DMRC Electrical Paper

I am very much prepared for DMRC Junior Engineer entrance exam but I am little week in Electical Paper. Can you suggest me some books to clear and prepare DMRC Electrical Paper. I need book that contain the basic notes along with the old question papers.

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[pawan]

I am providing you the sample Electrical Engineering question paper of Delhi Metro Rail Corporation DMRC Ltd

DMRC Exam Electrical Engineering question paper

1. Which one of the following statements is correct?

Digital modulation techniques are used in satellite communication systems since:

(1) They are easier to handle
(2) Large bandwidth utilization is possible
(3) They have a higher spectral efficiency
(4) They are less prone to interference



Answer : They are less prone to interference


2. How many bits are required to encode 32 level PCM:

(1) 6

(2) 5

(3) 4

(4) 3



Answer : 5


3. The noise is more dominant in which of the following:

(1) PAM

(2) PWM

(3) PPM

(4) FSK



Answer : PAM

4. The phase velocity of wave propagating in a hollow metal wave guide is:

(1) Greater than the velocity of the light in free space
(2) Less than the velocity of the light in free space
(3) Equal to the velocity of the light in free space
(4) Equal to the group velocity



Answer : Greater than the velocity of the light in free space


5. The magnitude of the open-circuit and short circuit input impedance of a transmission line are 100 ohm and 25 ohm respectively. The characteristic impedance of line is:

(1) 25 ohm

(2) 50 ohm

(3) 75 ohm

(4) 100 ohm



Answer : 50 ohm

6. The line of sight communication requires transmit and receive antenna to face each other. If the transmit antenna is vertically polarized, for the best reception the receive antenna should be:

(1) Horizontally polarized
(2) Vertically polarized
(3) At 45 with respect to the horizontal polarization
(4) At 45 with respect to the vertical polarization



Answer : Horizontally polarized

7. A network contains linear resistance and ideal voltage source. If the value of all the resistors are doubled, then the voltage across each resistor is:

(1) Halved

(2) Doubled

(3) Increased by four times

(4) Not changed



Answer : Not changed

8.Twelve 1 ohm resistances are used as edge to form a cube. The resistance between two diagonally opposite corners of the cube is:

(1) 5/6 ohm

(2) 1 ohm

(3) 6/5 ohm

(4) 3/2 ohm



Answer : 5/6 ohm

9. An eight bit digital data 10101100 is fed to an ADC. The reference voltage is +10V. The analog output voltage will be:

(1) 1.05V

(2) 6.74V

(3) 10.10V

(4) 5.15V



Answer : 6.74V

10. A series RLC circuit has a resonant frequency of 1 KHz and a quality factor Q = 100. If each of the R,L and C is doubled from its original value, the new Q of the circuit is:

(1) 25

(2) 50

(3) 100

(4) 200



Answer : 200

11. The input to a coherent detector is DSB-SC signal plus noise. The noise at the detector output is:

(1) The in-phase component
(2) The quadrature-component
(3) Zero
(4) The envelope



Answer : Zero


12. Gunn diode is a:

(1) Negative resistance device
(2) Positive resistance device
(3) High noise device
(4) Low frequency device



Answer : Negative resistance device

13. The intrinsic carrier concentration of silicon sample at 300 K is 2.5 1016/m3. If after doping, the number of majority carriers is 5 1020 /m3, the minority carrier density is:

(1) 1.25 1012/m 3

(2) 0.125 1012/m3

(3) 2.5 1020/m3

(4) 0.5 104/m3



Answer : 1.25 1012/m 3

14. The unit of ? H is:

(1) Ampere

(2) Ampere/meter

(3) Ampere/meter2

(4) Ampere-meter



Answer : Ampere/meter2

15. A PIN diode is:

(1) A metal semiconductor point-contact diode
(2) A microwave mixer diode
(3) Often used as a microwave detector
(4) Suitable for use as a microwave switch



Answer : Suitable for use as a microwave switch

16. 11001, 1001 and 111001 correspond to the 2s complement representation of which one of the following sets of number?

