61. 'Creeping' is a term related to .... instruments ?
Creeping in Induction type energy meter is the phenomenon in which the aluminium disc rotates continuously when only the voltage is supplied to the pressure coil, and no current flows through the current coil.
In other words, the creeping is the kind of error in which the energy meter consumes a very small amount of energy even when no load is attached to the meter.
62. ...works on the principle of dynamically induced EMF ?
All the generators work on the principle of dynamically induced emf.
... Whenever a conductor cuts magnetic flux, dynamically induced emf is produced in it according to Faraday's laws of Electromagnetic Induction.
This emf causes a current to flow if the conductor circuit is closed.
63. Which of the following heating element has lowest operating temperature ?
#-Graphite has a melting point similar to that of diamond of around 3600°C, at which point it sublimes rather than melting.
#-Kanthal is a ferritic iron-chromium-aluminium alloy (FeCrAl alloy) for use at temperatures up to 1400°C the melting point of Kanthal is 1,500 °C
#-Constantan or Eureka is a Cupronic alloy usually consisting of few metals and chemicals melted togather at a very high temperature and pressure to form alloy.
the melting point of Eureka is 1300 °C.
Constantan is a proprietary name for a copper–nickel alloy also known as Eureka, Advance and Ferry.
It usually consists of 55% copper and 45% nickel.
#-A common nichrome alloy is 80% nickel and 20% chromium, by mass, but there are many other combinations of metals for various applications. Nichrome is consistently silvery-grey in colour, is corrosion-resistant, and has a high melting point of about 1,400 °C (2,550 °F).
Hence Eureka has the least range of temperature.
64. Two coils are said to be `magnetically isolated', provided the coefficient of coupling K ?
The fraction of magnetic flux produced by the current in one coil that links with the other coil is called the coefficient of coupling between the two coils. It is denoted by (k). ... when k=0, the flux produced by one coil, does not link at all with the other coil and thus the coils are said to be magnetically isolated.
65. If the connected light load in a house is 3000W and power sub-circuit load 6000W, then what is the number of sub-circuits required ?
Indian Electricity Rules specify that the maximum load on a light/fan sub-circuit should not exceed 800 watts and the number of points should be limited to 10.
Hence for light load number of sub-circuit = 3000/800 = 3.75 = 4
Indian Electricity Rules specify that the maximum load on a power sub-circuit should not exceed 3000 watts and the number of outlets should be limited to two.
For the power sub-circuit load number of sub-circuit = 6000/3000 = 2
Total subcircuit = 4 + 2 = 6
66. The input for a condenser in a steam power plant comes from a/an ?
A surface condenser is a commonly used term for a water-cooled shell and tube heat exchanger installed to condense exhaust steam from a steam turbine in thermal power stations
67. type of single phase induction motor operates at better power factor at full load ?
The power factor of induction motors varies with load, typically from around 0.8 or 0.90 at full load to as low as about 0.20 at no-load, due to stator and rotor leakage and magnetizing reactances.
Power factor can be improved by connecting capacitors either on an individual motor basis or, by preference, on a common
The capacitor-start capacitor-run motor actually operates on the principle of a ... Since the capacitor remains connected in the circuit at all times, the motor power factor is close to unity.
68. If a zero-centred voltmeter has a scale from - 5V to 5V, then the span of it is ?
Voltage Scale Span of instrument = Vmax − Vmin
Given
Vmax = 5 V
Vmin = −5V
Span = 5 −(−5) = 10 V
69. The scheduled speed of a train is ?
Schedule Speed:
The ratio of distance covered between two stops and total time of run including time of stop is known as schedule speed.
From above it is obvious that the schedule speed is always smaller than the average speed.
Average speed = (Distance between stops)/(Actual time of run)
Schedule speed = (Distance between stops) /(Actual time of run + Stop time)
70. For a three phase induction motor slip at No Load slip ÷ at Full Load ?
The difference between synchronous speed & rotor speed is called as slip speed.
And if this slip speed is measured w.r.t synchronous speed, then it is called as slip (s).
Therefore, slip=s=(Ns-N)/Ns
N = Ns(1 − s)
At start, the motor is at rest and hence its speed N is zero.
s = 1 or 100% ( start)
While s = 0 gives us N = Ns. which is not possible for an induction motor
Practically motor operates in the slip range of 0.01 to 0.05 i.e. 1 % to 5 %. The slip corresponding to the full load speed of the motor is called full load slip.
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