EE and Elecs Objective - PEJ
The speed of a DC shunt motor at no-load is ____________ higher than its speed at rated load. A. 5 to 10% B. 15 to 20% C. 25 to 30% D. 35 to 40%
A. 5 to 10%
Low head plants generally use A. Pelton Turbines B. Francis Turbine C. Pelton or Francis Turbine D. Kaplan Turbines
A. Pelton Turbines
When a step-input is given to an op-amp integrator, the output will be A. a ramp B. a sinusoidal wave C. a rectangular wave D. a triangular wave with DC bias
A. a ramp
If a transformer primary is energized from a square wave voltage source, its output voltage will be A. a square wave B. a sine wave C. a triangular wave D. a pulse wave
A. a square wave
The DC series motor should always be started with load because A. at no load, it will rotate at dangerously high speed B. it will fail to start C. it will not develop high starting torque D. all is true
A. at no load, it will rotate at dangerously high speed
The breakdown mechanism in a lightly doped p-n junction under reverse biased condition is called A. avalanche breakdown B. zener breakdown C. breakdown by tunneling D. high voltage breakdown
A. avalanche breakdown
The generation voltage is usually A. between 11 KV and 33 KV B. between 132 KV and 400 KV C. between 400 KV and 700 KV D. none of the above
A. between 11 KV and 33 KV
A 220/440 V, 50 Hz, 5 KVA, single phase transformer operates on 220V, 40Hz supply with secondary winding open circuited. Then A. both eddy current and hysteresis losses decreases B. both eddy current and hysteresis losses increases C. eddy current loss remains the same but hysteresis loss increases D. eddy current loss increases but hysteresis loss remains the same
A. both eddy current and hysteresis losses decreases
In a stepper motor the angular displacement A. can be precisely controlled B. it cannot be readily interfaced with microcomputer based controller C. the angular displacement cannot be precisely controlled D. it cannot be used for positioning of work tables and tools in NC machines
A. can be precisely controlled
A single phase Hysteresis motor A. can run at synchronous speed only B. can run at sub synchronous speed only C. can run at synchronous and super synchronous speed D. can run at synchronous and sub synchronous speed
A. can run at synchronous speed only
The efficiency of a transformer is mainly dependent on A. core losses B. copper losses C. stray losses D. dielectric losses
A. core losses
Space charge region around a p-n junction A. does not contain mobile carriers B. contains both free electrons and holes C. contains one type of mobile carriers depending on the level of doping of the p or n regions D. contains electrons only as free carriers
A. does not contain mobile carriers
The reverse - saturation current of a silicon diode A. doubles for every 10°C increase in temperature B. does not change with temperature C. halves for every 1°C decrease in temperature D. increases by 1.5 times for every 2°C increment in temperature
A. doubles for every 10°C increase in temperature
The armature of a dc machine is laminated to reduce: A. eddy current loss B. hysteresis loss C. copper losses D. friction and windage losses
A. eddy current loss
To achieve low PT error, the burden value should be ____________. A. low B. high C. medium D. none of the above
A. low
The power factor of a squirrel cage induction motor is A. low at light load only B. low at heavy load only C. low at light and heavy load both D. low at rated load only
A. low at light load only
When two transformers are operating in parallel, they will share the load as under: A. proportional to their impedances B. inversely proportional to their impedances C. 50% - 50% D. 25%-75%
A. proportional to their impedances
The 'sheath' is used in cable to A. provide strength to the cable B. provide proper insulation C. prevent the moisture from entering the cable D. avoid chances of rust on strands
A. provide strength to the cable
Two transformers operating in parallel will share the load depending upon their A. rating B. leakage reactance C. efficiency D. per-unit impedance
A. rating
The synchronous reactance of the synchronous machine is ______________. A. ratio between open circuit voltage and short circuit current at constant field current B. ratio between short circuit voltage and open circuit current at constant field current C. ratio between open circuit voltage and short circuit current at different field current D. ratio between short circuit voltage and open circuit current at different field current
