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It is B-H curve of magnetic material, it shows retetivity,coercivity & other propert of magnetic matetial like Iron
It helps in choosing the material for designing of rotor poles
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Description : State Magneto-striction. Draw Hysteresis loop for : (i) High silicon steel (ii) Copper (iii) Soft iron (iv) Wood

Answer : Magneto-striction: It is the change in dimensions of ferro magnetic material when it is magnetized for eg. Silicon steel, iron or any ferromagnetic material.  i) Hysteresis loop for High silicon steel :  ... loop for Soft iron :  iv) Hysteresis loop for Copper and Wood : 

Description : Draw B-H curve for magnetic material and state its nature. State the significance of hysteresis loop. Also draw the hysteresis loop for hard steel and soft steel. 

Answer : B-H curve for magnetic material: The B-H curve is the graphical representation of relation between flux density (B) and applied field strength (H), with H plotted on the x-axis and B plotted on ... or crossing an air gap tends to bulge outwards the iron ring, this effect is called as Fringing .

Description : Draw Hysteresis loop for Hard steel and soft steel. Also write one application of each material.

Answer : Application of Hard steel:  Fig. (a) Shows hysteresis loop for hard steel. Such materials are used for producing permanent magnets. Such a hysteresis loop represents a large residual ... Residual flux & coercive force are less. Hence material can be used for making the electromagnets. 

Description : Explain the hysteresis loop of a magnetic material with neat diagram.

Answer : Hysteresis loop of magnetic material:  The circuit arrangement for plotting the hysteresis loop is shown in figure given below. The electromagnetic part consists of a coil wound on the iron ring ... one magnetic reversal is called hysteresis loop. Meaning of hysteresis is to lag behind.

Description : The hysteresis loop of magnetic material has an area of 5 cm2 with the scales given as 1 cm=2AT and 1 cm=50 mWb, at 50 Hz, the total hysteresis loss is  (A) 15 W (B) 20 W (C) 25 W (D) 50 W 

Description : If the area of hysteresis loop of a material is large, the hysteresis loss in this material will be?

Answer : If the area of hysteresis loop of a material is large, the hysteresis loss in this material will be large.

Description : Hysteresis Loop

Description : What is magnetic hysteresis?

Answer : Magnetic Hysteresis: When the magnetic material is subjected to a cycle of magnetization and demagnetization for both the directions of the current, then it is found that flux density B in ... material lags behind the applied magnetizing force H. This phenomenon is known as magnetic hysteresis.

Description : What is magnetic hysteresis? What is the cause of hysteresis?

Answer : Magnetic hysteresis: When a magnetic material is subjected to cycle of magnetization, it is found that flux density (B) in the material lags behind applied magnetizing force (H). This ... the movement of orientation, due to which the flux density lags behind the magnetic field intensity.

Description : What is the difference between eddy current and hysteresis loss?

Answer : Loss occurred by magnetising and demagnetising process is called histerisis loss and the current flowed due to the magnetic field produced by the electric field applied is called eddy current losses

Description : Explain hysteresis effect in instrument

Answer : Phenomena which depicts different output effects when loading and unloading an instrument by any form of energy. It is due to the fact that all the energy put into the stressed parts when loading is not recoverable upon unloading. 

Description : Define : i) Hysteresis ii) Drift

Answer : i. Hysteresis: Hysteresis is due to magnetic effects of the metals. It gives the relation between field current and the output voltage. The magnetization of ferromagnetic substances due to a varying magnetic field ... the true value of the variable does not change is referred to as drift.

Description : State the factors affecting hysteresis loss.

