Optoelectronics, Power electronics, Electromechanical systems

Optoelectronics, Power electronics, Electromechanical systems - Electronics Engineering test questions

(1) Radiometric systems deals with

(A) All electromagnetic energy
(B) Only gamma rays, X-rays and microwaves
(C) Only AM, FM and TV electromagnetic energy
(D) Only visible light

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(2) The human eye responds to wavelengths of electromagnetic energy that are in the range of

(A) 10000 Å and above
(B) 4000 Å to 7700 Å
(C) 300 Å to 3000 Å
(D) 7700 Å to 10000 Å

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(3) A source of light produces discrete bundles of energy, which is called

(A) Electrons
(B) Photons
(C) Neutrons
(D) Ions

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(4) The one, which is not classified as a photoconductive device is

(A) A PIN photo diode
(B) A light dependent register
(C) A photo transistor
(D) A photo voltaic cell

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(5) What will be the forward voltage of a GaAs LED under normal operating conditions?
(A) 0 to 1 V
(B) 5.1 to 7.1
(C) 1.1 to 3 V
(D) 3.1 to 5 V

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(6) As sun’s radiation falls on a solar cell, the short circuit current or open circuit voltage is produced because

(A) Minority carriers flow across the junction
(B) Majority carriers flow across the junction
(C) Depletion layer gets reduced
(D) Carrier recombination takes place near the junction

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(7) In a solar cell, the value of open circuit voltage is

(A) 100 mV
(B) 0.5 mV
(C) 1 mV
(D) 10 mV

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(8) At what interval 6 SCR’s in a 3 Φ full converter are fired?

(A) 180 °
(B) 120 °
(C) 60 °
(D) 0 °

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(9) What is the PIV rating of each diode in a 3 Φ half wave rectifier circuit?

(A) 2 Vm
(B) Vm
(C) √2 Vm
(D) √3 Vm

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(10) What will happen if the firing angle in a SCR rectifier is decreased?

(A) Output is increased
(B) Output is decreased
(C) Output is maximum
(D) Output is unaffected

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(11) Consider a single-phase semiconductor. For continuous conduction, free wheeling diode conducts for

(A) α
(B) π
(C) π + α
(D) π - α

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(12) What will be the output voltage of a step up chopper circuit if Vs is the source voltage and a is the duty cycle?

(A) Vs (1 + α)
(B) Vs (1 – α)
(C) Vs / 1 - α
(D) Vs / 1 + α

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(13) In series connected thyristors,

(A) L and C is used to filter out the ripple
(B) R, C is called snubber circuit
(C) L is used to increase di/dt at switch on
(D) L is used for tuning out junction capacitance

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(14) For controlling the speed of which type of motors the ward Leonard system is used?

(A) Three phase motors
(B) Universal motors
(C) Single phase ac motors
(D) DC motors

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(15) RC snubber circuit is used to limit the rate of

(A) Rise of voltage across SCR
(B) Rise of current in SCR
(C) Conduction period
(D) All of the above

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(16) Consider a thyristor controlled half wave rectifier. Voltage source = 200 sin 314t, resistive load = 50 Ω, Firing angle = 30 ° with respect to the supply voltage waveform. Average power in the load =?

(A) 80.6 W
(B) 60.6 W
(C) 70.6 W
(D) 90.6 W

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(17) Chopper control for DC motor provides variation in

(A) Frequency
(B) Input voltage
(C) Current
(D) Output voltage

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(18) Consider a single phase AC regulator with an inductance load. Source voltage = 230 V at frequency = 50 Hz and ω L = 5 ohms. The control range of firing angle is

(A) π > a > π /2
(B) 0 < a < π /2
(C) 0 < a < π
(D) π /2 = a = π

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(19) Which of the following is a thyristor equivalent of a thyratron tube?

(A) SCR
(B) Diac
(C) Triac
(D) None of the above

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(20) For a six phase half wave rectifier input is 220 V, 60 Hz. The triple frequency is

(A) 720 Hz
(B) 60 Hz
(C) 360 Hz
(D) 500 Hz

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(21) During induction heating, the skin depth of penetration is proportional to

(A) 1 / √frequency
(B) Frequency
(C) Frequency^²
(D) Frequency

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(22) In a three-phase half wave rectifier, each diode conducts for a duration of
(A) 60°
(B) 120°
(C) 180°
(D) 90°

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(23) Which one of the following device cannot be triggered with voltage of either polarity?

(A) Diac
(B) SCS
(C) Triac
(D) All of the above

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(24) In a pulse triggering system for thyristor the minimum duration of pulse should be at least

(A) 10 ms
(B) 30 ms
(C) 10 μs
(D) 1 sec

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(25) The angle of conduction in a thyristor circuit, is changed by changing

(A) Forward current
(B) Anode voltage
(C) Anode current
(D) Gate current

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(26) The holding current is __________ than latching current

(A) Less
(B) More
(C) Equal
(D) None of the above

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(27) What is used to improve lateral stability?

(A) A high aspect ratio
(B) Dihedral
(C) Offsetting the vertical fin
(D) Balanced control

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(28) The right-of-way on final approach for landing is normally given to

(A) Airplanes at lower altitude
(B) Airplanes at higher altitude
(C) Faster airplanes
(D) Slower airplanes

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(29) When an aircraft is suffering communication failure, it may alert ATC to the problem by selecting the code

(A) 6400
(B) 6700
(C) 7700
(D) 7600

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(30) When a pilot is flying VFR in an uncontrolled airspace, he should monitor
(A) 122.2 MHz
(B) 123.2 MHz
(C) 126.7 MHz
(D) 121.5 MHz

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(31) Let us consider a case where your heading is 180° and the ADF is 90°. If you turn to magnetic heading of 150°, the ADF will read

(A) 120°
(B) 240°
(C) 360°
(D) 160°

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(32) To indicate whether the glass has slipped, the marking on an instrument used is
(A) Red radial line
(B) White index mark
(C) Blue index mark
(D) None of the above

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(33) The fixed reference marker attached to the compass bowl of the magnetic compass is called

(A) Lubber line
(B) Pole line
(C) Reeder line
(D) Card line

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(34) The main reason to use integral fuel tank in many large aircraft is because they

(A) Facilitate servicing
(B) Minimize leakage
(C) Reduce fire hazards
(D) Reduce weight

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(35) In an electro mechanical autopilot system, the component that is used as a sensing device is

(A) Controller
(B) Gyro
(C) Servo
(D) Turn and back

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(36) In overcoming the effect of armature reaction, the method most commonly used is

(A) Through the use of ALNICO field pieces
(B) Through the use of shaded poles
(C) Through the use of Interpoles
(D) None of the above

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(37) A starter generator during flight operation is to be cooled by

(A) An integral fan and ram air
(B) An external motor driven fan
(C) Engine bleed air
(D) The environment system cooled air

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(38) To measure radio frequency alternating current, the type of ammeter used is
(A) Half wave bridge type
(B) Full wave bridge type
(C) Emitter base type
(D) Thermo couple type


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(39) The electric circuits can be protected from overheating by the use of

(A) Thermocouple
(B) Shunts
(C) Fuses
(D) Solenoids

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(40) The basic difference between an autosyn and magnesyn indicating system is

(A) Rotor
(B) Transmitter
(C) Receiver
(D) Winding

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(41) In most of the aircraft the basic meter used to indicate cylinder head temperature is

(A) Electro dynamometer
(B) Galvanometer
(C) Iron-vane meter
(D) Thermo couple type meter

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(42) The primary engine instrument is

(A) Fuel flow meter
(B) Air speed indicator
(C) Torque meter
(D) Tachometer

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