# Typical Questions on Diploma Electrical Engineering

1. A transmission line of 50 W characteristic impedance is terminated with a 100 W resistance. The minimum impedance measured on the line is equal to

(a) 0

(b) 25 W

(c) 50 W

(d) 100 W

2. A cavity resonator can be represented by

(a) An LC circuit

(b) An LCR circuit

(c) A lossy inductor

(d) A lossy capacitor

3. Which one of the following sets of equations is independent in Maxwell’s equations?

(a) The two curl equation

(b) The two divergence equations

(c) Both the curl and divergence equations

(d) The two curl equations combined with the continuity equation

4. A rectangular air filled waveguide has cross section of 4 cm x 10 cm. The minimum frequency which can propagate in the waveguide is

(a) 1.5 GHz

(b) 2.0 GHz

(c) 2.5 GHz

(d) 3.0 GHz

5. Which one of the following materials is a ceramic materials?

(a) Mica

(b) Zinc sulphide

(c) Antimony

(d) Copper

6. Ferrites have

(a) Low copper loss

(b) Low eddy current loss

(c) Low resistivity

(d) High specific gravity compared to iron

7. Dielectric materials are used primarily for

(a) Insulation

(b) Charge storage

(c) Reducing dielectric loss

(d) None of these

8. N-type germanium is obtained on doping intrinsic germanium by

(a) Phosphorous

(b) Aluminium

(c) Boron

(d) Gold

9. Bakelite is

(a) A semiconductor

(b) Incombustible

(c) Low resistance conductor

(d) Highly inflammable

10. Which one of the following is an essential component of electromechanical relays?

(a) Graphite rod

(b) LED

(c) An electromagnet

(d) MOSFET

11. The magnetic permeability is maximum for

(a) Paramagnetic materials

(b) Ferromagnetic materials

(c) Diamagnetic materials

(d) None of these

12. For which one of the following materials is the Hall coefficients zero?

(a) Metals

(b) Insulators

(c) Intrinsic semiconductor

(d) Alloy

13. Which one of the following materials has the highest dielectric strength?

(a) Polystyrene

(b) Marble

(c) Cotton

(d) Transformer oil

14. Metallic copper is a

(a) Paramagnetic substance

(b) Diamagnetic substance

(c) Ferromagnetic substance

(d) Ferrrimagnetic substance

15. Magnetic recording tape is most commonly made from

(a) Small particles of iron

(b) Silicon iron

(c) Ferric-oxide

(d) Silver nitrate

16. Magnetostriction is a phenomenon of

(a) Generation of electricity in ferromagnetic materials

(b) Generation of magnetism in conductors

(c) Change in permeability of ferromagnetic materials during magnetization

(d) Change in physical dimensions of ferromagnetic materials during magnetisation

17. Assuming the Fermi level EF to be independent of temperature, EF may be defined as the level with an occupancy probability of

(a) 0%

(b) 50%

(c) 75%

(d) 100%

18. A 3 H inductor has 2000 turns. How many turns must be added to increase the inductance to 5 H?

(a) 1000 turns

(b) 2500 turns

(c) 2582 turns

(d) 582 turns

19. Superposition theorem is not applicable for

(a) Voltage calculation

(b) Bilateral elements

(c) Power calculations

(d) Passive elements

20. A particular current is made up of two components a 10 A dc and a sinusoidal current of peak value of 14.14 A. The average value of resultant current is

(a) Zero

(b) 10 A

(c) 14.14 A

(d) 24.14 A

21. Two, two-port network are connected in cascade. The combination is to be represented as a single two port network. The parameters of the network are obtained by the multiplying the individuals

(a) Z -parameter matrix

(b) h-parameter matrix

(c) Y-parameter matrix

(d) ABCD parameter matrix

22. A Hurwitz polynomial has

(a) Zeros only in the left half of the s-plane

(b) Poles only in the left half of the s-plane

(c) Zeros anywhere in the s-plane

(d) Poles on the jw axix only

23. If a unit step current is passed through a capacitor, what will be the voltage across the capacitor?

(a) Zero

(b) A step function

(c) A ramp function

(d) An impulse function

24. Voltage transfer function of a simple RC integrator has

(a) A finite zero and a pole at infinity

(b) A finite zero and a pole at the origin

(c) A zero at the origin and a finite pole

(d) A zero at infinity and a finite pole

25. A parallel R-L-C circuit resonates at 100 kHz. At frequency 110 kHz, the circuit impedance will be

(a) Resistive

(b) Capacitive

(c) Inductive

(d) None of the above

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26. Which one of the following has the highest accuracy?

