Description : Materials subjected to rapid reversal of magnetism should have (a) large area oiB-H loop (b) high permeability and low hysteresis loss (c) high co-ercivity and high retentivity (d) high co-ercivity and low density
Last Answer : (b) high permeability and low hysteresis loss
Description : Those materials are well suited for making permanent magnets which have _____ retentivity and _______ coercivity.
Last Answer : Those materials are well suited for making permanent magnets which have high retentivity and high coercivity.
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 : The materials having low retentivity are suitable for making (a) weak magnets (b) temporary magnets (c) permanent magnets (d) none of the above
Last Answer : (b) temporary magnets
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 : How often should you demagnetize a recorder's magnetic heads?
Last Answer : Every 8 to 25 hours depending on the manufacturer's recommendations.
Description : What type of equipment should you use to demagnetize your recorder's magnetic heads?
Last Answer : A hand-held degausser like the manual degaussers used for degaussing magnetic tape.
Description : Draw BH Curve and define coercivity and reluctivity.
Last Answer : BH Curve: Definitions: Coercivity: For ferromagnetic material the coercivity is the intensity of the applied magnetic field required to reduce the magnetization of that material to zero after the ... to the ratio of intensity of the magnetic field to the magnetic induction of the material.
Description : The energy required to completely remove an electron from the first Bohr orbit is called a) excited energy b) ionization energy c) accelerated energy d) orbital energy
Last Answer : b) ionization energy
Description : The minimum energy required to eject an electron from a metal surface is called a) Intensity b) Threshold frequency c) Work function d) Photo energy
Last Answer : c) Work function
Description : The amount of energy required to completely remove an electron from the first Bohr orbit is a) 13.6 MeV b) 13.6 eV c) 1.36 MeV d) 1.36 eV
Last Answer : b) 13.6 eV
Description : How do you magnetize something made of ironcobalt or nickle?
Last Answer : Feel Free to Answer
Description : In replacing a defective transformer with a new one, which of the following actions must be carried out to insure proper operation of the equipment it serves? A. The secondary leads must be grounded ... magnetize it. D. The iron core must be grounded for 10 minutes to remove any residual magnetism.
Last Answer : Answer: B
Description : What equipment should you use to de-magnetize a magnetic tape transport?
Last Answer : A hand-held degausser.
Description : How to Magnetize Metal
Last Answer : How to Magnetize Metal We're usually familiar with magnets in the form of clunky metal already magnetized. Not a lot of people know that you can actually make more magnets from existing magnets. ... magnetize other metallic objects. As long as the battery life holds, the nail will remain magnetized.
Description : Which of these materials requires the least value of magnetic field strength to magnetize it? a. Nickel b. Silver c. Tungsten d. Sodium chloride
Last Answer : Which of these materials requires the least value of magnetic field strength to magnetize it? a. Nickel b. Silver c. Tungsten d. Sodium chloride
Description : What is retentivity?
Last Answer : The ability of a material to retain magnetism
Last Answer : The retentivity (a property) of material is useful for the construction of permanent magnets.
Last Answer : The materials having low retentivity are suitable for making temporary magnets.
Description : The unit of retentivity is?
Last Answer : The unit of retentivity is weber/sq. m.
Description : The minimum frequency required to eject electrons from a metallic surface is called a) Critical frequency b) Peak value of frequency c) Threshold frequency d)Photo frequency
Last Answer : c) Threshold frequency
Description : Loss comparisons between fusionsplices andmechanicalsplices are a. 1:10 b. 10:1 c. 20:1 d. 1:20
Last Answer : a. 1:10
Description : Thegroundwave eventuallydisappears, as onemoves awayfromthetransmitter, because of a. interference from the sky wave b. loss of line-of-sight conditions c. maximumsingle-hop distance limitation d. tilting
Last Answer : d. tilting
Description : Eddy currents produced in the core of transformer are responsible for: a. heat loss b. Step up process c. Step down process d. induction phenomena
Last Answer : d. induction phenomena
Description : The termresponsivityasit appliesto a light detectorisbest described as a. the time required for the signal to go from 10 to 90 percent of maximum amplitude b.the ratio ofthediode output currentto ... of output current to output power d. the ratio of output current to input current
Last Answer : b.the ratio ofthediode output currentto opticalinputpower
Description : VLFwaves are used forsome type ofservices because a. of the low powers required b. the transmitting antennas are of convenient size c. they are very reliable d. the penetrate the ionosphere easily
Last Answer : c. they are very reliable
Description : What are the test and measuring instrument required in an Electrical depots?
