WorksheetsEIE Quiz 1
Total questions: 25
Worksheet time: 19mins
Which of the following rule is used to determine the direction of rotation of D.C motor?
Coloumb’s Law
Lenz’s Law
Fleming’s Right-hand Rule
Fleming’s Left-hand Rule
Which DC motor is preferred for constant speed?
Series motor
Compound motor
Shunt motor
Differential motor
The torque developed by a d.c motor is directly proportional to
Flux per pole x Armature current
Armature resistance x Applied voltage
Armature Resistance x Armature current
Square of armature resistance
EMF equation for DC generator is -------------
Eg = PΦNZ / 120A
Eg = PΦNZ / 60A
Eg = PΦNA / 60Z
Eg = PΦNZ / 160A
Rotor of PMBLDC motor is
Permanent magnet
Electro magnet
Armature winding
Field winding
As the speed of an alternator increases, the frequency
Increases
Decreases
Remains constant
May increase or decrease depending on the power factor
A machine without commutator, providing an ac emf to the external circuit is called as
D.C. generator
Alternator
Transformer
Synchronous motor
Slip is defined as
the difference between synchronous speed and rotor speed
the difference between rotor speed and synchronous speed
synchronous speed - rotor speed / rotor speed
(rotor speed - synchronous speed ) / synchronous speed
3-phase induction motor is a self-starting machine
True
False
The principle of operation of three phase induction motor is similar to........
Synchronous motor
Repulsion start induction motor
transformer with a shorted secondary
capacitor start induction run motor.
The torque developed by a single-phase motor at starting is
less than the rated torque
More than the rated torque
zero
None of the above
Which of the following the magnetic field current is supplied by a separate DC power source,
Induction machines
synchronous machines
Transformers
AC genrators
Which answer is correct to explain about operation of Synchronous Generator
The rotating magnetic field & the rotor rotate at the same speed
The rotating magnetic field speed is faster than rotation of rotor
The rotating of rotor is faster than magnetic field speed
The rotor rotate when current induced at rotor.
In a transformer, Copper losses are also known as
variable loss
iron loss
eddy current loss
losses in shunt parameter
Which one is not correct for auto transformer
It has better voltage regulation in resistance and reactance of the single winding is less
It has lower efficiency than two winding transformer.
Used only for slight variation of the output voltage from input voltage
It is also used as a voltage regulator
The sum of Hysteresis and Eddy current losses are also called
Ohmic loss
Heat loss
Copper loss
Constant loss
The main advantage of auto transformer over a two winding transformer is
Hysteresis losses are reduced
Saving in winding material
Copper losses are negligible
Eddy losses are totally eliminated
The efficiency of a transformer is maximum when
It runs at half full load
it runs at full load
its Cu loss equal iron loss
it runs over load
Ideal Transformers will have_________ efficiency
2%
5%
98%
100%
How will you reduce core loss in the transformer?
By using silicon steel
By reducing the size of winding
By increasing the size of the winding
The rating of transformer may be expressed in ____________.
kW
KVA
KVAR
HORSE POWER
What will happen if the primary of a transformer is connected to D.C supply?
Transformer will operate with low efficiency
Transformer will operate with high efficiency
No effect
Transformer may start to smoke and burn
In BLDC motor, Electronic commutation based on __________
Hall position sensors
Temperature sensors
ecoders
A brushless motor is more efficient than a brushed motor because...
There is less energy lost inside the motor due to friction and heat.
There is less power used to spin the motor.
There is less noise created in spinning the motor.
This is an incorrect statement. Brushed motors are more efficient.
The starting torque of a squirrel-cage induction motor is
Full-load torque
Slightly more than full-load torque
Low
Negligible
