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BSNL Placement Paper
1. For a parallel plate capacitor which is being charged out of the following the incorrect statement is
a. Energy stored in the capacitor does not enter it through the connecting wire through the space around the wires and plates of capacitor.
b. Rate at which energy flows into this volume is equal to the integration of the pointing vector over the boundary of the volume between the plates.
c. The pointing vector points everywhere radially outward of the volume between plates.
d. The pointing vector points everywhere radially into the volume between the plates.
2. The presence of alkali oxides in alumino silicate ceramics is likely to result in dielectric breakdown due to
a. Polarization
b. Conductivity
c. Structural homogeneties
d. Ionization
3. Which of the following will serve as a donor impurity in silicon
a. Boron
b. Indium
c. Germanium
d. Antimony
4. Electrical contact materials used in switches, brushes and relays must possess
a. High thermal conductivity and high melting point
b.Low thermal conductivity and low melting point
c. High thermal conductivity and low melting point
d. Low thermal conductivity and high melting point
5. The Maximum spectral response of the germanium and silicon is in the
a. infrared region
b. ultraviolet region
c. visible region
d. x-ray region
6. For an insulating material, dielectric strength and dielectric loss should be respectively
a. high and high
b. low and high
c. high and low
d. low and low
7. In a distortion factor meter, the filter at the front end is used to suppress
a. odd harmonics
b. even harmonics
c. fundamental component
d. dc component
8. The coefficient of coupling between two air core coils depends on
a. mutual inductance between two coils only
b. self inductances of the two coils only
c. mutual inductance and self inductances of the two coils
d. none
9. Modern capacitors which have high capacitance in small size use a dielectric of
a. paper
b. rubber
c. ceramic
d. Mylar
10. In any atom the potential energy of an orbiting electron is
a. always positive
b. always negative
c. sometime positive, sometime negative
d. numerically less than its kinetic energy
11. A DE MOSFET differs from a JFET in the sense that it has no-
a. channel
b. gate
c. P-N junctions
d. substrate
12. The advantage of a semiconductor strain gauge over the normal strain gauge is that
a. it is more sensitive
b. it is more linear
c. it is less temperature dependent
d. it's cost is low
13. Barrier potential in a P-N junction is caused by
a. thermally generated electrons and holes
b. diffusion of majority carriers across the junction
c. migration of minority carriers across the junction
d. flow of drift current
14. When an NPN transistor is properly biased then most of the electrons from the emitter
a. recombine with holes in the base
b. recombine in the emitter itself
c. pass through the base to the collector
d. are stopped by the junction barrier
15. The value of r when a transistor is biased to cut off is-
a. 0.5
b. 0
c. 1.0
d. 0.8
16. A UJT can
a. be triggered by any one of it's three terminals
b. not be triggered
c. be triggered by two of its three terminal only
d. be triggered by all of its terminals only
17. An SCR can only be turned off via it's
a. cathode
b. anode
c. gates
d. none
18. Gold is often diffused into silicon DN junction devices to
a. increase the recombination rate
b. reduce the recombination rate
c. make silicon a direct gap semiconductor
d. make silicon semi-metal
19. With n nodes and b branches a network will have
a. (b + n) links
b. b-n + 1 links
c. b-n-1 links
d. b + n + 1 links
20. When a network has 10 nodes and 17 branches in all then the number of node pair voltages would be
a. 7
b. 9
c. 10
d. 45
21. A two port network having a 6 dB loss will give
a. an output power which is one-quarter of the input power
b. an output power which is one-half of the input power
c. an output voltage which is 0.707 of the input voltage
d. an output power which is 0.707 of the input power
22. While transporting a sensitive galvanometer-
a. the terminals are kept shorted
b. critical damping resistance is connected across the terminals
c. the terminals are kept open circuited
d. it does not matter as to what is connected across the terminals
23. A T type attenuator is designed for an attenuation of 40 dB and terminating resistance of 75 ohms. Which of the following values represent full series and R1 and shunt arm R2?
1. R1 = 147W
2. R1 = 153W
3. R2 = 1.5W
4. R2 = 3750W
a. 1 and 3
b. 1 and 4
c. 2 and 3
d. 2 and 4
24. For a transmission line, the characteristic impedance with inductance 0.294mH/m and capacitance 60pF/m is
a. 49w
b. 60w
c. 70w
d. 140w
25. When the graph of a network has six branches with three tree branches then the minimum number of equations required for the solution of the network is
a. 2
b. 3
c. 4
d. 5
26. Consider the following statement for a 2 -port network
1. Z11 = Z22
2. h12 = h21
3. Y12 =-Y21
4. BC-AD =-1
then the network is reciprocal if and only if
a. 1 and 2 are correct
b. 2 and 3 are correct
c. 3 and 4 are correct
d. 4 alone is correct
27. As a network contains only independent current sources and resistors then if the values of all resistors are doubled then the values of the node voltages are
a. will become half
b. will remain high
c. will become double
d. cannot be determined unless the circuit configuration and the values of the resistors are known
28. The energy of electric field due to a spherical charge distribution of radius r and uniform charge density d in vacuum is-
Ans. 5.4x109xQ2/r where Q=4/3(pie.r3d
29. Maxwell's divergence equation for the magnetic field is given by
Ans. y
30. When a short grounded vertical antenna has a length L which is 0.05 l at frequency f and if it's radiation resistances at f is R Ohms, then it's radiation resistance at a frequency 2f will be
a. R/2 ohms
b. R ohms
c. 2R ohms
d. 4R ohms
