A current density of _________ is used for large power transformers with forced circulation of oil or with water cooling coils
1.5 to 2.5 A/mm²
3.5 to 4.5 A/mm²
4.0 to 5.0 A/mm²
5.4 to 6.2 A/mm²
Q.2.
In a Weston frequency meter, the magnetic axes of the two fixed coils are
parallel
perpendicular
Q.3.
Which of the following methods is used for air cooling of turbo-alternators ?
One sided axial ventilation
Two sided axial ventilation
Multiple inlet system
All of the above
Q.4.
A Weston synchronoscope is a
moving coil instrument
moving iron instrument
dynamometer instrument
none of the above
Q.5.
To measure a resistance with the help of a potentiometer it is
necessary to standardise the potentiometer
not necessary to standardise the potentiometer
necessary to use a volt ratio box in conjunction with the potentiometer
none of the above
Q.6.
Wattmeter cannot be designed on the principle of
electrostatic instrument
thermocouple instrument
moving iron instrument
electrodynamic instrument
Q.7.
In a 3-phase power measurement by two wattmeter method the reading of one of the wattmeter was zero. The power factor of the load must be
unity
0.5
0.3
zero
Q.8.
If the current in a capacitor leads the voltage by 80°, the loss angle of the capacitor is
10°
80°
120°
170°
Q.9.
In a dynamometer 3-phase power factor meter, the planes of the two moving coils are at
0°
60°
90°
120°
Q.10.
In Weston synchronoscope the moving coil is connected across
bus-bars
incoming alternator
fixed coils
any of the above
Q.11.
Which of the following instruments indicate the instantaneous value of the electrical quantity being measured at the time at which it is being measured ?
Absolute instruments
Indicating instruments
Recording instruments
Integrating instruments
Q.12.
A phase shifting transformer is used in conjunction with
potentiometer
Drysdale potentiometer
co-ordinate potentiometer
Crompton potentiometer
Q.13.
An instrument transformer is used to extend the range of
induction instrument
electrostatic instrument
moving coil instrument
any of the above
Q.14.
According to Lenz law write the formula for finding emf induced in the coil?
B=ϕ÷AB=\phi\div AB=ϕ÷A
E=−dϕdtE=-\frac{\text{d}\phi}{\text{dt}}E=−dtdϕ
H=MMFLH=\frac{MMF}{L}H=LMMF
MMM=NIMMM=NIMMM=NI
Q.15.
How will you find the magnetic field strength?
B=ϕ÷AB=\phi\div AB=ϕ÷A
E=dϕdtE=\frac{\text{d}\phi}{\text{dt}}E=dtdϕ
H=MMFLH=\frac{MMF}{L}H=LMMF
MMM=NIMMM=NIMMM=NI
Q.16.
How will you find the magnetic flux density?
B=ϕ÷AB=\phi\div AB=ϕ÷A
E=dϕdtE=\frac{\text{d}\phi}{\text{dt}}E=dtdϕ
H=MMFLH=\frac{MMF}{L}H=LMMF
MMM=NIMMM=NIMMM=NI
Q.17.
Write the formula for finding mmf?
B=ϕ÷AB=\phi\div AB=ϕ÷A
E=dϕdtE=\frac{\text{d}\phi}{\text{dt}}E=dtdϕ
H=MMFLH=\frac{MMF}{L}H=LMMF
mmf=NImmf=NImmf=NI
Q.18.
Write the formula for finding emf induced in the coil?
B=ϕ÷AB=\phi\div AB=ϕ÷A
E=dϕdtE=\frac{\text{d}\phi}{\text{dt}}E=dtdϕ
H=MMFLH=\frac{MMF}{L}H=LMMF
MMM=NIMMM=NIMMM=NI
Q.19.
What is the relationship between the VA rating of a transformer and the internal percentage impedance Z?
VA ∝1/ Z
VA ∝Z
VA ∝2Z
VA ∝ Z/2
Q.20.
How can the direction of a capacitor start single phase motor be reversed?
Reverse the connection to the capacitor
Reverse the connection to the start winding
Reverse the polarity of the supply
Reverse the connection of the start and run windings
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