For a single phase capacitor start induction motor which of the following is valid ?
To avoid arcing, connect suitable value of in earthing
What is the value of the current I in the circuit shown below ?
In the following type of conductors the corona is minimum in
Consider the following w.r.t. the circuit as shown below
1. VR 100√ 2V=
2. | I |rms = 2A
3. L = 0.25H
Which of the above statements is/are correct?
If the time delay of relay with TMS setting 0.1 is 10 second then what is the time delay whenthe TMS setting is changed to 0.5
The machine used in wind will is
In an RLC series resonant circuit, if the maximum stored energy is increased by 10%and at the same time, the energy dissipated per cycle is reduced by 10%, it will result in whichone of the following ?
Consider the following components Out of these components, which component(s)can be common for primary & back up protection
In a series resonance circuit, at resonance selectivity Q is equal to
Positive sequence terminal voltage is zero in
.Most economical load in the underground cable is
The friction experienced by a body, when in motion, is known as
certain network consist of a large number of ideal linear resistances, one of which is
designated consumed by R is P1 when only the first source is active, and P2 when only the
second source is active, if both source are active simultaneously, then the power consumed by R
is
Consider the following statement about D'Arsonval Movement
1. It is best suited for d.c. current measurement
2. It responds to the average value of current
3. It could be used for power measurements Which of these statements is/are correct
Torque/weight ratio of an instrument indicates
A current transformer has a phase error of +3º. The phase angle between the primary andsecondary current is
The direction of rotation of a d.c. series motorcan be reversed
A three phase transformer having zero sequence impedance of Zo has the zero-sequencenetwork as shown in the figure below. The connection of its windings are
The transformer laminations are insulated from each other by
A coil with certain number of turns has a specified time constant. If the no. of turns isdoubled, its time constant would
The technique of adding a precise amount of time between the trigger point and the beginningof the scope-sweep in a CRO is known as
In a CE (common emitter) transistor, VCC = 12V and the zero signal collector current is 1mA. Determine the operating point when collector load (RC) is 6 KW
A 100 H.P. motor with a synchronous speed of 720 rpm at 50 Hz has 96 stator slots with4 conductors per slot and 120 rotor slots with 2 conductors per slot. If the full load efficiencyis 0.92 and the p.f. is 0.9 lagging, the current per phase when the stator is star connected to3-phase, 500V supply will be
Which of the following application requires high starting torque ?
Which DC motor will be preferred for machine tools ?
The empty space between the plates of a capacitor is filled with liquid of dielectricconstant K the capacitance of capacitor
If current through the operating coil of a moving iron instrument is doubled, the operating forcebecomes
A magnetic needle is kept in a uniform magnetic field. It experiences
Disadvantage of low p.f. is
For improvement of power factor
A 4-pole 500V shunt motor has 720 wave connected conductors on its armature. The fullload armature current is 60A and flux per pole is 0.03 Wb. The armature resistance is 0.2Wand the contact drop per brush is 1V. What is the back emf ?
In an autotransformer of voltage ratio
the fraction of power transferred
inductively is proportional to
Stepped core is used in transformers in order to reduce
A make break switch is provided to disconnect the battery when the meter is not in use is
Which instrument is the cheapest, disregarding the accuracy
In dc machines, the armature reaction mmf is
Inductance affects the flow of direct current at the time of
A centre zero ohmmeter connected in the rotor circuit of 6-pole 50 Hz induction motor makes30 oscillations in one minutes. The rotor speed is
A coil of resistance 20W and inductance 0.8 H is connected to a 200V DC supply. The rate
of change of current at t = 0+ is
What should be the value of resistance R, in the above circuit if it has to absorb the maximum
power from the source
The torque on the rotor of a 3- W motor is more constant than that of a single phase motorbecause
When the secondary coil of a transformer is short circuited, the primary inductance
Q-factor of a parallel tuned circuit can be increased by
Air blast circuit breakers for 400 KV power system are designed to operate in
An overhead line conductor has an inductance per unit length of L Henry. If the entire medium
around the conductor is filled with a dielectric material of permittivity (E), then the inductance
will be
In two-wattmeter method of power measurement one of the wattmeter will shownegative reading when the load pf angle is strictly
A reactance relay is
To limit current chopping in vacuum circuit breakers, the contact
The main difference between speed-time curves of mainline service as compared to suburbanservices in
Which of the following relay has directional feature
Carbon brushes are preferable to copper brushes because
A power plant has a maximum demand of 15 MW. The load factor is 50% and the plantfactor is 40%. The operating reserve is
The starting torque of a servomotor under unbalanced operation is proportional to
Quadrilateral speed-time curve is the closer approximation for
Travelling crane is used for lifting and moving heavy loads. It uses
For Domestic wiring method commonly used is
The time taken for a surge to travel a 600 km long overhead transmission link is
Ripple factor of half wave rectifier is
Which one is unipolar transistor
A polarized electrolytic capacitor can be used
A moving coil instrument gives full scale deflection with a current of 100 mA when thepotential difference across its terminals is 50 mV. Calculate the shunt resistance to enablethe instrument to read upto 100 A
Which of the following motors are used in tape recorders
Which motor would you select for vacuum cleaner
A tank circuit consist of
The commulator in a dc machine acts as
Ferranti effect on transmission line is a phenomenon which represents
EHV cables are filled with thin oil under pressure
Arcing on transmission lines is prevented by connecting a suitable
In half wave rectifier, if an a.c. supply is 60 Hz, then what is the a.c. ripple at output ?
A power supply has full load voltage of 24V. What is the no load voltage for 5% regulation?
For an existing ac transmission line, the string efficiency is 80%. If dc voltage is supplied forthe same set up, the string efficiency will be
When excitation is altered in an alternator connected to an infinite line, it provides acorresponding change in
Lightening surges are arrested by
The rms value of a half wave rectified currentis 10A. Its value for full wave rectification would be
176. For the wave given below, the rms value will be
177.The equation for 25 cycles current sine wave having rms value of 30 amperes will be
A 220 V series motor takes a current 35 amp and runs at 500 rpm. Armature resistance =0.25W and series field resistance = 0.3W. If iron and friction losses amount to 600W. Whatis the armature torque
Illumination level required for precision work is around
Lumen/watt is the unit of
A DC generator used for ac welding should have
The load taken by welding transformer is
In rectifier circuit shown above, what should be minimum peak-inverse voltage (PIV) ratingof the diode
In an open circuited p-n junction diode space charge density at the junction is
In an HVDC system
In order to have lower cost of power generation
Mho relay is usually employed for the protection of
The making and breaking currents of 3- f ac circuit breakers in power system arerespectively in what form
For a fault in power system, the term critical clearing time is related to
A cable has inductance of 0.22 mH per km and capacitance of 0.22 mF per km. The surgei mpedance of the cable is
The shunt winding of a motor has a resistance of 85W at 22ºC. When the motor runs at fullload, its resistance increases to 100 ohms. The resistance temperature coefficient of winding perOºC is 0.004. The rise in temperature of the winding will be nearly
Temperature coefficient of resistance is expressed in terms of
For the same peak value of voltage which wave will have the highest rms value ?
A wire 2.5m long is bent into a square. A current of 100 A flowing through the wire will produce
a magnetising force at the centre of the square, equal to
Common base configuration is little used because
The decrease in terminal voltage of a shunt generator is due to
The armature voltage control is considered as suitable, in case the dc machine is driven at
Interpoles are usually wound with
If the flux of dc motor approaches zero
Which of the following is not a routine test on transformers
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