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The charge on an electron is known to be 1.6 × 10–19 coulomb. In a circuit the current flowingis 1A. How many electrons will be flowing through the circuit in a second ?
Pyrometer is used for measurement of
The voltage and current waveforms for an elements are shown in the figures
The circuit element and its value are
A magnetic ring has a mean circumference of 20 cm and a cross section of 20 cm2 and has 800 numbers of turns of wire. When the exciting current is 5A, the flux is 2 mWb. The relative permeability of iron is nearly
Random error is
A semiconductor device made out of a material having very high temperature coefficient of resistance is
One single-phase energy meter operating on 230 V and 5A for 5 hours makes 1940 revolution. Meter constant is 400 rev/kWh. The power factor of the load is
In a junction transistor, the collector cut-off current 'ICBO' reduces considerably by doping the
In a D.C. generator all of the following could be the effects of iron losses except
The losses occurring in a D.C. generator are given below which loss is likely to have highest proportion at rated load of the generator
In a D.C. generator the critical resistance can be increased by
A series resonant circuit has an inductive reactance of 1000W, a capacitive reactance of 1000W and a resistance of 0.1W. If resonant frequency is 10 MHz, then the bandwidth of the circuit will be
Consider the network given below
The time constant of the circuit is
Two bulbs marked 200 watt, 250 volts and 100 watt -250 volts are joined in series to 250 volts supply. Power consumed in circuits is
Three equal resistors connected in series across a source of emf together dissipate 10 watts of power. What would be the power dissipated in the same resistors when they are connected in parallel across the same source of emf ?
In a transmission system, the weight of copper used is proportional to
If the frequency of a transmission system is changed from 50 Hz to 100 Hz, the string efficiency will
A piece of silver wire has a resistance of 1W. A manganin wire has specific resistance 30 times that of silver. The resistance of a manganin wire of one fourth length and one third diameter will be
Wattless current is possible, only in
If the stator voltage and frequency of an induction motor are reduced proportionately,its
The efficiency and p.f. of SCIM increases in proportion to its
Which of the following lamp gives nearly monochromatic light ?
A auto transformer used with sodium vapour lamp should have
For supply on 25 kV, 50 Hz single phase, suitable motor for electric traction is
The welding transformer used in resistance welding will
The power factor of the load using welding transformer is usually
Pump, blowers and fans are usually called for
In lap windings, the equalizer rings are used to save
A transformer is considered to have a network of series capacitance due to
Stator voltage control for speed control of induction motors is suitable for
The equivalent inductance for the following inductive circuit is
A particular current is made up of two components a 10A dc and a sinusoidal current of peak value of 14.14A. The average value of resultant current is
The unit of a thermal resistance of a semiconductor device is
Assertion (A) : FETs are more suitable at the input stages of millivoltmeter and CROs than
Reason (R) : A FET has lower output impedance than a BJT
With 100% inductive shunt compensation, the voltage profile is flat for
Three phase transformers which cannot be connected in parallel are
In case of a 3-phase short circuit in a system, the power fed into the system is
The most economical limit of power factor correcting is governed by
As per I.E. rules the insulation resistance between conductor and earth should not be less than
As per IE rules, insulation Resistance between earth and conductor should not exceed the 1/5000 time of the current flowing through the conductor.
That is to be measured by the ‘Megger’ instrument.
As per IE rules, 1956 insulation Resistance between earth and conductor should in range of mega Ohms.
IMPORTANT TO REMEMBER:-
One Mega ohm Rule for IR Value for Equipment
Based upon equipment rating:
< 1K V = 1 MΩ minimum
>1KV = 1 MΩ /1KV
Therefore, based on this analogy for Medium and High voltages there is need for Insulation –
Value of insulation Resistance between earth and conductor should not be less than 100 M ohm.
