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24th July 2014, 01:28 PM
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Join Date: Apr 2013
Re: Rubber board Junior Assistant written test model paper

Here is the Rubber board Junior Assistant written test model paper:

1. The lowest temperature coefficient metal is
(A) Molybdenum. (B) Kantal. (C) Mangenin. (D) Nicrome
2. Density of gold is approximately equal to the density of
(A) Platinum (B) Tungstun (C) Nicrome (D) Kantal
3. For long- distance transmission lines which of the following is preferred
(A) Aluminium (B) Kantal (C) Copper (D) A mixture of Copper and Aluminium.
4. Resistivity range of semiconductors lies between the range of
(A) 10-3 to 103 ohm-m (B) 10-5 to 105 ohm-m (C) 10-3 to 105 ohm-m (D) 10-5 to 103 ohm-m
5. Which out of the following is a poorest insulator ?
(A) Bakelite (B) Lucite (C) Rubber (D) Polyethylene
6. Due to the free electrons moving in the metals the potential energy of the free electrons is
(A) Very high (B) Positive (C) Zero (D) Negative
7. Quantum states with the same energies are said to be
(A) Complementary states (B) degenerate states (C) equal energy states (D) None of these.
8. The probability of occupation P (E) of an energy level E by an electron is given by
(A) P (E) = 1/1+e(EF - E) / KT (B) P (E) = [1+e(E - EF)] / KT (C) (P (E) = 1/1+e(E - EF) / KT D) None of these
9. The wave number can take
(A) only negative values. (B) only positive values (C) both Positive or negative values. (D) all real values possible
10. 7.18o K is the critical temperature of
(A) V (B) Ta (C) Po (D) V3Si.
11. At critical temperature T c the value of the critical magnetic field He is
(A) zero (B) some finite value, which depends upon the structure of the material. (C) infinity (D) None of these
12. Which of the following properties of the superconductor is a structure sensitive property ?
(A) Critical magnetic field strength H c (B) Critical temperature T c (C) Critical current density J c (D) None of these.
13. A quantum state has 19 for the sum of the squares of the quantum numbers n x, n y, n z. What is the degeneracy of state ?
(A) 22 (B)19 (C) 20 (D) 24
14. The order of energy gaps between the valance band and the conduction band in insulators and semi- conductors is
A) 10eV, 4eV (B) 6eV, 4eV (C) 6eV, 1eV (D) 1eV, 3eV
15. Mark the true statement.
A) Iron is greatly used for making permanent magnets. (B) Paper can’t affect magnetic lines of force or magnetic flux
(C) ALNICO is commonly used for making electromagnets (D) Ferrites has lower permeability than air or vacuum.
16. A closed switch has ideally a resistance of
(A) zero ohm (B) infinite ohm (C) at least 100 ohm at any temperature (D) about 100 ohm at room temperature
17. If an electric flux density Do passes across a negatively charged surface the density of the flux
(A) remains same (B) decreases (C) increases (D) may increase or decrease
18.Which of the following is not an elemental semiconductor
(A) Te (B) C (C) B (D) Br
19. The potential energy of an electron is
(A) constant and does not vary with the distance of electron from the atom (B) more when it is close to the positive ion
(C) less it is close to the positive ion. (D) less when it is far from the positive ion
20. If the amplitude of the standing wave at a point is A, then the probability of finding an electron at that point is proportional to
(A) A3 (B) A2 (C) A (D) A1.732
21. In monovalent metals the outer most energy band is
(A) empty (B) full (C) half- filled (D) any of (A) or (B)
22.The Probability P (E) of an electron occupying energy level E becomes
(A) P (E) = 1/1-exp[(E-EG) /kT] (B) P (E) = exp(-2 Eg/kT) (C) P (E) = exp (-2 EgkT) (D) None of these
23. A n-type semiconductor has excess of free electrons and a p-type semiconductor has deficiency of free electron.
The semi- conductors are electrically
(A) positively charged and negatively charged respectively (B) negatively charged and positively charged respectively
(C) both are electrically neutral (D) None of these
24.In zone refining section the purity achieved is better than
(A) 99.9% (B) 99.99% (C) 99.999% (D) 99.9999%
25.If the acceptor level is 0.16eV above the top of the valence band, the fractions of hole present at 300 K is
(A) 6.10 * 10-4 (B) 2.05 * 10-3 (C) 5.01 * 10-3 (D) 9.23 * 10-4
26.Make the false statement out of the following
(A) Phosphorous has 5 valence electron
(B) Hole current is the movement of positive charges in the opposite direction from electron flow
(C) The internal barrier potential at PN junctions for silicon is approximately 1.1 eV
(D) None of these.
27. All the materials with a basic unit, which has a center of symmetry i.e. starting from the center and drawing a vector to one of the
surrounding ions, one finds a similar ion at a position. Corresponding to a vector of equal length drawn in the opposite direction, are
known as
(A) Magneto striction (B) Piezoelectric (C) Electrostriction (D) None of these
28. The relative permeability of diamagnetic material is of the order of
(A) 1+ 10-5 (B) 10-5 (C) 1-10-5 (D) 105
29.The ferromagnetic curies temperature in degrees absolute for iron is
(A) 990 (B) 1428 (C) 631 (D)1043
30.Which of the following material is used for making permanent magnets
(A) Alnico V (B) Carbon Steel (C) Plantinum cobalt (D) All of these
31.If a number of domains are arranged such that no poles exists at the surface and no lines of force go out of the material the
magnetostatic energy of a ferromagnetic material
(A) reduces (B) remains the same (C) increases (D) it may increase or decrease
32.On the application of an electric field, a polarisation process occurs as a function of time. the polarisation p (t) as a function
of time t is given by
(A) P (t) = P
/[exp(-t/tr) + 1] (B) P (t) = P/[1-exp(-t/tr)] (C) P (t) = P[1-exp(-t/tr)] (D) None of these
