WorksheetsEIE Quiz 1 (Activity 2)
Total questions: 40
Worksheet time: 30mins
For a transformer copper losses are also known as
variable loss
iron loss
eddy current loss
losses in shunt parameter
The magnetic material for the core needs to be made of soft iron where its permeability is high
to reduce eddy current loss
to reduce hysteresis loss
to avoid fringing in the core
to reduce copper loss in the winding
Why transformers work with A.C. current but not D.C.
A.C current produces changing magnetic field.
D.C current produces changing magnetic field.
D.C current is weak
A.C current is powerful
Transformer is a device which transforms A.C electric power of one circuit to another , keeping the _______ same.
Voltage
Current
Frequency
Laminated insulation are normally used in the transformer:
To reduce the hysteresis effect
To increase the hysteresis effect
To reduce the effect of eddy current
To increase the effect of eddy current
If dc voltage is applied to the primary of a transformer it may:
Work
Burn the winding
Give lower voltage on the secondary side
Give higher voltage on the secondary side
Transformer ratings are usually expressed in terms of :
Voltage
KVA
kWh
KW
In _________ Transformer Losses are Zero.
Practical
Ideal
Isolation
Auto
What is the material used for construction of transformer core?
Aluminium
Copper
Iron
Wood
Efficiency of a transformer is
(output current)/(input current) x100%
(output voltage)/(input voltage) x100%
(output loss)/(input loss) x100%
(output power)/(input power) x100%
What is the purpose of voltage regulation in an autotransformer?
To decrease the output voltage
To maintain a constant output voltage despite variations in input voltage.
To increase the input voltage
To convert AC to DC
What are the advantages of using an autotransformer?
More prone to breakdowns, less durable, and difficult to maintain
No difference in efficiency, cost, or size
Less efficient, expensive, and larger in size
More efficient, cost-effective, and smaller in size
Current transformers are __________________
parallel connected type of instrument transformers
series connected type of instrument transformers
parallel connected normal transformers
series-parallel connected type of instrument transformers
The purpose of the transformer core is to provide
Low reluctance path
High inductive path
High capacitive path
High reluctance path
Which of the following transformer, Buchholz’s relay can be fixed on?
Welding transformers
Oil cooled transformers
Auto-transformers
Air-cooled transformers
An ideal transformer will have maximum efficiency at a load such that
copper loss > iron loss
cannot be determined
copper loss = iron loss
copper loss < iron loss
Which of the following is the main advantage of an auto-transformer over a two-winding transformer?
Eddy losses are totally eliminated
Copper losses are negligible
Hysteresis losses are reduced
Saving in winding material
Total windings present in an autotransformer are
1
2
3
4
Two-winding transformer of a given VA rating if connected as an autotransformer can handle
Higher VA
Lower VA
Same VA
Cannot be found
Ratio of winding material needed for autotransformer to thr two winding transformer is
1- V2/V1
1- N2/N1
1- V2/V1 and 1- N2/N1
1- V1/V2
Which of the following quantities cannot be measured using Multi-Meter:
Resistance
Voltage
Current
Power Factor
In a Circuit, Ammeter should be always connected in ____ arrangement
Series
Parallel
Either in Series or in Parallel
Can be connected in both
Instrument used to measure D.C alone
MI
PMMC
Induction type
Dynamometer type
Principle: Two iron pieces are kept with close proximity in a magnetic field get magnetized with the same polarity. Whose principle is this?
PMMC
PMMI
PMMI- Attraction Type
PMMI- Repulsion Type
A dynamometer type wattmeter consists of ________
only potential coil
potential and current coils
only current coil
no coils
A pointer of an instrument once deflected returns to zero position, when the current is removed due to
Action of gravity
Mass of the pointer
Controlling Torque
Damping Torques
Define Measurement
Measurement is the process by which one can convert physical parameters to meaningful numbers.
Measurement is the process by which one can convert electrical signals to physical parameters.
Measurement is the process by which one can convert physical parameters to electrical signals.
Measurement is the process by which one can convert physical parameters to other physical parameters.
A measuring system consists of
Sensors
Variable conversion elements
Signal processing elements
All of these
An instrument in which the value of ethnical quantity to be measured can be determined from the deflection of the instrument when it has been precalibrated by comparison with an absolute instrument
Absolute instrument
Secondary instrument
Recording instrument
Integrating instrument
The advantages of moving coil permanent magnet type instrument are
Low power consumption
No hysteresis loss
Efficient eddy current damping
All of the above
What is the function of the deflecting system in the principle operation of a PMMC instrument?
It provides the controlling force to move the pointer.
It provides the damping torque for steady-state positioning.
It generates the deflecting torque proportional to the measured quantity.
It brings the pointer back to the zero position.
Supply voltage in an energy meter is
constant always
can fluctuate
zero always
depends on the load
Instrument transformers provide _
electrical isolation from low rated winding
electrical isolation from high rated winding
electrical isolation from medium rated winding
no electrical isolation at all
Potential transformers are used to measure
high voltages
low voltages
high currents
low currents
Energymeter is a / an
Indicating instrument
Integrating instrument
Recording instrument
Measuring instrument
The S.I. unit of power is
Henry
Coulomb
Watt
Watt-hour
Why we need to choose the right instrument for the right application of measurement?
To get less cost and time when doing measurement
To obtain the best measurement
To ensure less error on the measurement
To guarantee the safety of measurement
Torque means........
twisting or turning force about an axis
electromagnetic force
external force to move
internal force to move
