ELECTRICAL 6

Gaviola Jayson, Alab · 100問 · 2年前

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a substance that contains atoms with several bonds of electrons but with only one valence electron is

conductor

when a conductor is stationary and the magnetic field is moving or changing the emf induced is called______ induced emf

statically

a coulomb

is an extremely large number of charge carriers

fault level means

fault mva

which plant can never have 100% load factor

peak

the unit of elastance is

daraf

all magnetic fields origantes from

moving electric charge

an ion

can have either positive or negative charge

an induction motor is analogous

two winding transformer with short circuit secondary

the dc armature winding in which the coil sides are placed a pole pitch apart is called ____ winding

full-pitch

sensitivity of a voltmeter is expressed as

ohms/volt

when the excitation of an unloaded salient pole synchronous motor suddenly gets disconnected then

the motor stops

the ratio of lumens reaching the workplane divided by the total lumens generated by the light is

coefficients of utilization

there is no zero sequence component of the fault current for ___ fault

line to line

the capacitor in a series rc circuit at steady state is

open circuit

during load shedding

some loads are switched off

which of the following is not the method of arc dispersion

use of rectifier

which of the following is not the method of arc dispersion

use of rectifiers

an external resistance is add in series with the field of a decision motor and the motor runs the effect of resistance is

to increase the speed of the motor

on tripling the number of turns of a coil the inductance

9 times as large

what is the relative permitivity of vacuum

unity

lap winding is best suited for ___voltage _____current dc motors

low high

the minimum armature current of a synchronous motor corresponds to operation at

unity power factor

which waveform will have the minimum rms value if they have the same value of voltage

triangular wave

which of the following is an active element of a circuit

ideal current source

barrier potential of silicon diode is

0.7v

in electroplating the positive electrode is called the

anode

if the input of the prime mover of an alternator is kept constant but excited citation is increased then

kva will be lagging

the armature current drawn by any dc motor is proportional to

torque required

the current flowing in the armature conductors of a dc motor is

the synchroscope is an instrument used to indicate the

phase relationship between two voltages

what is the maximum allowable voltage drop for feeder

what is the maximum allowable voltage drop for lighting circuit

the ampere are capacity of battery depends on

the area of the plates

a material best suited for manufacturing of fuse wire is

silver

the current flowing in L and C at parallel resonance are

equal

In a series RLC circuit the impedance at resonance is

minimum

the current in RLC series circuit at resonance is

maximum

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

gas turbine

which of the following relay is used in transformers

buchholz relay

the heat required to raise 1 gram of water at 1 c

calorie

heating value of coal largely depends on

ash content

the open circuit condition of thevenin theorem all sources of emf in network are replaced by

their internal impedance

a direct lighting fixture directs atleast

90% of light downward

one decibel represents a power ratio of

1:26:1

semiconductors like silicon and germanium are

tetravalent

in parallel rc circuit as the value of frequency increases the powerfactor

decreases

this device is used to reflect back surges into the line

choke coil

what is the device function number of overvoltage relay

the load of a certain transformer is reduced to 50% the copper loss would become

0.25 times

shunt generators are used where the main requirement is constant

voltage over a narrow load range

transmission voltage level of 1000 kv is categorized as

ultra-high voltage

the efficiency of thermal power plant is approximately

30%

when the relative permeability of a material is slightly less than one it is called ______material

diamagnetic

the rms value of sinusoidal ac current is equal to it's value at an anghle of

one of the advantages of distributing the winding in an alternator is to

improve voltage waveform

a circuit breaker will normally operate

whenever fault in the line occurs

two wattmeters can be used to measure 3 phase power for a

balanced and unbalanced load

what is the nature of the current flowing in the armature of dc machine

alternating current

a magnetic field exist around

moving charges

inductance affects the direct current flow at the time of

turning on and off

In a radio a gang condenser is type of

air capacitor

a material commonly used for shielding or screening magnetism is

soft iron

one advantage of secondary cell is that it

can be recharged

what type of core is used for high frequency transformer

air core

In television system channels 2-13 are classified as

VHF

The basic function of circuit breaker is to

extinguish the arc

Air used in air blast circuit breaker

must be free from moisture

What is the counterpart of magnetic flux in an electric circuit

Current

In a parallel circuit the potential difference across resistance

is always constant

What is the maximum distance between two receptacles in a single family dwelling unit

1.8 m

The RMS value of sinusoidal wave is equal to ___ of maximum value

0.707

In two wattmeter method the readings of the wattmeters will be identical when

power factor is unity

In two wattmeter method, the readings of the wattmeter will be identical when

power factor is unity

what is the maximum distance between two receptacles in a single family dwelling unit

1.8m

What is the minimum clearance between two receptacles fixture and the nearest point of a storage space of a closet

150 mm

What is the derating factor in each of 7-9 conductors in a raceway

70%

What is the maximum number of conductors in a raceway that does not need to be derated

34.5kV to 69kV is classified as

high voltage

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

decreases

one advantage of distributing the winding in an alternator is to

improve voltage waveform

if the voltage is doubled the ampacity of a conductor

remains the same

the purpose of a grid system is to

interconnect the power stations

as the load is increased the speed of a dc shunt motor will

reduce slightly

if the field of a synchronous motor is under-excited the power factor will be

lagging

In dc machines lap winding is used for

low voltage high current

wye-wye power transformers are protected by current transformers having___connection

delta-delta

which of the following equipment is not part of megger

a coil of high inductance

for an unbalanced load which connection is suitable

4 wire wye connection

the meter movement in an illumination meter directly measures

current

an electrical insulator can be made a conductor

by ionizing it

to reverse the direction of rotation of a three-phase induction motor, it is necessary to

interchange any two of the three line connection

transformers are rated in

KVA

In a series RL circuit the inductor current____ the resistor current

is equal to

the power factor of incandestent bulb is

unity

the law that induces emf and current always opposes the cause producing them was discovered by

lenz

open conductors run individually as service drops shall be

insulated and covered

Temperature coefficient of a conductor is defined as the

increase in resistance per ohm per degree centigrade

the power factor of an alternator is determined by its

load

100

the speed of a synchronous motor

always remains constant

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