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HPCL electronics and electrical questions with answers
1. The unit of magnetic flux density is
(A) gauss
(B) tesla
(C) bohr
(D) weber/sec
Ans: (B)
2. The equation of continuity defines the relation between
(A) electric field and magnetic field
(B) electric field and charge density
(C) flux density and charge density
(D) current density and charge density
Ans: (D)
3. The current in a coil changes from 5A to 1A in 0.4 second. The induced voltage is 40 V. The self
inductance in henry is
(A) 1
(B) 2
(C) 4
(D) 10
Ans: (C)
4. The maximum power will be transferred from a voltage source to a load when
(A) the source impedance is half that of the load impedance
(B) the source impedance is equal to that of the load impedance
(C) the source impedance is twice that of the load impedance
(D) both source and load impedances must be zero
Ans: (B)
5. The total number of branches in a network is equal to b. The graph of the network has n number
of branches. The minimum number of line currents is
(A) b+n
(B) b
(C) b-n
(D) n
Ans: (C)
6. In a travelling electromagnetic wave, E and H vector fields are
(A) perpendicular in space .
(B) parallel in space.
(C) E is in the direction of wave travel.
(D) H is in the direction of wave travel.
Ans: C
7. A wave is incident normally on a good conductor. If the frequency of a plane electromagnetic
wave increases four times, the skin depth, will
(A) increase by a factor of 2.
(B) decrease by a factor of 4.
(C) remain the same.
(D) decrease by a factor of 2.
Ans: D
8. A hollow rectangular waveguide acts as a
(A) High pass filter
(B) Low pass filter
(C) Band pass filter
(D) Low frequency radiator
Ans: A
9. Divergence theorem is applicable for
(A) static field only
(B) time varying fields only
(C) both static and time varying fields
(D) electric fields only
Ans: C
10. For a rectangular wave guide, 2.5cm x 1.2cm, dominant cut off wavelength is
(A) 5 cm
(B) 2.5 cm
(C) 2.4 cm
(D) 3.7 cm
Ans: A
11. When a steady current is passed through a ballistic galvanometer, then the deflection will be
(A) maximum
(B) zero
(C) twice the normal value as it depends on Hibbert magnetic standard
(D) None of the above
Ans: (B)
12. The measurement of frequency can be carried out with
(A) Owen’s bridge
(B) Wien’s bridge
(C) Maxwell’s inductance-capacitance bridge
(D) Schering’s bridge
Ans: (B)
13. The following material is not used for making a piezoelectric transducer
(A) Rochelle salt
(B) Barium titanate
(C) Chlorium sulphide
(D) Quartz
Ans: (C)
14The velocity factor of a transmission line
(A) is governed by the relative permittivity of the dielectric.
(B) is governed by the skin effect.
(C) is governed by the temperature.
(D) All of the above.
Ans: A
15. By using feedback in control systems, the sensitivity to parameter variation is improved.This is
achieved at the cost of
(A) stability
(B) loss of system gain
(C) transient response
(D) reliability
Ans: (B)
16. The phase-lead compensation is used to
(A) increase rise time and decrease overshoot.
(B) decrease both rise time and overshoot
(C) increase both rise time and overshoot
(D) decrease rise time and increase overshoot
Ans: (B)
17. In position control systems, the device used for providing rate feedback is called
(A) potentiometer
(B) synchro
(C) tachogenerator
(D) servomotor
Ans: (C)
18. Given a badly underdamped control system, the type of cascade compensator to be used to
improve its damping is
(A) phase-lead
(B) phase-lag
(C) phase-lag-lead
(D) notch filter
Ans: (B)
19. Analog data acquisition systems are used when
(A) wide bandwidth and low accuracy are required/sufficient
(B) narrow bandwidth and low accuracy are required/sufficient
(C) wide bandwidth and high accuracy are required
(D) narrow bandwidth and high accuracy are required
Ans: (A)
20. In a transmission line terminated by characteristic impedance, Zo
(A) There is no reflection of the incident wave.
(B) The reflection is maximum due to termination.
(C) There are a large number of maximum and minimum on the line.
(D) The incident current is zero for any applied signal.
Ans: A