Description : The induced current in transformer which produced in the direction perpendicular to flux, is known as: a. Conventional current b. electronic current c. Perpendicular current d. Eddy current
Last Answer : c. Perpendicular current
Description : 69 In case there are burrs on the edges of the laminations of the transformer, it is likely to result in A. Vibrations B. Noise C. Higher eddy currents loss D. Higher hysteresis loss
Last Answer : C. Higher eddy currents loss
Description : 19 Transformer cores are built up from laminations rather than from solid metal so that A. Oil penetrates the core more easily B. Eddy current loss is reduced C. Less lamination is required for the windings D. Turn ratio is higher than voltage ratio
Last Answer : B. Eddy current loss is reduced
Description : To construct a step down transformer, the condition is: a. Ns > Np b. Np > Ns c. Np = Ns d. Np . Ns = 1
Last Answer : c. Np = Ns
Description : 43 The purpose of providing an iron core in a transformer is to A.Provide support to windings B. Reduce hysteresis loss C. decrease the reluctance of the magnetic path D. reduce eddy current losses
Last Answer : C. Decrease the reluctance of the magnetic path
Description : Brush sparking during commutation may be caused by ________. A. eddy currents in the armature core B. laminations in the generator field pieces C. induced current opposite to coil inductance D. coil inductance discharge occurring at commutation
Last Answer : Answer: D
Description : In the heating process of the ________type a simple method of temperature control is possible by means of a special alloy which loses its magnetic properties at a particular high temperature and regains ... ) core type induction furnace (C) coreless induction furnace (D) high frequency eddy current
Last Answer : Ans: D Magnetic property of alloy changes with change of the temperature and Heat is produced due to eddy current = i2R and i α f2
Description : Transformer cores are laminated to reduce _____________. A. eddy currents B. secondary flux C. leakage flux D. all of the above
Last Answer : Answer: A
Description : The harmonic currents in a power transformer does not cause increase in: a) Secondary voltage b) Core loss c) Copper loss d) Magnetic interference with protective relays
Last Answer : Ans: A
Description : Reversing the current flow through a coil will ___________. A. reduce the amount of flux produced B. have no effect on the eddy currents produced C. reduce the power consumed D. reverse its two-pole field
Description : The application of mutual induction is: a. TV b. Radio c. Transformer d. Motor
Last Answer : c. Transformer
Description : Which one of the following phenomena can be studied with -rays a) Photoelectric effect b) Compton effect c) Pair production d) All of the above
Last Answer : a) Photoelectric effect
Description : Which of the following phenomena provides a convincing proof for wave nature of radiation a) Reflection b) Refraction c) Polarization d) Interference and diffraction
Last Answer : d) Interference and diffraction
Description : The phenomena of pair production occurs only when the energy of incident photon is least equal a) 10.2 MeV b) 1.02 MeV c) 1.02 eV d) 0.102 MeV
Last Answer : b) 1.02 MeV
Description : The phenomena of induced emf was observed by Faraday and Henry in: a. 1931 b. 1831 c. 1535 d. 1940
Last Answer : a. 1931
Description : 8 The transformer core is laminated to A. Reduce the copper losses B. Reduce the core losses C. Reduce the eddy current losses D. None of the above
Last Answer : C. Reduce the eddy current losses
Description : The loss of energy over each A.C cycle magnetization and demagnetization of transformer, is called: a. Magnetization loss b. Hysteresis loss c. Demagnetization loss d. energy loss
Last Answer : c. Demagnetization loss
Description : A transformer: a. Works on A.C. only b. Works on D.C only c. Works on A.C. and D.C d. Has no hysteresis loss
Last Answer : a. Works on A.C. only
Description : Which of the following losses is/are present in every direct current generator armature? A. Winding copper loss B. Core eddy current loss C. Magnetic hysteresis loss D. All of the above.
Description : A ferrite core has less eddy current loss than an iron core because ferrites have (A) High resistance. (B) Low resistance. (C) Low permeability. (D) High hysteresis.
Last Answer : (A) High resistance.
Description : A ferrite core has less eddy current loss than an iron core because?
Last Answer : A ferrite core has less eddy current loss than an iron core because ferrites have high hysteresis.
Description : When a transformer is used to step down voltage, the low voltage winding is _____________. A. part of the core B. the primary coil C. not insulated D. the secondary coil
Description : A transformer steps down 220V to 40 volts. If the secondary turns are 40 then primary turns will be: a. 20 b. 40 c. 120 d. 220
Last Answer : d. 220V
Description : A rainbow is produced when sunlight falls on drops of rain. Which of the following physical phenomena is responsible for this? 1. Diffusion 2. Refraction 3. Internal reflection (a) 1, 2 and 3 (b) 1 and 2 (c) 2 and 3 (d) 1 and 3
Last Answer : Ans:(c)
Description : What is Eddy current loss in transformer?
Last Answer : In transformer, we supply alternating current in the primary, this alternating current produces alternating magnetizing flux in the core and as this flux links with secondary winding, there will be induced ... dissipated as heat. This type of energy loss is called eddy current loss of transformer.
