Synopsis of Electrical Engineering

1.        When a pumped storage power plant is operated in conjunction with a steam power plant a.        The operating cost of the steam plant becomes optimum b.       Load factor of the steam plant is increased c.        Chances of the tripping of the system decreases because of the use of two heterogeneous types of plants d.       Operation of the storage plant in the pumping mode during the low-load period improves the steam-plant stability 2.        Usage of materials in components of a nuclear reactor:     Graphite is used in moderators;   Boron is used in control rods ;   Sodium is used as a coolant ;  Concrete is used as a shield 3.        A 100km long transmission line is loaded at 110kV. If the loss of line is 15MW and the load is 150MVA, t...

Important Multiple Choice Questions on Electrical Machines 1.        Can a 50Hz transformer be used for a 25Hz if the input voltage is maintained constant at the rated value corresponding to 50Hz? a)       Yes. Since the voltage is constant, current levels will not change. b)       No. Flux will be doubled which will drive the core excessive saturation. c)        No. Owing to decreased reactance of transformer, input current will be doubled at load. d)       Yes. At constant voltage, insulation will not be overstressed. 2.        In a transformer, if the iron losses and copper losses are 40.5 kW and 50 kW respectively, then at what fraction of load will be the efficiency be maximum? a)       0.8 b)       0.57 c)        0.7 d...

Important multiple choice questions on Electrical Machines 1.        To eliminate the single phasing torque in an ac servomotor, the rotor must have a)       Both high resistance and reactance. b)        High resistance. c)        High reactance. d)       Large air-gap 2.        If a single-winding single-phase motor is running in a particular direction a)       Both the rotating fields (rotating in opposite directions) have the same strength. b)       Forward rotating field is slightly stronger than the backward field. c)        Forward rotating field is much stronger than the backward field. d)       Backward field is stronger than the forward field. 3.        A...

Important Multiple Choice questions on Power Systems 1.        For transmission line which one of the following relations is true? A)      AD-BC=1 B)       –AD-BC=1 C)       AD-BC=-1 D)      AD-BC=0 2.        For a given base voltage and base volt-amp, the per unit impedance value of an element is X. what will be the per-unit impedance value of this element when the voltage and volt-amp bases are both doubled? A)      4X B)       2X C)       X D)      0.5X 3.        A 3-phase transmission line has its conductors at the corners of an equilateral triangle with side 3m. the diameter of each conductor is 1.63 cm. the inductance of the line per phase per km is A)      1.232 mH B)...

Important Multiple Choice Questions in Electrical Circuits 1.        When a number of 2 port networks are connected in cascade, then equivalent can be obtained by A)      Adding individual Z matrices B)       Adding individual Y matrices C)       Multiplying  individual Chain matrices D)      Multiplying  individual h matrices 2.        A periodic function is said to have a quarter wave symmetry, if it possesses A)      Even symmetry at an interval of quarter of a wave B)       Even symmetry and half-wave symmetry only C)       Even or odd symmetry without the half wave symmetry D)      Even or odd symmetry with the half wave symmetry 3.        A ramp voltage v(t)=100 V, is applied to a...

Important Multiple Choice Questions in Electrical Circuits 1.        The energy stored in the magnetic field at a solenoid 30 cm long and 3 cm diameter wound with 1000 turns of wire carrying a current at 10A, is A)      0.015 Joule B)       0.15 Joule C)       0.5 Joule D)      1.15 Joule 2.        For a transfer function H(s)= P(s)/Q(s), where P(s) and Q(s) are polynomials in s. Then A)      The degree of P(s) is always greater than the degree of Q(s) B)       The degree of P(s) and  Q(s) are same C)       The degree of P(s) is independent of the  degree of Q(s) D)      The maximum degree of P(s) and  Q(s) differ at most by one 3.        The resistance of a strip of copper of re...