration provides high torque and good incremental power at low speeds, and performs equally well at high speeds

Which generator has no frequency

to adjust the power of the alternator, adjust the

governor

what kind of load of an alternator has for a negative voltage regulation

capacitive

for two alternators operating in parallel, if the load shared by one of them is to be increased, its field excitation is

to be kept constant but input torque should be increased

what is the formula for the synchronous speed of a motor?

Ns=120f/P

what affects the speed of a rotating field

frequency and number of poles

if the speed of an induction motor increases, what happens to the rotor frequency

decreases

when the frequency of a synchronous motor increases, what happens to its speed

increases

Which of the following is not a reason why single-phase induction motor run

hysteresis

what is the main reason that alternating current replaced DC for general use

AC voltages conveniently transform

Which of the following is not a basic element of transformer

mutual flux

Which of the following transformer has only one winding

auto transformer

what type of transformer bank is used to convert two phase to three phase power

Scott-T

transformers are used to change the value of the following except

power

ideal transformer assumptions do not include

zero reactance of the winding

open circuit test on transformers is conducted to determine

core loss

copper loss of a transformer are determined by means of a/an _____ test

short circuit

to protect the ∆-∆ power transformer against fault, the CT will have

Y-Y connection

an excellent indicator of the condition of the oil in the power transformer is obtained by dividing the IFT (interfacial tension) by the NN (neutralization number). this ratio is known as the ___

Myers index number

the starting/ in rush current of the transformer is generally ____ times of its full load current

also known as Foucault or joule loss, is a phenomenon that occurs when a conductor is exposed to a varying magnetic field, resulting in the generation of circulating currents within the conductor

Eddy current loss

What is the effects on current flow does in reversing the direction of movement of a conductor in the magnetic field of a generator?

It reverses the direction of current flow.

In the transformers,

high tension winding is used near the core

Which of the following motors is generally used in toys ?

shaded pole motor

What device is used to measure the temperature of a motor winding while the motor is in operation?

resistance temperature detector

The electric motor generally used in household food mixer.

universal

21 is the device function number for this relay.

Distance relay

The current flowing in the armature of a dc motor is

A step-down transformer is used to

decrease the voltage

Copper loss of a transformer are determined by means of a/an ____ test.

short circuit

The purpose of providing dummy coils in the generator is

to provide mechanical balance for the rotor

If the per unit impedance is x pu, what is the new per unit impedance when both base power and voltage are doubled

0.5x

Power lost due to alternating magnetization and demagnetization of the core material

hysteresis loss

What is the maximum speed at which a 60 Hz synchronous machine can be operated?

3,600 rpm

Which of the following is NOT a reason why single-phase induction motor run?

hysteresis

which of the following define the meaning of load factor

the ratio of average load to maximum load

which of the following methods of generating electric power from the seawater is more advantageous

tidal power

which of the following cannot have a single unit of 100 MW

diesel power plant

diesel power plant is best suited as

standby

what is the function of the surge tank in the hydro power plant

relieve water hammer pressures in the penstock pipe

which of the following plants will take least time in starting from cold conditions to full load operations

hydroelectric power plant

which power plant requires highest initial cost and minimum cost of fuel transportation

nuclear

Nuclear reactors generally employ

fission

which of the following power plant in a non-renewable energy

nuclear energy

based load plants are designed to supply power at

high capital cost and low operating cost

which of the following is/are the most important factor/s to be considered in the selection of fuel for power plants I. cost of fuel II. Calorific value of fuel

both I and II

the depletion region of a junction diode forms the ____ of the capacitor

dielectric

which of the following define the Fermi energy

the amount of energy which must be given to an electron to move it to conductor band

an ideal full wave rectifier with a non inductive load has zero transformation losses. what is the efficiency

what is the equivalent of the collector terminal of transistor in FET?

grid

in which type of electronic communications does the information travel in two directions

full duplex

a type of electronics communication in which only one party transmits at a time

half duplex

amplitude modulation generated at a very low voltage or power amplifier is ___ modulation.

low level

which of the following is a primary disadvantage of FM over AM

excessive use of spectrum space

which of the following is primary disadvantage of AM over FM

noise susceptibility

the amount of frequency deviation from the carrier center of frequency in an FM transmitter is proportional to the

amplitude

a type of communication that uses light rather than electricity to communicate is called

fiber optic

which of the following principle will the operation of fiber optic cable is based

reflection

which of the following carries the most number of channels

1 fiber optic

what is the optical source for the transmitting end of an optic fiber cable

LED

what is the most commonly used fiber optic cable

multimode step index

what replaces coaxial cable for terrestrial transmission

point to point wireless transmission

what is the common unit of the sound absorption coefficient

sabine

what contains in each cell site of cellular telephone system

repeater

it refers to a device that merely boost a signal and passes it on

repeater

the master control center for a cellular telephone system is the

mobile telephone switching office

what is the maximum output power of a cellular transmitter

3 watts

The power lost is MORE consider in the design of

the transmission line

the voltage regulation is more considered in the design of

the feeder

What is/are the main reason/s for using high voltage in the transmission of power in the grid system? I. to transmit bulk power with minimum line losses II. Increase system reliability

I only

Increasing the voltage of the transmission system to double of 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

An unconventional conductor consists of three strands arranged vertically. Find the GMR in terms of radius r of and individual strand.

1.704r

The value of inductance in three-phase line is ____ times the loop inductance for single-phase line.

1/2

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 inductors are interchanged at regular intervals in the line. This practice is known as I. Transposition II. Interchange

A two terminal pair of network of a transmission line can be represented by

either A or B

The effective resistance of conductor is increased by

both A and B

AC system has the following disadvantages over DC system.

charging current exists

An ACSR conductor having seven steel strands surrounded by 25 aluminum conductor is specified as

25/7

An ACSR conductor has (n-1) layers around its single center strand, the total number of strands will be

3n2 - 3n + 1

What is ACSR conductor stand for?

Aluminum Cable Steel Reinforced

Which of the following is NOT considered in analyzing a short transmission line?

shunt admittance

In a transmission line of negligible resistance, the surge impedance will be

square root of L/C

The hazards exist only during the period of time the _____ is there.

fault

Which of the following type of fault that used only the equivalent positive impedance of the circuit in the short-circuit calculation?

Three-phase fault

Which of the following type of fault used only the equivalent positive and negative sequence impedance of the circuit in the short-circuit calculation?

Line to line

Zero-sequence current will flow in a transmission line when there is

double line to ground fault

What can usually be assumed as the driving or source voltage for fault and voltage calculations in per unit method?

1 p.u.

For a transmission line terminated in its characteristic impedance, which of the following statement is incorrect:

The energy distribution between magnetic and electric field is not equal.

100

Guy wire is used in the construction of distribution lines for what purpose?

supporting the pole

Math

Math

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