Answer : i) Flux density ii) Frequency iii) Volume of the magnetic material iv) Nature of magnetic material

Description : Hysteresis losses in electrical machines is equal to a. B1.2max f b. B1.6max f c. B1.2min f d. B1.2max fmin 

Answer : Hysteresis losses in electrical machines is equal to a. B1.2max f b. B1.6max f c. B1.2min f d. B1.2max fmin 

Description : Hysteresis is commonly found in ______ A) ferromagnetic materials B) ferroelectric materials C) both A and B D) none of these

Answer : Hysteresis is commonly found in ______ A) ferromagnetic materials B) ferroelectric materials C) both A and B D) none of these

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

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 : Hysteresis and eddy current loss are used in (1) Induction heating of steel (2) Dielectric heating (3) Induction heating of brass (4) Resistance heating 

Description :  Hysteresis loss in a transformer depends upon: -  a) both voltage and frequency b) voltage alone c) frequency alone d) none of these

Answer :  Hysteresis loss in a transformer depends upon: - both voltage and frequency

Description : A hysteresis motor:  (A) is not self-starting in nature (C) needs dc excitation for starting (B) is a constant speed motor (D) can not be run in reverse direction

Answer : A hysteresis motor: is a constant speed motor 

Description : Principle of hysteresis is not used in  (a) electrical water geyser (b) electrical motor (c) multi-vibrators (d) Schmitt trigger

Description : The direction of rotation of hysteresis motor is determined by the:  (A) Resistivity of the rotor material. (B) Amount of hysteresis loss. (C) Permeability of rotor material. (D) Position of shaded pole w.r.t main pole. 

Description : In a magnetic material hysteresis loss takes place primarily due to?

Answer : In a magnetic material hysteresis loss takes place primarily due to it high retentivity.

Description : What are the disadvantages of Open loop control system?

Answer : Open loop control system are less reliable. In open loop control system Optimization is not possible. Open loop control system are less accurate.

Description : (i) Bilateral Network (ii) Node (iii) Loop (iv) Branch

Answer : (i) Bilateral Network: If the characteristic of network (response or behavior) is independent of the direction of current through its elements in it, then the network is called as a bilateral network e. ... A part of an electric network which lies between two junctions or nodes is known as branch. 

Description : Write the application of the following antennas: 1) Rectangular antenna 2) Dish antenna 3) Horn antenna 4) Loop antenna 5) Yagi-Uda antenna. 

Answer : Applications:  1.Rectangular antenna  i)Used in Mobile and satellite communication ii)Used in Global Positioning System iii) Used for Radio Frequency Identification (RFID) iv) Radar  Dish ... antenna. 2. Yagi-Uda antenna is used in conditional Access System (CAS) at the decryptor.

Description : Explain how sinusoidal AC voltage is generated by using simple one loop generator.

Answer : An electric current produced by means of electrical machine is known as generator which converts mechanical energy into electrical energy. When conductor cuts the magnetic flux, emf induced in it. (Faraday' ... upon position of armature. The nature of emf is alternating as shown by the waveform. 

Description : Define the terms : i) Node ii) Branch iii) Loop iv) Mesh

Answer : i) Node:  A point or junction where two or more elements of the network are connected together is called as node.  ii) Branch: A part of an electric network which lies between two junctions ... path (same as loop) in an electric circuit. OR A loop that does not contain any other loop inside

Description : Define- (i) Node (ii) Loop for a DC circuit

Answer : Ans: i) Node: A point or junction at which two or more elements of network are connected is called as node. ii) Loop: A closed path for flow of current in an electrical circuit is called loop.

Description :  The number of loop equations required to completely analysing a network comprising of 8 independent branches and 6 nodes including the reference node shall be A) 3 B) 2 C) 4 D) 5 

Answer :  The number of loop equations required to completely analysing a network comprising of 8 independent branches and 6 nodes including the reference node shall be 3 

Description : A negative feedback loop returning a voltage to the input raised the input impedance and making the circuit a better

Answer : A negative feedback loop returning a voltage to the input raised the input impedance and making the circuit a better voltage sensor

Description : A system has 14 poles and 2 zeros in its open -loop transfer function. The slope of its highest frequency asymptote in its magnitude plot is (a) - 40 dB/dec (b) - 240 dB/dec (c) + 40 dB/dec (d) + 240 dB/dec

Answer : A system has 14 poles and 2 zeros in its open -loop transfer function. The slope of its highest frequency asymptote in its magnitude plot is (a) - 40 dB/dec (b) - 240 dB/dec (c) + 40 dB/dec (d) + 240 dB/dec