A. ratio between open circuit voltage and short circuit current at constant field current
The direction of rotation of hysteresis motor is reversed by A. shift shaded pole with respect to main pole B. reversing supply lead C. either A or B D. neither A nor B
A. shift shaded pole with respect to main pole
The size of the feeder is determined primarily by A. the current it is required to carry B. the percent variation of voltage in the feeder C. the voltage across the feeder D. the distance of transmission
A. the current it is required to carry
At present level of technology, which of the following method of generating electric power from sea is most advantageous? A. tidal power B. ocean thermal energy conversion C. ocean currents D. wave power
A. tidal power
The speed-torque characteristics of a DC series motor are approximately similar to those of the _________motor. A. universal B. synchronous C. DC shunt D. two-phase
A. universal
In a CE-connected transistor amplifier with voltage-gain A , the capacitance C_bc is amplified by a factor A. A_v B. 1 + A_v C. sq. rt. of (1 + A_v) D. (A_V)^2
B. 1 + A_v
For an op-amp having differential gain A and common-mode gain Ac the CMRR is given by A. A_v+ A_c B. A_v / A_c C. (A_v / A_c) + 1 D. A_c / A_v
B. A_v / A_c
In a DC series motor the electromagnetic torque developed is proportional to A. Ia B. Ia^2 C. 1/Ia D. 1/Ia^2
B. Ia^2
For a line voltage V and regulation of a transmission line R A. R α V B. R α (1/V) C. R α V^2 D. R α (1/V^2)
B. R α (1/V)
The most suitable servomotor for low power applications is A. a DC series motor B. a DC shunt motor C. an AC two-phase induction motor D. an AC series motor
B. a DC shunt motor
Regenerative braking A. can be used for stopping a motor B. cannot be easily applied to DC series motors C. can be easily applied to DC shunt motors D. cannot be used when motor load has overhauling characteristics
B. cannot be easily applied to DC series motors
A salient pole synchronous motor is running at no load. Its field current is switched off. The motor will A. come to stop B. continue to run at synchronous speed C. continue to run at a speed slightly more than the synchronous speed D. continue to run at a speed slightly less than the synchronous speed
B. continue to run at synchronous speed
Inverse definite minimum time lag relay is also called ___________. A. pilot relay B. differential relay C. over current relay D. directional overcurrent relay
B. differential relay
Electric resistance seam welding uses __________ electrodes. A. pointed B. disc C. flat D. domed
B. disc
In a three phase induction motor the maximum torque A. is proportional to rotor resistance r2 B. does not depend on r2 C. is proportional to sq. rt of r2 D. is proportional to r2^2
B. does not depend on r2
The important characteristic of emitter-follower is A. high input impedance and high output impedance B. high input impedance and low output impedance C. low input impedance and low output impedance D. low input impedance and high output impedance
B. high input impedance and low output impedance
In a capacitor start single-phase induction motor, the capacitor is connected A. in series with main winding B. in series with auxiliary winding C. in series with both the windings D. in parallel with auxiliary winding
B. in series with auxiliary winding
The two windings of a transformer is A. conductively linked B. inductively linked C. not linked at all D. electrically linked
B. inductively linked
A hysteresis motor A. is not a self-starting motor B. is a constant speed motor C. needs dc excitation D. cannot be run in reverse speed
B. is a constant speed motor
If the field circuits of an unloaded salient pole synchronous motor gets suddenly open circuited, then A. the motor stops B. it continues to run at the same speed C. it runs at the slower speed D. it runs at a very high speed
B. it continues to run at the same speed
No load current in a transformer: A. lags the applied voltage by 90° B. lags the applied voltage by somewhat less than 90° C. leads the applied voltage by 90° D. leads the applied voltage by somewhat less than 90°
B. lags the applied voltage by somewhat less than 90°
In a transformer the voltage regulation will be zero when it operates at A. unity p.f. B. leading p.f. C. lagging p.f. D. zero p.f. leading
