HPCL - Electrical & Electronics Engineering Questions for Placement

HPCL – Electrical & Electronics Engineering Questions for Placement

Complete the following statement:

• Space charge region around a p – n junction

a. Contains one type of mobile carriers depending on the level of doping of the p or n regions
b. Does not contain mobile barriers
c. Contains electrons only as free carriers
d. Contains both free electrons and holes

• What will be the consequences, if you remove the bypass capacitor across the emitter – leg resistor in a CE amplifier?

a. Decrease in voltage gain
b. Increase in current gain
c. Increase in voltage gain
d. Decrease in current gain

• On what does the frequency of the ripple in the output voltage of a 3 – phase semi - converter depends upon?

a. Firing angle and supply frequency
b. Firing angle and load resistance
c. Only on load circuit parameters
d. Firing angle and load inductance

• Which oscillator comprises of the highly stable resonance characteristic?

a. Colpitts
b. Hartley
c. Weinbridge
d. Crystal

• ISDN handles data pertaining to

a. Computer data only
b. All digital services
c. Speech only
d. Speech and video

• Which converter can operate in both 3 and 6 pulse modes?

a. 3 phase full converter
b. 1 phase full converter
c. 3 phase half wave converter
d. 3 phase semi – converter

• When do you use analog data acquisition system?

a. Narrow bandwidth and high accuracy are required
b. Wide bandwidth and low accuracy are required/sufficient
c. Wide bandwidth and high accuracy are required
d. Narrow bandwidth and low accuracy are required/ sufficient

• With which of the option can you carry out the measurement of frequency?

a. Wien’s bridge
b. Owen’s bridge
c. Schering’s bridge
d. Maxwell’s inductance – capacitance bridge

• What will be the minimum number of line currents when the total number of branches in a network is = b and the graph of the network has ‘n’ number of branches?

a. b – n
b. n
c. b
d. b + n

• The equation of continuity defines the relation between:

a. flux density and charge density
b. electric field and magnetic field
c. current density and charge density
d. electric field and charge density

• The E and H vector fields in a travelling electromagnetic wave are:

a. Parallel in space
b. Perpendicular in space
c. H is in the direction of wave travel
d. E is in the direction of wave travel

• What will be the dominant cut off wavelength if for a rectangular wave guide 2.5cm * 1.2cm?

a. 2.4 cm
b. 5 cm
c. 3.7 cm
d. 2.5 cm

• The device used for providing rate feedback in position control systems is called:

a. Synchro
b. Servomotor
c. Potentiometer
d. Tachogenerator

• What will you use to eliminate Harmonics?

a. Short pitch winding
b. Skewing of rotor
c. Distribution winding
d. All of the above

• What is the temperature of electrode in Arc furnace?

a. 1500 degree
b. 4500 degree
c. 1000 degree
d. 1500 to 3500 degree

• Which of the element retains its energy after its source is disconnected?

a. Capacitor
b. Resister
c. Thermistor
d. Inductor

• What does a sine wave generates when given as an input to Schmitt trigger?

a. Saw tooth wave
b. Sine wave
c. Square wave
d. Triangle wave

• What does Hays Bridge and Schering Bridge used to measure?

a. Capacitance, Inductance
b. Inductance, Inductance
c. Resistance, Capacitance
d. Inductance, Capacitance

• What will be the power factor if the two watts meters measurement’s reading ratio is –(1-sqrt3):(1+sqrt3)?

a. 0
b. 1
c. 0.866
d. 0.707

• Choose which transistor mode gives the inverted output?

a. Common collector
b. Common base
c. Common emitter
d. None of the above


• What are the elements in the circuit when V=100sin (1000t+46 deg), I=2Sin (1000t+80 deg)?

a. R=40 ohm, L=30mH
b. R=40 ohm, L=33.3 micro farads
c. R=30 ohm, C=33.3 micro farads
d. R=30 ohm, L=30mH

• What is the function of a closed loop transfer when G(s) = (1-s)/s(s+2)?

a. Marginally stable
b. Stable
c. Unstable
d. All of the above

• How can you improve the stability of transient?

a. Auto re-closers
b. By putting series capacitor
c. By using dynamic resister
d. All of the above

• What material is generally used while making power diode?

a. Germanium
b. Silicon
c. Both
d. None of the above

• In which mode will you find the diode when both the junction of NPN diode is reverse biased?

a. Cut-off
b. Inverted
c. Active
d. Saturation

• Convert the 101101 Binary number into Octal number.

a. 51
b. 65
c. 45
d. 55

• In which band does the free electron exist?

a. 2
b. 3
c. 1
d. Conduction band


• What is the efficiency of half wave rectifier?

a. 50%
b. 100%
c. 45%
d. 86%

• What will be the value of Acm when CMRR of an OP AMP is given as 80db and Ad is 20000?

a. 2
b. 8
c. 4
d. 1

• Choose which of the below mentioned stands true for its justification.

a. A transparent latch consists of a D – flip flop
b. A flip – flop is used to store 1 – bit of information
c. Master slave flip flop is used to store 2 bits of information
d. Race around condition occurs in JK flip flop when both the inputs are 1

• Choose the correct option to identify the fastest read/writable memory?
a. Flash
b. PROM
c. EEPROM
d. None of the above

• Which logic is used by odd parity generator?

a. Analog
b. Sequential
c. Digital
d. None of the above

• If you have to implement AB+CD+EF, how many NAND gates will be required to do so?

a. 2
b. 1
c. 3
d. 4

• State the value of A’+1.

a. 1
b. A
c. A’
d. None of the above


• According to Boolean Algebra what is the value of 1+A+B+C

a. A+B+C
b. 1
c. A
d. None of the above

• How many number of 1’s are there in the binary expression – 162*9+162*7+16*5+3?