(a) Standard resistance

(b) Standard inductance

(c) Standard capacitance

(d) Standard mutual inductance

27. In a two-wattmeter method of measuring power one of the wattmeter is reading zero watts. The power factor of the circuit is

(a) Zero

(b) 1

(c) 0.5

(d) 0.8

28. No eddy current and hysteresis losses occur in

(a) Electrostatic instruments

(b) PMMC type instruments

(c) Moving iron instruments

(d) Electrodynamometer instruments

29. The phenomena of ‘creeping’ occurs in

(a) Ammeters

(b) Voltmeters.

(c) Watt meters

(d) Watt-hour meters

30. In a single phase power factor meter, the controlling torque is

(a) Provided by spring control

(b) Provided by gravity control

(c) Provided by stiffness of suspension

(d) Not required

31. Torque/weight ratio of an instrument indicates

(a) Selectivity

(b) Sensitivity

(c) Accuracy

(d) Fidelity

32. The pressure coil of a single phase house service energy meter is

(a) Highly resistive

(b) Highly inductive

(c) Purely resistive

(d) Purely inductive

33. The meter constant a single phase 240 V induction wattmeter is 400 revolutions per kWh. The speed of the meter disc for a current of 10 Amps of 0.8 p.f. lagging will be

(a) 12.8 rpm

(b) 16.02 rpm

(c) 18.2 rpm

(d) 21.1 rpm

34. A 10 bit A/D converter is used to digitise an analog signal in the 0 to 5 range. The maximum peak to peak ripple voltage that can be allowed in the D.C. voltage is

(a) Nearly 100 mV

(b) Nearly 50 mV

(c) Nearly 25 mV

(d) Nearly 5.0 mV

35. A 12 bit A/D converter has a range 0-10 V. What is the approximate resolution of the converter?

(a) 1 mV

(b) 2.5 mV

(c) 2.5 μV

(d) 12 mV

36. Schering bridge can be used to measure

(a) Capacitance and its power factor

(b) ‘Q’ of a coil

(c) Inductance and ‘Q’ value

(d) Very small resistance

37. The steady state error due to a ramp input for a type two system is equal to

(a) Zero

(b) Infinite

(c) Constant

(d) Data is insufficient

38. The effect of adding poles and zeros can be determined quickly by

(a) Nichol’s chart

(b) Requisite plot

(c) Bode plot

(d) Root-locus

39. Nichol’s chart is useful for detailed study and analysis of

(a) Close loop frequency response

(b) Open loop frequency response

(c) Close loop and open loop frequency response

(d) None of these

40. Signal flow graph is used to find

(a) Stability of the system

(b) Controllability of the system

(c) Poles of the system

(d) Transfer function of the system

41. Derivate feedback control

(a) Increase feedback time

(b) Increase overshoot

(c) Decrease steady state error

(d) Does not affect the steady state error

42. With negative feedback in a closed loop control system, the system sensitivity to parameter variations

(a) Increases

(b) Decreases

(c) Becomes zero

(d) Becomes finite

43. If the magnitude of the polar plot at phase crossover is ‘a’, the gain margin is

(a) –a

(b) 0

(c) a

(d) 1/a

44. The initial slope of the bode-plot gives an indication of

(a) Type of the system

(b) Nature of the system time response

(c) System stability

(d) Gain margin

45. The induced e.m.f. in the armature conductors of a d.c. motor is

(a) Sinusoidal

(b) Trapezoidal

(c) Rectangular

(d) Alternating

46. Which of the following d.c. motor would be suitable for drives requiring high starting torque but only fairly constant speed such as crushers?

(a) Shunt motor

(b) Series motor

(c) Compound motor

(d) Permanent magnet motor

47. Cogging of induction motor occurs due to

(a) Harmonic synchronous torque only

(b) Vibration torque

(c) Harmonic induction torque only

(d) Both synchronous and induction torque

48. At a slip of 4% the maximum possible speed of three phase squirrel cage induction motor is

(a) 1440 rpm

(b) 1500 rpm

(c) 2880 rpm

(d) 3000 rpm

49. Slip ring are made of

(a) Steel

(b) Copper

(c) Bakelite

(d) Mica

50. The efficiency of a 3 phase induction motor is approximately proportional to

(a) (1-S)

(b) S

(c) N

(d) Ns