B. leading p.f.
An alternator is delivering rated current at rated voltage and 0.8 power-factor lagging case. If it is required to deliver rated current at rated voltage and 0.8 power-factor leading, the required excitation will be A. less B. more C. more or less D. the same
B. more
The resistance representing mechanical output in the equivalent circuit of an induction motor as seen from the stator is: A. (r2)'[(1/s) - 1] B. (r2)'/s C. r2^2[(1/s) - 1] D. r2/s
A. (r2)'[(1/s) - 1]
In a full-wave rectifier without filter, the ripple factor is A. 0.482 B. 1.21 C. 1.79 D. 2.05
A. 0.482
The maximum power for a given excitation in a synchronous motor is developed when the power angle is equal to A. 0o B. 45o C. 60o D. 90o
A. 0o
The value of ripple factor of a half-wave rectifier without filter is approximately A. 1.2 B. 0.2 C. 2.2 D. 2.0
A. 1.2
Which of the following may be value of resistivity of copper? A. 1.7 X 10-6 B. 1.7 X 10-5 C. 1.7 X 10-4 D. 1.7 X 10-3
A. 1.7 X 10-6
Wien bridge oscillator can typically generate frequencies in the range of A. 1KHz - 1MHz B. 1 MHz - 10MHz C. 10MHz - 100MHz D. 100MHz - 150MHz
A. 1KHz - 1MHz
The line trap unit employed in carrier current relaying: A. offers high impedance to 50 Hz power frequency signal B. offers high impedance to carrier frequency signal C. offers low impedance to carrier frequency signal D. both A & C
B. offers high impedance to carrier frequency signal
The control terminal (pin5) of 555 timer IC is normally connected to ground through a capacitor (~0.01μF). This is to A. protect the IC from inadvertent application of high voltage B. prevent false triggering by noise coupled onto the pin C. convert the trigger input to sharp pulse by differentiation D. suppress any negative triggering pulse
B. prevent false triggering by noise coupled onto the pin
The boundary of the protective zone is determined by the A. location of CT B. sensitivity of relay used C. location of PT D. none of these
B. sensitivity of relay used
In class-A amplifier, the output current flows for A. a part of the cycle or the input signal B. the full cycle of the input signal C. half the cycle of the input signal D. 3/4th of the cycle of the input signal
B. the full cycle of the input signal
If the voltage is reduced to half, the torque developed by an induction motor will be reduced to A. ¼ of original torque B. ½ of original torque C. 1/8 of original torque D. 1/16 of original torque
B. ½ of original torque
In a DC shunt motor the terminal voltage is halved while the torque is kept constant. The resulting approximate variation in speed 'ω' and armature current ' Ia ' will be A. Both ω and Ia are doubled B. ω is constant and Ia is doubled C. ω is doubled while Ia is halved D. ω is constant but Ia is halved
B. ω is constant and Ia is doubled
In a three phase induction motor running at slip 's' the mechanical power developed in terms of air gap power Pg is A. (s-1)Pg B. Pg/(1-s) C. (1-s)Pg D. (s)(Pg)
C. (1-s)Pg
The open-loop gain of an op-amp available in the market may be around. A. 10^-1 B. 10 C. 10^5 D. 10^2
C. 10^5
Mass of a proton is how many times greater than mass of an electron A. 184000 B. 18400 C. 1840 D. 184
C. 1840
If the phase angle of the voltage coil of a directional relay is 50o, the maximum torque angle of the relay is A. 130o B. 100o C. 50o D. 25o
C. 50o
The minimum number of flip-flops required to construct a mod-75 counter is A. 5 B. 6 C. 7 D. 8
C. 7
In a salient pole synchronous machine (usual symbols are used): A. Xq > Xd B. Xq = Xd C. Xq < Xd D. Xq = 0
C. Xq < Xd
A synchro has A. a three phase winding on rotor and a single-phase winding on stator B. a three phase winding on stator and a commutator winding on rotor C. a three phase winding on stator and a single-phase winding on rotor D. a single-phase winding on stator and a commutator winding on rotor
C. a three phase winding on stator and a single-phase winding on rotor
The torque-speed characteristics of an AC operated universal motor have ______ characteristic and it______ be started under no-load condition. A. an inverse, can B. a nearly inverse, can C. an inverse, cannot D. a nearly inverse, cannot
C. an inverse, cannot
In case of a universal motor, torque pulsation is minimized by _________. A. load inertia B. rotor inertia C. both rotor and load inertia D. none of the above