Description : An OP amp has an open loop gain of 1,00,000. If the feedback fraction is 0.02, the approximate closed loop gain is (a) 1 (b) 1,00,000 (c) 50 (d) 0.02

Answer : The closed loop gain Ag = G/(1+G*f) Where G is the open loop gain and f is the feedback fraction  So Ag = 49.975

Description : For a closed loop controlled d.c. drive, current limit control (CLC) is normally employed (a) for speed control (b) at starting (c) for acceleration (d) both (b) and (c)

Description : Addition of a pole to the open loop transfer function has the effect of (A) Pulling the root locus to the left (B) Pulling the root locus to the right (C) Either (A) or (B) (D) Does not have any effect on the root locus

Description : If the conductive loop on the rotor of a simple two -pole, single-phase generator rotates at the rate of 400 rps. The frequency of the induced output voltage will be: A. 40 Hz B. 100 Hz C. 400 Hz D. indeterminable

Answer : If the conductive loop on the rotor of a simple two -pole, single-phase generator rotates at the rate of 400 rps. The frequency of the induced output voltage will be: 400 Hz

Description :  Open loop control system is one in which the control action :  a) Depends on the input signal b) Is independent of the desired output c) Depends on system variables d) Depends on system size

Answer :  Open loop control system is one in which the control action : Is independent of the desired output

Description : Varley loop tests are preferred over Murray loop tests because  (1) Valley loop test can locate open circuit fault (2) Varley loop test gives higher accuracy (3) in Varley loop test provision is made for ... of obtaining it from the relation R = pl/a (4) Valley loop test can locate the earth fault

Description : An open-loop system is better than a closed-loop system in terms of   (a) Accuracy (b) Stability (c) Noise reduction (d) Sensitivity  

Description : If the characteristics equation of a closed loop system is s2+2s+2=0, then the system is  (A) Over damped (B) Critically damped (C) Under damped (D) Undamped 

Answer : C. Solving the above character equation gives complex roots -1+i and -1-i. If we plot that roots on real and imaginary axis plane(s-plane), it will be completely on left side of s-plane. So, the oscillations of the above conjugate roots are underdamped and are absolutely stable.

Description : An electromechanical closed -loop control system has the transfer function C(s)/R(s) = k/s (s2 + s +1) (s+ 4) +k. Which one of the following is correct?  (A) The system is stable for all positive ... values of k between zero and 3.36 (D) The system is stable for values of k between 1.6 and 2.45 

Description : Which of the following is an example of an open loop system ? (A) Household refrigerator (B) Respiratory system of an animal (C) Stabilisation of air pressure entering into a mask (D) Execution of a program by a computer

Description : Magnetic Hysteresis

Description : Describe with neat sketch working of hysteresis motor.

Answer : Working: When stator is energized with single phase ac supply, rotating magnetic field is produced because of starting (auxiliary) and main windings, which remain in circuit permanently. The ... the principle of magnetic locking this motor either rotates at synchronous speed or not at all.

Description : For heating a magnetic material using induction heating, the hysteresis and eddy current losses are respectively proportional to (a) f and f 2 (b) f 2 and f (c) f and f (d) none of the above 

Description : The hysteresis and eddy current losses of a single phase transformer working on 200 V, 50 Hz supply are Ph and Pe respectively. The percentage decrease in these when operated on a 160 V, 40 Hz supply are   (a) 32, 36 (b) 20, 36 (c) 25, 50 (d) 40, 80 

Answer : The hysteresis and eddy current losses of a single phase transformer working on 200 V, 50 Hz supply are Ph and Pe respectively. The percentage decrease in these when operated on a 160 V, 40 Hz supply are 20, 36

Description : The term hysteresis is associated with (A) On-Off control (B) P-I control (C) Feed forward control (D) Ratio control

Answer : The term hysteresis is associated with On-Off control

Answer : No eddy current and hysteresis losses occur in Electrostatic instruments.

Answer : Hysteresis of an instrument means: The change in the same reading when input is first increased and then decreased.

Answer : The rotor of a hysteresis motor is made of chrome steel.

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