71. P= QHg is the water power equation. Head 'H' is measured in meter, 'g' gravity constant is measured in meter per second square, then the measuring unit of 'Q' flow rate of water is ?
the measuring unit of 'Q' flow rate of water is Cubic metre per second.
72. Z1 and Z2 are connected in series to form a load. A wattmeter's current coil is connected in series with the load, whereas its pressure coil is connected across Z2. The wattmeter reads ?
The wattmeter reads power consumed by Z2 because in load Z2 both current from C.C. and voltage from P.C. are present while in Z1 only current. Thus wattmeter read only Load of Z2
73. Three lamps are connected in series across a 120 V supply and take a current of 1.5A. If the resistance of two of the lamps is 30 Ω, what is the resistance of the third lamp ?
Three lamps are connected in series across a 120 V supply and take a current of 1.5A.
So Tatal resistance of circuit =120/1.5 = 80 Ω
2 lamp resistance = 2x30 = 60 Ω
the resistance of the third lamp = 80-60 = 20 Ω
.
74. In the circuit shown, the pressure coils of two wattmeters are connected to ?
75. The skin effect does not depends upon ?
Skin effect does not depends upon Operating voltage
Frequency – Skin effect increases with the increase in frequency. Diameter – It increases with the increase in diameter of the conductor. The shape of the conductor – Skin effect is more in the solid conductor and less in the stranded conductor because the surface area of the solid conductor is more.
Skin effect is directly proportional to diameter of conductor.
It is proportional to frequency of supply.
skin effect increases with the increase in frequency.
It Depends on the shape of the conductor.
76. Identify the important feature of a DC series motor ?
DC series motors, field winding is connected in series with the armature, i.e. Ia = If. Therefore, before magnetic saturation of the field, flux ɸ is directly proportional to Ia. Hence, before magnetic saturation Ta α Ia2.
In DC series motors, (prior to magnetic saturation) torque increases as the square of armature current, these motors are used where high starting torque is required.
77. The trade name of Nickel-Copper alloy, that is used as a heating element is ?
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. Its main feature is the low thermal variation of its resistivity, which is constant over a wide range of temperatures.
Surface resistivity: 0.49 μΩ·m
Cupronickel Cupronickel or copper-nickel (CuNi) is an alloy of copper that contains nickel and strengthening elements, such as iron and manganese.
Kanthal is the trademark for a family of iron-chromium-aluminium (FeCrAl) alloys used in a wide range of resistance and high-temperature applications. Kanthal FeCrAl alloys consist of mainly iron, chromium (20–30%) and aluminium (4–7.5 %).
78. 'H=__is the expression for magnetic field due to an infinite linear current carrying conductor ?
79. Which of the following lamps has shortest/less life span is working hours ?
Incandescent bulbs generally have the shortest lifespans. The average incandescent bulb light span is approximately 750 -2,000 hours..
80. In the speed-time curve of a train, speed in __ and time in ___ are plotted ?
In the speed-time curve of a train, speed in km/s and time in sec are plotted.
1 2 3 4 5 6 7 8 9 10
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