Mock Test on Diploma Electrical Engineering

1. Which of the following has the longest wavelength?
(a) HF
(b) VHF
(c) UHF
(d) SHF

2. A power chopper converts
(a) a.c. to .d.c
(b) d.c. to d.c.
(c) d.c. to a.c.
(d) a.c. to a.c.

3. A thyristor controlled reactor is used to get
(a) variable resistance
(b) variable capacitance
(c) variable inductance
(d) improved reactive power factor

4. The majority carriers in the emitter of a PNP transistor
(a) Holes
(b) Electrons
(c) Atom
(d) molecule

5. A Z-diode is normally operated in
(a) Forward bias mode
(b) Reverse bias mode
(c) Rectifier mode
(d) Converter mode

6. A common emitter BJT amplifier does
(a) Voltage amplification
(b) Both Voltage and Current amplification
(c) Current amplification
(d) None of these

7. In 8085 name the 16 bit registers
(a) Stack pointer
(b) Register B
(c) Register A
(d) PSW

8. Instruction RET (Return) of a 8085 microprocessor
(a) Stack Pointer and Program counter
(b) Stack Pointer only
(c) Program counter only
(d) Set Interrupt Mask and Acc

9. Instruction CALL of a 8085 microprocessor has
(a) 1 byte
(b) 2 bytes
(c) 4 bytes
(d) 3 bytes

10. The TIMER of PPI 8155 is of
(a) 16 bits
(b) 14 bits
(c) 12 bits
(d) 8 bits

11. Which of the following modulation techniques has got maximum SNR?
(a) AM-SSB
(b) AM-DSB
(c) FM
(d) AM-SC

12. A broadcast AM radio transmitter radiates 125 kW when the modulation percentage is 70. How much of this is carrier power?
(a) » 25 kW
(b) 50 kW
(c) 75 kW
(d) 100 kW

13. One disadvantage of adaptive delta modulation over linear delta modulation is that it
(a) requires more bandwidth
(b) is more vulnerable to channel errors
(c) requires a large number of comparators in the encoder
(d) is not suitable for signals with periodic components

14. An FM wave uses a 2-5 V, 500 Hz modulating frequency and has a modulation index of 50. The deviation is
(a) 500 Hz
(b) 100 Hz
(c) 1250 Hz
(d) 25000 Hz

15. The anode current through a conducting SCR is 10A. If its gate current is made one-fourth, then what will be the anode current?
(a) 0
(b) 5A
(c) 10 A
(d) 20 A

16. AC voltage regulators are widely used in
(a) traction drives
(b) fan drives
(c) synchronous motor drives
(d) slip power recovery scheme of slip-ring induction motor

17. A modern power semiconductor device that combines the characteristics of BJT and MOSFET is
(a) GTO
(b) FCT
(c) IGBT
(d) MCT

18. TRIACS can’t be used in AC voltage regulator for a
(a) resistive load
(b) back emf load
(c) inductive load
(d) resistive inductive load

19. In a self controlled synchronous motor fed from a variable frequency inverter,
(a) the rotor poles invariably have damper windings
(b) there are stability problems
(c) the speed of the rotor decides stator frequency
(d) the frequency of the stator decides the rotor speed

20. The depletion region in an open circuited P-N junction diode contains
(a) Electrons
(b) Holes
(c) Uncovered immobile impurity ions
(d) Neutralised impurity atoms

21. The width of the depletion layer of a junction
(a) Decreases with light doping
(b) Increases with heavy doping
(c) Is independent of applied voltage
(d) Is increased under revered bias

22. A tunnel diode is
(a) A very heavily doped PN junction diode
(b) A high resistivity PN junction diode
(c) A slow switching device
(d) Used with reverse bias

23. A zener diode
(a) Has a high forward voltage rating
(b) Has a sharp breakdown at low reverse voltage
(c) Is useful as an amplifier
(d) Has a negative resistance

24. Which of the following specifications is not correct for a common collector amplifier?
(a) High input impedance
(b) Low output impedance
(c) High voltage gain
(d) High current gain

25. The POS form of expression is suitable for circuit using
(a) XOR
(b) NAND
(c) AND
(d) NOR

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26. An EX-OR gate produces an output only when its two inputs are
(a) Same
(b) Different
(c) High
(d) low

