Synopsis of Electrical Engineering

Important Multiple Choice Questions on Electrical Machines 1.        Transformer excited from a sinusoidal voltage source will draw a no-load current which A)      Is sinusoidal and of the same frequency as the voltage source B)       Comprises the fundamental frequency (same as that of the voltage source) and the peaking third harmonic C)       Comprises the fundamental frequency and the depressing third harmonic D)      Is sinusoidal of frequency three times that of the voltage source 2.        A transformer on no-load is switched on to a source of voltage. It will draw a current which A)      The same as the steady-state magnetizing current B)       Several times the steady-state magnetizing current depending upon the initial state of the residual flux in the transformer core C)       Several times the steady-state magnetizing current depending upon the initial state of the residual flux in the transformer core D)      Twice the steady-state magnetizing curre

Important Multiple Choice Questions in Electrical Machines 1.        A single phase transformer when supplied from 220V, 50 Hz has eddy current loss of 50 W. If the transformer is connected to a voltage of 330V, 50 Hz, the eddy current loss will be A)      168.75 W B)       112.5 W C)       75 W D)      50 W 2.        A coil wound on magnetic core is excited from an AC voltage source. The source voltage and its frequency are both doubled. The eddy current loss in the core will become A)      Half B)       Remains same C)       Double D)      Four times 3.        Building steel core out of stampings reduces eddy current loss because it A)      Increases core resistivity B)       Increases the effective length of eddy currents paths thereby increasing effective resistance to the flow of eddy currents C)       Increases core permeability D)      Reduces the effective length of eddy current path, thereby reducing effective resistance to the flow of eddy cu

Important Multiple Choice Questions in Electrical Machines 1.        In an electromechanical energy conversion device, the developed torque depends upon A)      Stator field strength and torque angle B)       Stator field and rotor field strengths C)       Stator field and rotor field strengths and the torque angle D)      Stator field strength only 2.        Consider the following statements: The use of interpoles in dc machines is to counteract the                                 I.             Reactance voltage                               II.             Demagnetizing effect of armature mmf in the commutating zone                             III.             Cross-magnetizing effect of armature mmf in the commutating zone Which of these statement(s) is/are correct? A)      1 &2 B)       2&3 C)       1&3 D)      3 alone 3.        The current drawn by a 220V DC motor of armature resistance 0.5 ohm and back emf 200V is A)      40A

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 an RC differentiating circuit with R=5kΩ and C=4 μF. The maximum output voltage is A)      0.2 V B)       2 V C)       10V D)      50 V 4.        The reciprocal of a network function is A)      An immittance function, if the original function is an omittance function

Important multiple choice questions in Power systems 1.        The good effect of corona on overhead lines is to A)      Increase the line carrying capacity due to conducting ionized air envelop around the conductor B)       Increase the power factor due to corona loss C)       Reduce the radio interference from the conductor D)      Reduce the steepness of surge fronts 2.        The principal information obtained from load flow studies in a power system are                                             I.             Magnitude and phase angle of the voltage at each bus                                           II.             Reactive and real power flows in each of the lines                                         III.             Total power loss in the network                                         IV.             Transient stability limit of the system Select the correct answer using the codes given below: A)      1 and 2 B)       3 and 4 C)