Electrical Engineering — Fundamentals

Las preguntas del cuestionario

1. 1. The Barkhausen criterion for an oscillator
   1. Loop gain should be unity
   2. Loop gain should be less than unity
   3. The phase of a feedback signal with respect to input should be 0° or 360°
   4. Both A and C
2. 2. Potentiometer method of DC voltage measurement is more accurate than direct measurement using a voltmeter because
   1. It loads the circuit moderately.
   2. It loads the circuit to maximum extent.
   3. It uses centre zero galvanometer instead of voltmeter.
   4. It does not load the circuit at all.
3. 3. Which of these sets of logic gates are designated as universal gates?
   1. NOR, NAND.
   2. XOR, NOR, NAND.
   3. OR, NOT, AND.
   4. NOR, NAND, XNOR.
4. 4. A single phase one pulse controlled circuit has a resistance R and counter emf E load 400 sin(314 t) as the source voltage. For a load counter emf of 200 V, the range of firing angle control is
   1. 30° to 150°.
   2. 30° to 180°.
   3. 60° to 120°.
   4. 60° to 180°.
5. 5. A box which tells the effect of inputs on control sub system is known as
   1. Data Box.
   2. Logical box.
   3. Decision box.
   4. State box.
6. 6. Two infinite parallel metal plates are charged with equal surface charge density of the same polarity. The electric field in the gap between the plates is
   1. same as that produced by one plate.
   2. double the field produced by one plate.
   3. dependent on coordinates of field points.
   4. zero.
7. 7. The resistance in the circuit of the moving coil of a dynamometer wattmeter should be
   1. Low.
   2. Very low.
   3. High.
   4. Almost zero.
8. 8. The following are the necessary requirements of an oscillator
   1. Amplitude stability
   2. Frequency stability
   3. Power stability
   4. Both A and B
9. 9. The normal voltage used in directional heating is
   1. 1.5 KV.
   2. 15 KV.
   3. 33 KV.
   4. 66 KV.
10. 10. LC oscillators are used for produce a waveform with frequency ranging from
    1. 1MHz to 500 MHz
    2. 100 KHz to 500 MHz
    3. 1 KHz to 1 MHz
    4. 1MHz to 100 GHz
11. 11. A working diode must have
    1. High resistance when forward or reverse biased
    2. Low resistance when forward biased, while high resistance when reverse bias
    3. High resistance when forward biased, while low resistance when reverse bias
    4. Low resistance when forward or reverse biased
12. 12. What is the name of the fluorescent material that gives red colour fluorescence?
    1. Zinc silicate.
    2. Calcium silicate.
    3. Zinc sulphide.
    4. Magnesium silicate.
13. 13. How many bits are required to store one BCD digit ?
    1. 1
    2. 2
    3. 3
    4. 4
14. 14. Commutator in DC generator is used for
    1. collecting of current
    2. reduce losses
    3. increase efficiency
    4. convert AC armature current in to DC
15. 15. 1 F is theoretically equal to
    1. 1 ohm of resistance
    2. ratio of 1 V to 1 C
    3. ratio of 1 C to 1 V
    4. none of these
16. 16. How many entries will be in the truth table of a 3 input NAND gate ?
    1. 3
    2. 6
    3. 8
    4. 9
17. 17. In decimal number system what is MSD
    1. First digit from left to right
    2. First digit from right to left
    3. Middle digit
    4. Mean of all digits
18. 18. In Digital Logic Designs, GAL is abbreviated as
    1. General Advance Logic
    2. General Array Logic
    3. Generic Advance Logic
    4. Generic Array Logic
19. 19. Inintel 8085A microprocessor ALE signal is made high to
    1. Enable the data bus to be used as low order address bus
    2. To latch data D0-D7 from data bus
    3. To disable data bus
    4. To achieve all the functions listed above
20. 20. For an SCR gate cathode characteristic is a straight line of 130. For triggered source volume of 15 V and allowable gate power dissipation of 0.5 W compute the gate source resistance?
    1. 111.9 ohm
    2. 11.19 ohm
    3. 108 ohm
    4. 115 ohm
21. 21. The concept of V/f control of inverters driving induction motors resuls in
    1. constant torque operation
    2. speed reversal
    3. reduced magnetic loss
    4. hormonic elimination
22. 22. The energy stored in the magnetic field in a solenoid 30 cm long and 3 cm diameter wound with 1000 turns of wire carrying a current at 10 amp, is
    1. 0.015 joule.
    2. 0.15 joule.
    3. 0.015 joule.
    4. 1.15 joule.
23. 23. While operating on variable frequency supplies, the AC motor requires variable voltage in order to
    1. protect the insulation.
    2. avoid effect of saturation.
    3. improve the capabilities of the inverter.
    4. protect thyristor from dV / dt.
24. 24. Which of the following windings are necessary in case of all dc machines?
    1. closed winding
    2. lap winding
    3. wave winding
    4. open type winding
25. 25. Relaxation Voltage controlled oscillators are used to generate
    1. Sinusoidal wave
    2. Triangular wave
    3. Sawtooth wave
    4. Both B and C