Excess carriers are generated in a sample of N-type semiconductor by shining light at one end. The current flow in the sample will be made up of
The effective resistance between the terminals A and B in the circuit shown in the figure is
In the circuit of figure below, the voltage V(t) is
A dc shunt generator builds up to a voltage of 220 V at no load while running at its rated speed. If the speed of the generator is raised by 25% keeping the circuit conditions unaltered,then the voltage to which the machine would build up will
In normal dc machines operating at full load conditions the most powerful electromagnet is
If the secondary winding of the ideal transformer shown in the circuit of figure has 40 turns, the number of turns in the primary winding for maximum power transfer to the 2 resistor will be
In the circuit shown in the figure, if the ammeter indicates 1A and the voltmeter having an internal resistance of 1KW indicated 100V, then the value of R would be
Thermal runaway is not possible in FET because as the temperature of FET increases
Which of the following statement is correct ?
In an actual transformer the iron loss remains practically constant from no load to full load because
A 2 pole generator with wave wound armature has 51 slots each having 24 conductors. The flux per pole is 0.01 Wb. The speed at which the generator should be run to induce the voltage of 220 should be
For parallel operation, the generators normally preferred are
Which winding on dc generators is preferred for generating large currents ?
The advantage of high voltage transmission is are
The function of steel wire in a ACSR conductor is
The flicker effect of fluorescent lamp is more pronounced at
The level of illumination on a surface least depends on
In resistance welding, aluminium as compared to steel, requires
Pole changing method of speed control is used in
The resistance of series RLC circuit is doubled and inductance is halved, then BW becomes
The input impedance of CRO is nearly
Manometer is used for measurement of
Centrifugal pumps are usually driven by
A 10 mF capacitor was tested by a multimeter using resistance measuring range. If the multimeter reads zero, it can be concluded that
Which of the following induction motors will have the least shaft diameter ?
A 20 kW, 4 pole, 400 V, 60 Hz, 3 phase, 1728 rpm induction motor is connected to 400V, 50 Hz supply, the motor will
In a circuit breaker the active recovery voltage depends upon
Which of the following technique/method is used for the measurement of ac high frequency voltages ?
Which of the following short circuit is the most dangerous ?
A capacitor start, capacitor run single phase induction motor is basically a
In squirrel cage induction motor, the starting current is
The input gate current of FET is closer to
The magnetising force on an iron ring is 1750 AT/m when the flux density is 1.1 T. The relative permeability of iron is
A 10 mH inductor carries a sinusoidal current of 1A rms at a frequency of 50 Hz. The average power dissipated by the inductor is
Silicon diode is less suited for low voltage rectifier operation because
The resistivity of a semi-conductor
Resistivity of conductors increases with increase in temperature because rate of collisions between free electrons and ions increase with increase of temperature. However, the resistivity of semiconductors decreases with increase in temperature, because more and more covalent bonds are broken at higher temperatures.
In case of induction motor, with increase in supply voltage, which of the following increases?
In case of transformers regulation varies as
In a transformer, with change in frequency
Sometimes a reactor is connected in series with a transformer to
Damping torque in instruments is generally not produced
In hot wire instruments, the sensing wire is made of
When a multiplier is added to an existing voltmeter for extending its range, its electromagnetic damping
In an insulated cable having core diameter d and overall diameter D, the ratio of maximum
to minimum dielectric stress is given by
When the damping force is more than the optimum, the instrument will become
In a moving iron type ammeter, the coil has
How many relays are used to detect inter phase fault of a three line system ?
If δ is the loss angle of the cable, its power factor is
The critical clearing time of a fault in power system is related to
The depletion layer across a p+–n junction lies
A combination of two diodes connected in parallel when compared to a single diode can with stand
In a separately excited generator, field winding is excited by
In an RLC parallel circuit, the impedance at resonance is
Which one of the following theorem is a manifestation of the law of conservation of energy ?
Resistivity of earth increases sharply if the moisture falls below
Which type of drive can be used for hoisting machinery