33. A constant voltage generator has
(A) low internal resistance (B) minimum efficiency (C) high internal resistance (D) minimum current capacity
34. which of the following is a low pass filter ?
(A) L type with series C and shunt L (B) T type with series L and shunt C
(C) T type with series C and shunt L (D) L type with series L and shunt C
35.With an indirectly heated cathode the heater voltage
(A) must be a steady d.c. voltage (B) is separate from the cathode circuit
(C) is applied to the cathode (D) is equal to the c-bias voltage
36.Which is single 8-input NAND gate ?
(A) SN 7430 (B) SN 7432 (C) SN 7440 (D) SN 7410
37. EZ-80 in radio is a
(A) full wave rectifier (B) audio amplifier (C) line output pentode (D) None of these
38.In LED, light is emitted because
(A) We make the light fall on LED (B) recombination of charges takes place (C) diode emits light when heated (D) None of these
39.which of the following has the highest voltage gain ?
(A) CB (B) CE (C) CC (D) None of these
40.(i)Transistors on a monolithic linear IC unit are generally PNP on a silicon substrate
(ii) typical values of L integrated on a chip are 10 to 100 mH.
Indicate correct combination
(A) F, F (B) T, F (C) F, T (D) T, T
41. Bridge rectifiers are preferred because
(A) less peak inverse voltage (B) they require small transformer (C) Both (A) & (B) (D) None of these
42.Triac is a
(A) 2 terminal unilateral switch. (B) 3 terminal bidirectional switch (C) 2 terminal bidirectional switch (D) 3 terminal unilateral switch
43. SCS is a device which is
(A) physically smaller than SCR and operates at lower current and voltage (B) physically larger
(C) physically smaller but operates at high current and voltage as compared to SCR.
(D) physically larger and operate at high voltage and current
44.Thyristor can be turned off
(A) by reversing the anode voltage (B) by reducing the anode current below holding current value
(C) Both (A) & (B) (D) None of these
45.SN 7410 IC is a
(A) triple 3 input Nand gate (B) triple 3 input Nand with open collector (C) 2- input Nand gate (D) None of these
46. h22 hybrid parameter is
(A) out put conductance with input open circuited (B) input resistance with output open circuited
(C) output resistance with input open circuited (D) input conductance with output open circuited.
47.Cascade configuration is
(A) CE- CC (B) CE- CE (C) CE-CB (D) CE- CE
48.Class B and Class C operations are used in (respectively)
(A) tunned amblifiers (B) untunned and tunned amblifiers (C) tunned and untunned amblifiers (D) untunned amblifiers
49. In Voltage series negative feedback Ri and Rof
(A) increases, decreases as compared to previous value (B) increases, increases (C) decreases, increases (D) decreases, decreases
50.Pushpull amplifier result in
(A) less distortion and more output power (B) less distortion, less output power
(C) more distortion , more output power (D) more distortion , less output power
51.Class B push pull amblifier suffers from
(A) cross over distortion (B) inter modulation distortion (C) excessive harmonic distortion (D) None of these
52. In trans- resistance amplifiers
(A) O/P current depends on input voltage. (B) O/P voltage depends on input current
(C) O/P voltage depends on input voltage. (D) O/P current depends on input current.
53. With negative feed back, the Rof (output) and Rif (input) impedance in case of voltage series feedback amblifier, respectively
(A) increases, increases (B) decreases, decreases (C) increases, decreases (D) decreases, increases
54. Emitter follower is characterised by
(A) low output impedance and little distortion (B) low output impedance and more distortion
(C) more output impedance and more distortion (D) None of these
55.The effect of bypass capacitor in amplifier design is adversely seen on
(A) low frequency response (B) medium frequency response (C) high frequency response (D) None of these
56. if the input resistance is reduced in tube amplifier then the power gain of the driving amplifier for moderate feedback, and the
voltage gain respectively
(A) increases, decreases (B) both increases (C) both decreases (D) remain same
57.Conversion efficiency for class A and B respectively are
(A) 25, 50% (B) 50, 50% (C) 50, 25% (D) 50, 78.4%
58. cascade amplifiers are used in
(A) tunned amplifier design (B) video amplifier (C) voltage amblifier (D) power amplifier
59. The high frequency response of an amplifier can be determined from
(A) hybrid – T- model (B) h-parameter model of the amplifier (C) hybrid pie -model (D) None of these
60.The dynamic impedance of a Zemer diode
(A) decreases with increase in current passing through it (B) increase with increase in current passing through it
(C) is independent of current passing through it (D) None of these
61. Ripple factor (r) of an inductance can be calculated from the formula
(A) r = 2410/LRL (B) r = RL/1600L (C) r = 1600L/RL (D) None of these
62.The purpose of an amplifier is
(A) to increase voltage and current of an input signal (B) to introduce distortion in the signal fed to it
(C) to attenuate the single fed to its point (D) to increase voltage current or power of an input signal.
63.The standard aircraft frequency is
(A) 60 Hz (B) 50 Hz (C) 400 Hz (D) None of these
64. Conversion efficiency for the amplifier is signal power delivered
(A) n = to load / d.c power supplied to output circuit *100 (B) n = output power/input power *100
(C) n = output circuit / signal power delivered to load *100 (D) None of these
18th August 2014, 03:54 PM
Re: Rubber board Junior Assistant written test model paper

where can i get the answers pls ?
23rd August 2014, 08:50 AM
Re: Rubber board Junior Assistant written test model paper

can you please provide me answer key for these questions?
email- jyothibasur5@gmail.com

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