C. both rotor and load inertia
Electric ovens using heating elements of _______________ can produce temperature up to 3000°C. A. nickel B. graphite C. chromium D. iron
C. chromium
In an intrinsic semiconductor, the Fermi-level is A. closer to the valence band B. midway between conduction and valence band C. closer to the conduction band D. within the valence band
C. closer to the conduction band
A commutator in a DC machine A. reduces power loss in armature B. reduces power loss in field circuit C. converts the induced AC armature voltage into direct voltage D. is not necessary
C. converts the induced AC armature voltage into direct voltage
The size of a conductor used in power cables depends on the A. operating voltage B. power factor C. current to be carried D. type of insulation used
C. current to be carried
As the voltage of transmission increases, the volume of conductor A. increases B. does not change C. decreases D. increases proportionately
C. decreases
In a three phase transformer, if the primary side is connected in star and secondary side is connected in delta, what is the angle difference between phase voltages in the two cases? A. delta side lags by -30° B. star side lags by -30° C. delta side leads by 30° D. star side leads by -30°
C. delta side leads by 30°
Removing bypass capacitor across the emitter leg resistor in a CE amplifier causes A. increase in current gain B. decrease in current gain C. increase in voltage gain D. decrease in voltage gain
D. decrease in voltage gain
Hysteresis is desirable in Schmitt-trigger, because A. energy is to be stored/discharged in parasitic capacitances B. effects of temperature would be compensated C. devices in the circuit should be allowed time for saturation and desaturation D. it would prevent noise from causing false triggering
C. devices in the circuit should be allowed time for saturation and desaturation
Out of the following methods of heating the one which is independent of supply frequency is A. electric arc heating B. induction heating C. electric resistance heating D. dielectric heating
C. electric resistance heating
The common collector amplifier is also known as A. collector follower B. base follower C. emitter follower D. source follower
C. emitter follower
The EMF induced in the primary of a transformer A. is in phase with the flux B. lags behind the flux by 90 degree C. leads the flux by 90 degree D. is in phase opposition to that of flux
C. leads the flux by 90 degree
In order to reduce the harmful effects of harmonics on the AC side of a high voltage DC transmission system ______are provided. A. synchronous condensers B. shunt capacitors C. shunt filters D. static compensators
C. shunt filters
For LV applications (below 1 kV), ______________ cables are used. A. paper insulated B. plastic C. single core cables D. oil filled
C. single core cables
The current from the stator of an alternator is taken out to the external load circuit through A. slip rings B. commutator segments C. solid connections D. carbon brushes
C. solid connections
Reduction in the capacitance of capacitor-start motor, results in reduced A. noise B. speed C. starting torque D. armature reaction
C. starting torque
In a DC machine, the armature MMF is A. stationary w.r.t. armature B. rotating w.r.t. field C. stationary w.r.t. field D. rotating w.r.t. brushes
C. stationary w.r.t. field
A motor which can conveniently be operated at lagging as well as leading power factors is the A. squirrel cage induction motor B. wound rotor induction motor C. synchronous motor D. DC shunt motor
C. synchronous motor
A differential amplifier, amplifies A. and mathematically differentiates the average of the voltages on the two input lines B. and differentiates the input waveform on one line when the other line is grounded C. the difference of voltages between the two input lines D. and differentiates the sum of the two input waveforms
C. the difference of voltages between the two input lines
In a JFET, at pinch-off voltage applied on the gate A. the drain current becomes almost zero B. the drain current begins to decrease C. the drain current is almost at saturation value. D. the drain-to-source voltage is close to zero volts
