Question Bank on Diploma Electronics Engineering

1. The temperature co-efficient of resistance of a semiconductor is
(a) +ve
(b) –ve
(c) Zero
(d) very high

2. In an unbiased P-N junction, thickness of depletion layer is of the order of
(a) 0.005μm
(b) 0.5 μm
(c) 5 μm
(d) 1nm

3. JFET can operate in
(a) depletion mode and enhancement mode
(b) depletion mode only
(c) enhancement mode only
(d) neither enhancement nor depletion mode

4. FETs have similar properties to
(a) PNP transistors
(b) NPN transistors
(c) thermionic valve
(d) UJTs

5. Which statement about MOSFET is false? MOSFETs can operate in
(a) depletion mode
(b) enhancement mode
(c) both depletion & enhancement mode
(d) depletion only mode

6. In a JFET, point of reference is
(a) Drain
(b) Source
(c) Gate
(d) none of these

7. Input gate current of a FET is
(a) a few microampere
(b) negligibly small
(c) a few milliamperes
(d) a few amperes

8. For enhancement only mode N-channel MOSFET polarity of Vgs is
(a) –ve
(b) +ve
(c) Zero
(d) variable

9. In a JFET operating above pinch-off voltage, the
(a) drain current increases steeply
(b) drain current remains constant
(c) drain current starts decreasing
(d) depletion region become smaller

10. The best electronic device for fast switching is
(a) BJT
(b) Triac
(c) JFET

11. Which semiconductor device acts like a diode and two resistors?
(a) SCR
(b) Triac
(c) Diac
(d) UJT

12. Which semiconductor device behaves like two SCRs?
(a) UJT
(b) Triac
(c) JFET

13. After firing an SCR, the gating pulse is removed. Then the current in the SCR will
(a) remain same
(b) fall to zero
(c) rise up
(d) rise a little then fall to zero

14. The oscillator circuit that uses a tapped coil in the tuned circuit is
(a) Multivibrator
(b) Hartley
(c) Colpits
(d) Armstrong

15. An oscillator produces oscillations due to which type of feedback?
(a) +ve feedback
(b) –ve feedback
(c) Both +ve & –ve
(d) neither +ve nor –ve

16. Frequency stability in an oscillator can be achieved by
(a) adjusting the phase shift
(b) controlling its gain
(c) incorporating a tuned circuit
(d) employing automatic biasing

17. An oscillator that consists of two interdependent circuits such that output of each controls the input of the other is called a
(a) sine wave oscillator
(b) feedback oscillator
(c) relaxation oscillator
(d) –ve resistance oscillator

18. The Wien bridge oscillator is
(a) a free running oscillator
(b) a square wave generator
(c) a stable sine wave generator
(d) also called cosine oscillator

19. If the frequency of incoming rectangular wave in a staircase generator is 100Hz, the number of steps in the output staircase pattern is
(a) 100
(b) 200
(c) 300
(d) 500

20. Resistance of an accurate ammeter is
(a) High
(b) Low
(c) very low
(d) very high

21. The duty cycle of a pulse of width 2 microsecond and repetition frequency 4kHz is
(a) 0.5
(b) 0.06
(c) 0.008
(d) 0.8

22. Deflection sensitivity of a CRO is
(a) directly proportional to
(b) inversely proportional to
(c) does not depend on distance between the deflecting plate and screen
(d) none of these

23. Noise figure of a two stage amplifier depends on the gain of
(a) first stage
(b) second stage
(c) both the stages
(d) none of the stages

24. Wien bridge is usually used for measuring
(a) Resistance
(b) Capacitance
(c) frequency
(d) current

25. The Kelvin double bridge is used for measuring accurately
(a) low value resistors
(b) high value resistors
(c) any resistors
(d) inductors

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26. Under identical values of cold and hot junction temperatures, which thermocouple gives the highest output?
(a) iron constantan
(b) nickel iron
(c) chromal constantan
(d) platinum rhodium

27. A delay line is used in high speed CRO to introduce time delay in
(a) vertical channel
(b) horizontal channel
(c) z axis of the CRT
(d) all of the above

28. For dc voltage an inductor behaves like a
(a) short circuit
(b) open circuit
(c) depends on polarity
(d) depends on voltage

