TNEB 2016 Assisant Engineer recruitment ECE questions

Part - 3 (ECE)

1.For a D/A converter, the resolution required is 50mV ad the total maximum input is 10 V.
The number of bits required is

a) 7
b) 8
c) 9
d)200

Ans: Option b)

2. An OPAMP has a slew rate of 100V/msec. For a frequency of 10 MHz, the maximum value of sine wave output voltage will be
a) 100V

b) 50/π V

c) 10 V

d) 5 V

Ans: Option b)

3. The oscillator with the best frequency stability and accuracy is

a) Hartley oscillator

b) Colpitts Oscillator

c) Tickler feedback Oscillator

d) Crystal Controlled Oscillator

Ans: Option d)

4. In Output of a DM speech encoder, the consecutive pulses are of opposite polarity during time interval t1
a) Input to the modulator is essentially constant
b) Modulator is going through slope overload
c) Accumulator is in saturation
d) Speech signal is being sampled at Nyquist rate

Ans: Option a)

5. A silicon diode is operating at 25^oC with a forward bias of 0.6 V and a current of 0.5 A. If the current is held constant at 0.5 A and the temperature of the device is raised to 75^oC, the voltage across the diode is likely to be

a) 0.49 V

b) 0.60 V

c) 0.66 V

d) 0.75 V

Ans: Option a)

6.  One of the following microwave diodes is suitable for very low power oscillator

a) Tunnel

b) Gunn

c) IMPATT

d) LSA

Ans: Option a)

7. Frequency Shift Keying is used mostly in

a) Radio Transmission

b) Telegraphy

c) Telephony

d) Television

Ans: Option c)

8. Fourier  transform of a unit step signal is

a)    πδ(ω)
b)    1/jω
c)    πδ(ω) + 1/jω
d)    πδ(ω) - 1/jω

Ans: Option c)

9. An Amplifier is said to suffer from distortion when its output is
a) Low
b) different from its input
c) noisy
d) larger than its input

Ans: Option b)

10. Backlash in a stable control system can cause 
a) Over damping
b) Low level Oscillations
c) Under damping
d) Poor Stability at reduced values of open loop gain

Ans: Option b)
 
11. The number of multiplications needed to compute a 32 point DFT using radix-2 FFT algorithm is
a) 80
b) 60
c) 40
d) 20

Ans: Option a)

12. The content of a 4-bit register is 1101. The register is shifted 6 times to the right with serial input being 101101. The final content of register will be
a) 1011
b) 0111
c) 0010
d) 1010

Ans: Option a)

13. Fibers have numerical aperture in the region of 0.15 to 0.4. Fibers with higher N.A. values generally exhibit
a) Reduced losses
b) High bandwidth
c) Reduced losses and low bandwidth
d) Greater losses and low bandwidth


Ans: Option d)

14. A D/A converter has 5V full scale output voltage and an accuracy of ± 0.2%. The maximum error for any output voltage will be 

a) 5 mV

b) 10 mV

c) 20 mV

d) 25 mV

Ans: Option b)

15. For a dominant mode, in a rectangular waveguide with breadth 10 cm, the guide wavelength for a signal of 2.5 GHz will be

a) 20cm

b) 18 cm

c) 15 cm

d) 12 cm

Ans: Option c)

16. Radiation from a helical antenna is

a)  Plane polarised 

b) partially plane polarised

c) Circularly Polarised

d) Elliptically Polarised

Ans: Option c)

17. The cavity magnetron uses strapping to
a) ensure bunching
b) prevent cathode back-heating
c) prevent mode skipping
d) improve phase focusing effect

Ans: Option c)

18. Intrinsic impedance of free space

a) 120Ω

b) 100Ω 

c) 277Ω 

d) 377Ω 

Ans: Option d)

Part II - Basic Engineering  and Science

1. Two computers communicating simultaneously comes under the category

a) Serial

b) Full Duplex

c) Half Duplex

d) Simplex

Ans: Option b)

2. The ------------ layer decides the location of synchronization points
a) Network
b) Transport
c) Presentation
d) Session
Ans: Option b)

 

3. Which of the following addressing modes is convenient to handle pointers?
a) Immediate and Direct addressing 
b) Indirect addressing
c) Base addressing
d) Relative addressing


Ans: Option c)

4. Ohm's law is applicable to 
a) Silicon Carbide
b) Zener diode
c) Voltage Regulator tube
d) Copper

Ans: Option d)

5. The material in which spontaneous polarization changes with temperature is known as 
a) Piezoelectric
b) Ferroelectric
c) Pyroelectric
d) Magneto optic
Ans: Option c)

6. A mode of fracture that is caused by extensive plastic deformation is called 
a) Brittle fracture
b) Ductile fracture
c) Plastic fracture
d) Fatigue fracture

Ans: Option d)

7. The dimension of ferromagnetic domains is in the order of 

a) 10⁶ m

b) 10^{-9 m}

c) 10^{-6 m}

d) 10^-3 m

 ^{Ans: Option c)}

8. Which of the following is true? K and σ are thermal and electrical conductivity in a solid, according to Wiedemann-Franz law
a)    KT/ σ = constant
b)    Kσ/T = constant
c)    σ/KT = constant
d)    K/ σT = constant
 
Ans: Option d) 

9. The idea of the quantum nature of light is required to explain 
a) interference of light
b) thermionic emission
c) Radioactivity
d) Black body radiation

Ans: Option d)  

10. The wavelength of emission from He-Ne laser is
a) 10.64 µ m
b) 337.1 nm
c) 694.3 nm
d) 632.8 nm

Ans: Option a) 

11. An optical fibre has a core material of refractive index of 1.55 and cladding material of refractive index of 1.50. The numerical aperture of the fibre is
a) 0.05
b) 0.39
c) 3.05
d) 0.90

Ans: Option b)

12.  The increase in order of carbon content of the different types of coal is given by
a) Peat   <  Sub-bituminous coal  < Bituminous Coal  <  Anthracite
b) Peat   <  Bituminous coal  < Sub -bituminous Coal  <  Anthracite
c) Anthracite   <  Sub-bituminous coal  < Bituminous Coal  <  Peat
d)  Anthracite   <  Bituminous coal  <  Sub-bituminous Coal  <  Peat

Ans: Option a)

13. Ethernet belongs to
a) IEEE 802.2
b) IEEE 802.3
c) IEEE 802.4
d) IEEE 802.5

Ans: Option b)

14.  The purpose of including an external resistance at the time of starting a DC motor is to
a) increase the starting torque
b) increase the armature flux
c) reduce the starting current
d) maintain the constant flux

Ans: Option a)

15. Which of the following can be used to extend the range of an ammeter?
a) A low resistance in series with the ammeter
b) A high resistance in series with the ammeter
c) A low resistance in parallel with the ammeter
d) A high resistance in parallel with the ammeter