(1) 25, 9 and 57 respectively
(2) 6, 6 and 6 respectively
(3) 7, 7 and 7 respectively
(4) 25, 9 and 57 respectively



Answer : 7, 7 and 7 respectively

17. To couple a coaxial line to a parallel wire line, it is best to use a:

(1) A slotted line
(2) Balun
(3) Directional coupler
(4) Quarter wave line transformer



Answer : Balun

18. Which of the following is used extensively where lowest power consumption is necessary?

(1) CMOS

(2) NMOS

(3) PMOS

(4) Any of the abov



Answer : CMOS


19. Reflex klystron is a:

(1) Low power generator

(2) High power oscillator

(3) Low gain amplifier

(4) Not an oscillator



Answer : Low power generator

20. If the radiated power of AM transmitter is 10 KW, the power in the carrier for modulation index of 0.6 is nearly:

(1) 8.24 KW

(2) 9.26 KW

(3) 8.47 KW

(4) 9.6 KW



Answer : 8.47 KW


21. The current through 8 ohms branch is:





(1) 1A

(2) 0.5A

(3) 1.5A

(4) None of these



Answer : 0.5A



22. JFET in properly biased condition acts as a:

(1) Current controlled current source
(2) Voltage controlled voltage source
(3) Voltage controlled current source
(4) Impedance controlled current source



Answer : Voltage controlled current source

23. The circuit shown in figure is best described as a:



(1) Bridge rectifier

(2) Ring modulator

(3) Frequency discriminatory

(4) Voltage doubler



Answer : Voltage doubler


24. Which amplifier will be preferred for highest gain?

(1) Darlington pair
(2) Cascade amplifier
(3) Cascode amplifier
(4) Depends on the circuitry



Answer : Cascode amplifier

25. The Boolean expression for the truth table shown is:





Answer : Option 1

26. Without any additional circuitry, an 8:1 MUX can be used to obtain:

(1) Some but not all Boolean functions of 3 variables
(2) All function of 3 variables but none of 4 variables
(3) All functions of 3 variables and some but not all of 4 variables
(4) All functions of 4 variables



Answer : All functions of 4 variables


27. The resolution of a potentiometer should be:

(1) Zero

(2) Low

(3) High

(4) Infinite



Answer : Infinite

28. Negative feedback in amplifier:

(1) Improves the SNR at input
(2) Improve SNR at output
(3) Reduces distortion
(4) Decreases bandwidth



Answer : Reduces distortion

29. Spectral density expresses:

(1) Average voltage
(2) Average current
(3) Average power in a waveform as a function of frequency
(4) None of these



Answer : Average power in a waveform as a function of frequency



30. Which of the following is used as a data selector?

(1) Encoder

(2) Decoder

(3) Multiplexer

(4) De-multiplexer



Answer : Multiplexer

31. If a signal x(n)=x(n), then it is called ____ signal:

(1) Odd

(2) Energy

(3) Power

(4) Even



Answer : Even

32. The response of an LTI/LSI system is given by the _______ of input and impulse response:

(1) Convolution

(2) Correlation

(3) Superposition

(4) None


Answer : Convolution


33. Companders are used in communication systems to:

(1) Compress bandwidth
(2) To improve frequency response
(3) To improve signal to noise ratio
(4) None of these



Answer : To improve signal to noise ratio

34. ICB0 in a transistor can be reduced by reducing:

(1) IB

(2) VCC

(3) IE

(4) Temperature



Answer : Temperature


34. Light is confined within the core of a simple optical fiber by:

(1) Refraction.
(2) Total internal reflection at the outer edge of the cladding.
(3) Total internal reflection at the core cladding boundary.
(4) Reflection from the fibers plastic coating.



Answer : Total internal reflection at the outer edge of the cladding.


36. The complement of AB+BC+CD is:

(1) ACD+BC+BD

(2) AC+BC+ABD

(3) AC+BC+ABD

(4) AC+BC+ABD



Answer : ACD+BC+BD

37. The following expression when simplified will become XY(XYZ +XYZ+XYZ)

(1) 0

(2) 1

(3) 1

(4) X



Answer : 0

38. In a PCM system of telemetry, the quantization noise depends on:

(1) The sampling rate and quantization level
(2) The sampling rate only
(3) The number of quantization level
(4) Information provided is not sufficient



Answer : The number of quantization level


39. In PCM system, if we increase the quantization levels from 2 to 8, the relative bandwidth requirements will:

(1) Be doubled

(2) Remain same

(3) Be tripled

(4) Becomes eight times

Answer : Be tripled

40. The modulation system inherently most noise resistant is:

(1) Frequency modulation
(2) Pulse width modulation
(3) Pulse code modulation
(4) Phase modulation

Answer : Pulse code modulation