29. A connected planar network has 4 nodes and 5 elements. The number of meshes in its dual network is
(a) 4
(b) 3
(c) 2
(d) 1

30. If there are b branches and n nodes in a network, then the number of independent KVL equations will be
(a) b
(b) b–n
(c) n–1
(d) b–n+1

31. In a linear network containing only independent current sources and resistors, if the values of all the current sources are doubled then the values of node voltages will be
(a) Doubled
(b) Halved
(c) same
(d) none of these

32. Which of the following theorem is a manifestation of the law of conservation of energy?
(a) Thevenin’s theorem
(b) Telegan’s theorem
(c) Reciprocity theorem
(d) compensation theorem

33. When a source is delivering maximum power to a load, the efficiency of the circuit
(a) is always 50%
(b) is always 75%
(c) depends on the
(d) none of these parameters

34. Twelve 1Ω resistances are used as edges to form a cube. The resistance between two diagonally opposite corners of the cube is
(a) 6/5Ω
(b) 1Ω
(c) 5/6Ω
(d) 6Ω

35. The ratio of active power to apparent power is known as
(a) power factor
(b) load factor
(c) form factor
(d) demand factor

36. The transient current in an RLC circuit is oscillating when
(a) R = 2√(L/C)
(b) R>2√(L/C)
(c) R< 2√(L/C)
(d) R = 0

37. A coil with a certain number of turns has a specified time constant. If the no. of turns is doubled, the time constant will be
(a) Halved
(b) Doubled
(c) become four fold
(d) unaffected

38. An R-L-C series circuit has R=1Ω, L=1H, and C=1F. Damping ratio of the circuit will be
(a) >1
(b) Unity
(c) 0.5
(d) zero

39. A series R-L circuit with R=100Ω, L=50H is connected to a dc source of 100V. The time taken for the current to rise to 70% of its steady value is
(a) 0.2s
(b) 0.6s
(c) 2.4s
(d) none of these

40. The steady state current in the R-C series circuit on the application of a step voltage of magnitude E will be
(a) Zero
(b) E/R
(c) (E/R) ℮ -t/RC
(d) (E/RC) ℮ -t

41. When an unit impulse voltage is applied to an inductor of 1H, the energy supplied by the source is
(a) ∞
(b) 1 Joule
(c) 0.5 Joule
(d) zero

42. An initially relaxed R-C series network with R=2MΩ and C=1μF is switched on to a 10V step input. The voltage across the capacitor after 2sec will be
(a) Zero
(b) 3.68V
(c) 6.32V
(d) 10V

43. A network has seven nodes and five independent loops. The number of branches in the network is
(a) 5
(b) 7
(c) 11
(d) 13

44. If all the elements in a particular network are linear then the superposition theorem holds, when the excitation is
(a) dc
(b) ac
(c) dc or ac
(d) impulse

45. Two coils having equal resistances but different inductances are connected in series. The time constant of the series combination is the
(a) sum of the time constants of the individual coils
(b) average of the time constants of the individual coils
(c) geometric mean of the time constants of the individual coils.
(d) Product of the time constants of the individual coils.

46. Which of the following pair is correctly matched?
(a) symmetrical two port network : AD – BC = 1
(b) reciprocal two port network : Z11 = Z22
(c) inverse hybrid parameters : A, B, C, D
(d) hybrid parameters : (V1 , I 2) = f(I 1, V2)

47. For a two port network to be reciprocal, it is necessary that
(a) Z11 = Z22 and Y12 = Y21
(b) Z11 = Z22 and AD – BC = 0
(c) h21 = – h12 and AD – BC = 0
(d) Y12 = Y21 and h21 = – h12

48. With usual notation a two port resistive network satisfied the condition A = D = (3/2)B = (4/3)C The Z11 of the network is
(a) (5/3)Ω
(b) (4/3)Ω
(c) (2/3)Ω
(d) (1/3)Ω

49. A system has a single pole. The constant multiplier ‘k’ is 1. For the given excitation sin(t), the response is √2 with 45º lagging. The system has a pole and a zero respectively at
(a) zero and 1
(b) ∞ and – 1
(c) – 1 and zero
(d) zero and – 1

50. The frequency at which two asymptotes meets is known as
(a) corner or break frequency
(b) threshold frequency
(c) cut off frequency
(d) critical frequency