27. A microprocessor contains ROM chip which contain
(a) Control function
(b) Arithmetic function
(c) Instruction to execute data
(d) Memory functions

28. The program counter in a 8085 microprocessor is a 16-bit register, because
(a) It counts 16 bits at a time
(b) There are 16 address lines
(c) It facilities the user storing 16 bit data temporarily
(d) It has to fetch two 8-bit data at a time

29. Output of the assembler in machine code is referred to as
(a) Object program
(b) Source program
(c) Macroinstruction
(d) Symbolic instruction

30. Both the ALU and control section of CPU employ which special purpose storage locations?
(a) Buffers
(b) Decoders
(c) Accumulators
(d) Registers

31. After completing the execution, microprocessor returns to
(a) Halt state
(b) Execute state
(c) Fetch state
(d) Interrupt state

32. Eight memory chips of 32×4 bit size have their address buses connected together. What is the size of this memory system?
(a) 512×2 bits
(b) 256×4 bits
(c) 64×16 bits
(d) 32×32 bits

33. In AM, the carrier is changed by a modulating signal. What parameter of the carrier is changed?
(a) amplitude
(b) frequency
(c) pulse width
(d) phase

34. After firing an SCR, the gate pulse is removed. The current in the SCR will
(a) remain the same
(b) immediately fall to zero
(c) rise up
(d) rise a little and then fall to zero

35. Thyristors connected in series need
(a) static equalizing circuit
(b) dynamic equalizing circuit
(c) both static and dynamic equalizing circuits
(d) none of these

36. Five limb core construction is preferred over three limb construction as in this type of construction:
(a) Hysteresis loss is reduced
(b) Eddy current loss is reduced
(c) Magnetic reluctance of the three phases can be balanced
(d) Copper losses can be reduced

37. The distribution transformer is designed with minimum possible core losses. This is because:
(a) The primary of the distribution transformer is energized for all 24 hours
(b) Iron losses will cause undue heating
(c) Iron losses may cause damage to the insulation
(d) All of these

38. Which of the following transformer connection will give highest secondary voltage:
(a) Delta primary, delta secondary
(b) Delta primary, star secondary
(c) Star primary, delta secondary
(d) Star primary, star secondary

39. Major insulation in a transformer is the insulation between the:
(a) LV wining and core
(b) LV winding and HV winding
(c) Turns of the windings
(d) Both (a) and (b)

40. The transformer oil should have:
(a) High volatility
(b) High viscosity
(c) High dielectric strength
(d) All of these

41. For minimum weight of the transformer, the iron weight should be __ the weight of the copper:
(a) More than
(b) Equal to
(c) Less than
(d) None of these

42. The main purpose of using core in a transformer is to
(a) Decrease iron losses
(b) Prevent eddy current losses
(c) Eliminate magnetic hysteresis losses
(d) Decrease reluctance of the common magnetic circuit

43. Transformer core are laminated in order to
(a) Simplify its construction
(b) Minimise eddy current loss
(c) Reduce cost
(d) Reduce hysteresis loss

44. In an ideal transformer, the no load primary current I0
(a) Lags behind V1 by 90°
(b) Is in phase with V1
(c) Lead V1 by 90°
(d) Lag V1 by 45°

45. A transformer has negative voltage regulation when its load load power factor is
(a) Zero
(b) Unity
(c) Leading
(d) Lagging

46. The main purpose of performing open-circuit test on a transformer is to measure its
(a) Copper loss
(b) Core loss
(c) Efficiency of transformer
(d) Insulation resistance

47. The ordinary efficiency of a given transformer is maximum when
(a) It run at half full load
(b) It run at full load
(c) Its Cu loss equal to Iron loss
(d) It run at 75 % of full load

48. The capacity of cell is measured in
(a) Watt-hour
(b) Watts
(c) Amperes
(d) Ampere-hour

49. The ratio of Ah efficiency to Wh efficiency of lead-acid cell is
(a) Always less than one
(b) Just one
(c) Always greater than one
(d) None of these

50. Trickle charging of a storage battery helps to
(a) Prevent suphation
(b) Keep it fresh and fully charge
(c) Maintain electrolyte level
(d) Increase it reserve capacity.