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WorksheetsELECTRICAL ENGINEERS PRE-BOARD EXAMINATION AUGUST 2013
Total questions: 22
Worksheet time: 11mins
To reverse the direction of rotation of a three-phase induction motor, it is necessary to
Interchange all the three line connections
Reverse the polarity of the rotor circuit
Increase the resistance of the rotor circuit
Interchange any two of the three line connections
Transformers are rated in
KW
KV
KWHR
KVA
In a series RL circuit, the inductor current _________ the resistor current.
Lags
leads
is equal to
is negative of
The power factor of incandescent bulb is
0.8 lagging
0.8 leading
unity
zero
The law that induces emf and current always opposes the cause producing them was discovered by
Lenz
Maxwell
Faraday
Ohm
Temperature coefficient of a conductor is defined as the
increase in resistance per ohm per degree centigrade
increase in resistance per degree centigrade
increase in resistance per degree absolute
decrease in resistance per ohm per degree centigrade
Open conductors run individually as service drops shall be _______.
I. insulted II. bare III. covered
I only
II only
III only
either I or II
The power factor of an alternator is determined by its
speed
load
excitation
prime mover
The speed of a synchronous motor
reduces as load increases
increases as load increases
adjusts itself to new equilibrium speed whenever load changes
always remains constant
The efficiency of thermal power plant is approximately
10%
30%
60%
80%
One advantage of distributing the winding in alternator is to
Reduce harmonies
improves voltage wave from
reduce the amount of cooper
decreases the value of the voltage
Impurities in an electrolyte can cause an internal short circuit condition called
depolarization
electrolysis
local action
polarization
The turn-on voltage of a Ge junction diode is ______volt
0.7
0.3
1
0.1
A mode of communications in which either party can hear while taking, thus allowing one party to instantly interrupt the other at any time, is called
Half simplex
Full simplex
Full duplex
Half duplex
A device that repeatedly reverse the polarity of a magnetic field in order to keep a dc motor rotating is known as
a solenoid
a commutator
an armature coil
a field coil
is the device function number assigned by ANSI to this relay;
lock out relay
undervoltage relay
directional relay
differential relay
Wind mils in addition to proper gearing is the best driver for
dc generator
synchronous generators
inductance generators
rotary rectifiers
Bundled conductors in EHZ transmission lines results to
reduce capacitance
increase inductance
increase capacitance
increase resistance
The surge impedance of an underground cable is around
50
25
400
100
A contact device installed at the outlet for the connection of a single attachment plug.
pendant
switch
receptacle
plug
When carrier wave is modulated at 100%, its power is increased by ____ percent.
100
150
50
0
Differential relays are installed to protect the equipment against.
reverse current
internal faults
overcurrent
no voltage