C. the drain current is almost at saturation value.
For a large values of |VDS|, a FET behaves as A. voltage controlled resistor B. current controlled current source C. voltage controlled current source D. current controlled resistor
C. voltage controlled current source
Oil-filled cable has a working stress of __________ kV/mm. A. 10 B. 12 C. 13 D. 15
D. 15
The maximum power in cylindrical and salient pole machines is obtained respectively at load angles of A. 90o, 90o B. < 90o, 90o C. 90o, > 90o D. 90o, < 90o
D. 90o, < 90o
In an amplifier with negative feedback A. only the gain of the amplifier is affected B. only the gain and bandwidth of the amplifier are affected C. only the input and output impedances are affected D. All of the four parameters mentioned above would be affected
D. All of the four parameters mentioned above would be affected
The torque, in a _____________is proportional to the square of the armature current A. DC shunt motor B. stepper motor C. two phase servomotor D. DC series motor
D. DC series motor
The introduction of inter poles in between the main pole improves the performance of DC machines, because A. the inter pole produces additional flux to augment the developed torque. B. the flux waveform is improved with reduction in harmonics. C. the inequality of air flux on the top and bottom halves of armature is removed. D. a counter EMF is induced in the coil undergoing commutation.
D. a counter EMF is induced in the coil undergoing commutation.
An AC tachometer is just ________with one phase excited from the carrier frequency. A. a two-phase AC servomotor B. a two-phase induction motor C. an AC operated universal motor D. a hybrid stepper motor
D. a hybrid stepper motor
A stepper motor is A. a DC motor B. a single-phase ac motor C. a multi-phase motor D. a two phase motor
D. a two phase motor
The temperature of resistance furnaces can be controlled by changing the: A. applied voltage B. number of heating elements C. circuit configuration D. all of the above
D. all of the above
A ceiling fan uses A. split-phase motor B. capacitor start and capacitor run motor C. universal motor D. capacitor start motor
D. capacitor start motor
In the heating process of the ________type a simple method of temperature control is possible by means of a special alloy which loses its magnetic properties at a particular high temperature and regains them when cooled to a temperature below this value. A. indirect induction over B. core type induction furnace C. coreless induction furnace D. high frequency eddy current
D. high frequency eddy current
The fan-out of a MOS-logic gate is higher than that of TTL gates because of its A. low input impedance B. high output impedance C. low output impedance D. high input impedance
D. high input impedance
When an amplifier is provided with current series feedback, its A. input impedance increases and output impedance decreases B. input and output impedances both decrease C. input impedance decreases and output impedance increases D. input and output impedances both increase
D. input and output impedances both increase
As compared to shunt and compound DC motors, the series DC motor will have the highest torque because of its comparatively ____________ at the start. A. lower armature resistance B. stronger series field C. fewer series turns D. larger armature current
D. larger armature current
In DC generators, armature reaction is produced actually by A. its field current B. armature conductors C. field pole winding D. load current in armature
D. load current in armature
When a synchronous motor is running at synchronous speed, the damper winding produces A. damping torque B. eddy current torque C. torque aiding the developed torque D. no torque
D. no torque
In a three phase synchronous motor A. the speed of stator MMF is always more than that of rotor MMF B. the speed of stator MMF is always less than that of rotor MMF C. the speed of stator MMF is synchronous speed while that of rotor MMF is zero D. rotor and stator MMF are stationary with respect to each other
D. rotor and stator MMF are stationary with respect to each other
The drive motor used in a mixer-grinder is a A. DC motor B. induction motor C. synchronous motor D. universal motor
D. universal motor