Last Answer : Ans. Following are the test and measuring instruments required in an Electrical depots. a. Test lamp b. Line Tester c. Continuity tester d. Volt meter e. Ammeter f. Earth megger g. Megger h. Lux meter i. Power analyzer j. Infrared thermometer
Description : The loss of strength in compression which occurs, when there is a gain of strength in tension due to over loading is called (A) Bauschinger effect (B) Hooke's effect (C) Hysteresis (D) Relaxation
Last Answer : (A) Bauschinger effect
Description : What is Hysteresis Loss ?
Last Answer : We know that transformers are made of electromagnetic materials like iron , ferrite cores etc. Now when this transformer is repeatedly magnetized and de-magnetized by an alternating current, the ... , generators , fans. However, generators and transformers try to control this hysteresis loss.
Last Answer : Hysteresis Loss Wh = nh / B ^ 1.6 max fv
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.
Last Answer : Answer: D
Description : Materials that retain a large part of their magnetization, after the magnetizing force is removed, are said to have _____________. A. low hysteresis loss B. high flux density C. high permanence D. high permeability
Last Answer : Answer: C
Description : As an armature revolves within a magnetic field, friction is developed between the rotated magnetized particles as they pass through each magnetization cycle. This results in ____________. A. copper loss B. eddy-current loss C. hysteresis loss D. armature reaction
Description : The heating of conductors as a result of resistance in a distribution circuit causes a power loss expressed as _____________. A. line droop B. line loss C. IR drop D. hysteresis
Description : Mention the factors on which hysteresis loss depends?
Last Answer : (i) Quality and amount of iron in the core (ii) Flux density and (iii) Frequency.
Description : How to minimize Hysteresis loss?
Last Answer : By using good magnetic material. By using less value of Magnetic flux density
Description : What is hysteresis loss in transformer?
Last Answer : The magneto motive force or mmf applied in the transformer core is alternating. For every cycle due to this domain reversal, there will be extra work done. For this reason, there will be a consumption of electrical energy which is known as Hysteresis loss of transformer.
Description : Straight silicon steel (containing Si from 0.5 to 5%) because of their low hysteresis loss and high magnetic permeability are used for electrical appliances. Which of the following electrical ... /generators (B) Generators and small motors (C) Induction motors (D) High frequency transformers
Last Answer : (D) High frequency transformers
Description : 70] Silicon steel used in laminations mainly reduces A. Hysteresis loss B. Eddy current losses C. Copper loss D. All of the above
Last Answer : A. Hysteresis loss
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 : 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 : 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 : Hysteresis loss least depends on (A) Frequency. (B) Magnetic field intensity. (C) Volume of the material. (D) Grain orientation of material.
Last Answer : (D) Grain orientation of material.
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 : The armature of a dc machine is laminated to reduce: (A) Eddy current loss (B) Hysteresis loss (C) copper losses (D) friction and windage losses
Last Answer : Ans: A Thinner the laminations, greater is the resistance offered to the induced e.m.f., smaller the current and hence lesser the I2R loss in the core.
Description : Which of the following properties is not necessarily desirable in the material for transformer core? A. Mechanical strength B. Low hysteresis loss C. High thermal conductivity D. High permeability
Last Answer : C) high thermal conductivity
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 : State the factors affecting hysteresis loss.
Last Answer : i) Flux density ii) Frequency iii) Volume of the magnetic material iv) Nature of magnetic material