Description : 9 Which loss is not common between a transformer and rotating machines? A. Eddy current loss B. Copper loss C. Windage loss D. Hysteresis loss
Last Answer : A. Eddy current loss
Description : 24 Transformer cores are laminated in order to A. simplify its construction B. minimise eddy current loss C. reduce cost D. reduce hysteresis loss
Last Answer : B. Minimise eddy current loss
Description : 17. Which type of loss is not common to transformer and rotating machines? A. Eddy current loss B. Copper loss C. Hysteresis loss D. Windage loss
Last Answer : D. Windage loss
Description : A 220/440 V, 50 Hz, 5 KVA, single phase transformer operates on 220V, 40Hz supply with secondary winding open circuited. Then (A) Both eddy current and hysteresis losses decreases. (B) Both ... same but hysteresis loss increases. (D) Eddy current loss increases but hysteresis loss remains the same.
Last Answer : (A) Both eddy current and hysteresis losses decreases.
Description : A transformer at 25 Hz develops 20 W hysteresis loss and 50 W eddy current loss. If the applied voltage and frequency are doubled, the new core losses are (A) 140 W (B) 180 W (C) 240 W (D) 480 W
Last Answer : A transformer at 25 Hz develops 20 W hysteresis loss and 50 W eddy current loss. If the applied voltage and frequency are doubled, the new core losses are 240 W
Description : [53] The iron loss of the transformer is negligible during short circuit test because A. The entire input is just sufficient to meet Cu losses only B. Flux produced is a small fraction of the normal flux C. Iron core becomes fully saturated D. Supply frequency is held constant
Last Answer : B. Flux produced is a small fraction of the normal flux
Description : If overloading a DC machine becomes necessary in an emergency, you should ____________. A. cool the machine with portable blowers and fans B. hold thermal overload relays open with blocks of ... the windings for cooling D. increase the residual magnetism value of windings to reduce eddy currents
Description : On tank vessels with an electrically-driven capstan, the motor should be meggered periodically to test _____________. A. insulation resistance B. eddy currents C. capacitance D. armature reactance
Description : Diamagnetic materials are magnetised (A) Strongly (B) Only slightly (C) With eddy currents only (D) In a direction opposite to that of the applied field
Last Answer : (D) In a direction opposite to that of the applied field
Description : Currents that flow in circles inside a disc are known as A. eddy currents B. circular currents C. air currents D. alternating curent
Last Answer : eddy currents
Description : Diamagnetic materials (A) Are magnetised by eddy currents only (B) Are non-magnetic and cannot be magnetised (C) Are magnetised in direction opposite to the magnetic field (D) Can be magnetised in one direction only
Last Answer : (C) Are magnetised in direction opposite to the magnetic field
Description : Eddy currents are induced in the pole shoes of a D.C. machine due to?
Last Answer : Eddy currents are induced in the pole shoes of a D.C. machine due to relative rotation between field and armature.
Description : The left hand rule correlates to (a) current, induced e.m.f. and direction of force on a conductor (b) magnetic field, electric field and direction of force on a conductor (c) self induction, ... and direction of force on a conductor (d) current, magnetic field and direction of force on a conductor
Last Answer : (d) current, magnetic field and direction of force on a conductor
Description : What are the differences between synchronous and induction motor?*
Last Answer : Synchronous motor : Constant speed on all loads, can be operated on a wide range of power factors, not self starting, requires dc excitation.
Description : How is the speed of a 3-phase induction motor varied?
Last Answer : The speed of a normal 3-phase induction motor is a function of the frequency of the supply voltage. Changing the speed of such a motor hence requires building a 3-phase power frequency ... realised by using power MOSFETs (or IGBTs) capable of handling high voltages and fast switching speeds.
Description : What is an induction motor?
Last Answer : An induction motor is an alternating current motor in which the primary winding on one member (usually the stator) is connected to the power source and a secondary winding or a squirrel-cage secondary winding on the other member (usually the rotor) carries the induced current
Description : The principle of AC generator is: a. Mutual induction b. self induction c. electromagnetic induction d. Induction
Last Answer : b. self induction
Description : The phenomenon of producing emf in the coil due to change of current in the coil itself is called: a. mutual induction b. self-induction c. self-inductance d. mutual inductance
Last Answer : d. mutual inductance
Description : A proton beam moves towards an observer. The direction of magnetic induction is a) towards right b) anticlockwise c) towards left d) clockwise
Last Answer : d) clockwise
Description : The reflective index numberis a. anumberwhichcomparesthe transparencyof amaterialwiththatof air b. a number assigned by the manufacturer to the fiber in question c. a number which determines the core diameter d. a term for describing core elasticity
Last Answer : a. anumberwhichcomparesthe transparencyof amaterialwiththatof air
Description : The claddingwhichsurroundsthe fiber core a. is used to reduce optical interference b. is used to protect the fiber c. acts to help guide the light in the core d. ensures that the refractive index remains constant
Last Answer : c. acts to help guide the light in the core
Last Answer : The purpose of providing iron core in a step-up transformer is to decrease the magnitude of magnetizing current.
Description : The transfer function of a system is 10/(1+s) when operating as a unity feedback system, the steady state error to a step input will be a) 0 b) 1/11 c) 10 d) Infinity
Last Answer : Ans: 1/11
Description : To couple a coaxialline toa parallel-wire line,itisbesttouse a a. slotted line b.balun c. directional coupler d. quarter-wave transformer
Last Answer : b.balun
Description : What is a current transformer and voltage transformer?*
Last Answer : In electrical engineering, a current transformer (CT) is used for measurement of electric currents. Current transformers, together with voltage transformers (VT) (potential transformers (PT)), ... transformers are commonly used in metering and protective relays in the electrical power industry.