a. 23
b. 4
c. 6
d. 10

• Choose the correct alternative that is used as a data selector.

a. Decoder
b. Modulator
c. Encoder
d. Demodulator

• Which transistor will you use in enhancement mode?

a. UJT
b. MOSFET
c. JFET
d. NPN

• Which of the following option consist of high cut – off frequency?

a. CE
b. CB
c. CC
d. None of the above

• What is the largest negative number be represented with 8 bits in 2’s compliment representation?

a. -127
b. -256
c. -255
d. -128

• State the range of generation voltage.

a. Between 400 KV and 700 KV
b. Between 11 KV and 33 KV
c. Between 132 KV and 400 KV
d. None of the above

• Choose which of the following option falls true for hysteresis motor.

a. Needs Dc excitation
b. Is not a self – starting motor
c. Is a constant speed motor
d. Cannot be run in reverse speed

• Which heating method is independent of supply frequency?

a. Dielectric heating
b. Electric arc heating
c. Induction heating
d. Electric resistance heating

• What is the power factor of a squirrel cage induction motor?

a. Low at heavy load only
b. Low at light load only
c. Low at light and heavy load only
d. Low at rated load only

• Choose the correct option which uses direct inward dialling as one of its feature.

a. VPN
b. PBX
c. PSTN
d. EPABX

• Choose the correct option for identifying the two windings of a transformer?

a. Not linked at all
b. Conductively linked
c. Electrically linked
d. Inductively linked

Fill in the blanks

• In a stepper motor the angular displacement _______

a. It cannot be used for positioning of work tables and tools in NC machine
b. Can be precisely controlled
c. It cannot be readily interfaced with micro - computer based controller
d. The angular displacement cannot be precisely controlled

• The purpose of inducing emf in the primary of a transformer ______

a. Leads the flux by 90 degree
b. Lags behind the flux by 90 degree
c. Is in phase with the flux
d. Is in phase opposition to that of flux

• Which motor will you choose which can operate in both lagging as well as leading power factors?

a. Synchronous motor
b. Squirrel cage motor
c. DC shunt motor
d. Wound rotor induction motor

• What will be the voltage regulation of a full load and 0.80 power factor lagging load transformer when a two winding single phase transformer has a voltage regulation of 4.5% at full load and unity power factor?

a. 4.5% or more
b. Less that 4.5%
c. 4.5%
d. More than 4.5 %

• What is the armature mmf in a D.C machine?

a. Rotating w.r.t field
b. Stationary w.r.t armature
c. Rotating w.r.t brushes
d. Stationary w.r.t field

• What will be the output of a step – input is given to an op – amp integrator?

a. Rectangular wave
b. A ramp
c. A sinusoidal wave
d. A triangular wave with DC bias

• What will be the output voltage of a transformer if it is primarily energised from a square wave voltage source?

a. A pulse wave
b. A square wave
c. A sine wave
d. A triangular wave

• How will a motor react if salient pole is running synchronously at no load and its field current is switched off?

a. Come to a halt
b. Continue to run at a speed slightly less than the synchronous speed
c. Continue to run at synchronous speed
d. Continue to run at a speed slightly more than the synchronous speed

• Why should you always start the D.C series motor with load?

a. It will fail to start
b. It will not develop high starting torque
c. At no load, it will rotate at dangerously high speed
d. All the above mentioned are true

• Which is the most suitable servomotor for low power application?

a. A DC shunt motor
b. A DC series motor
c. An AC two – phase induction motor
d. An AC series motor

• What will you use to take out the current from the stator of an alternator?

a. Commutator segments
b. Slip rings
c. Carbon brushes
d. Solid connections

• When will be the voltage zero in a transformer?

a. Leading p.f
b. Zero p.f leading
c. Unity p.f
d. Lagging p.f

• In audio amplification, which distortion will you least object?

a. Frequency
b. Harmonic
c. Intermediation
d. Phase

• When the relative speed between the magnetic fields of stator and rotor does is zero under steady state operation?

a. Synchronous machine
b. DC machine
c. Single phase induction machine
d. 3 phase induction machine
e. All of the above are true

• What shall be the secondary output voltage if the primary winding of a 220/6V, 50 Hz transformer is energised by a 110V, 60 Hz supply?

a. 3.0 V
b. 3.6 V
c. 2.5 V
d. 6.0 V

• Choose the correct option to identify whose protection is taken care by ‘who relay’?

a. Long lines only
b. Short lines only
c. Any line
d. Medium lines only

• What is the mechanical power developed in terms of air gap power Pg in a 3 phase induction motor running at slip ‘s’?

a. (s-1) Pg
b. Pg/1-S
c. 1-SPg-Answer
d. S.Pg

• The electromagnetic torque developed in proportional to what in a D.C series motor?

a. 1a
b. 12a-Answer
c. 1/1a
d. 1/12a

• What is the frequency of the rotor current in a 3 phase 50 Hz, 4 pole induction motor at full load?

a. 2 Hz
b. 20 Hz
c. Zero
d. 50 Hz

• What does the damper winding produce when a synchronous motor is running at a synchronous speed?

a. Eddy current torque
b. Damping torque
c. No torque
d. Torque aiding the developed torque

• What is the unit of magnetic flux density?

a. Bohr
b. Weber/sec
c. Gauss
d. Tesla

• Define bistable multi – vibrator.

a. Saw tooth wave generator
b. Free running oscillator
c. Crustal oscillator
d. Triggered oscillator

• Choose the correct mean by which the speed and torque of induction motor can be varied?

a. Frequency control
b. Stator voltage control
c. Rotor voltage control
d. All of the above