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How eddy currents are generated?

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Description : Eddy currents are induced in the pole shoes of a D.C. machine due to?

Answer : Eddy currents are induced in the pole shoes of a D.C. machine due to relative rotation between field and armature.

Description : List at least two examples that show how static electricity can be generated.

Answer : Examples of how static electricity can be generated include combing your hair, walking across a carpeted room, or sliding two pieces of plastic across each other.

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 : The transient currents are associated with the?

Answer : The transient currents are associated with the changes in the stored energy in the inductors and capacitors.

Description : How eddy current can be minimized?

Description : How eddy current is produced in a transformer?

Answer : For handling greater currents induction wattmeters are used in conjunction with current transformers.

Description : State the types of radioactive waste generated in a nuclear power station. Explain the methods employed for their disposal.

Answer : Types of radioactive waste: The waste produced in nuclear power plant is in the form of solid, liquid & gases, 1. Solid Waste Disposal:-  Solid wastes removed from the reactor are very ... are measured. If it is safe then released to atmosphere at high level through large height chimney.

Answer : Electricity is generated at electrical power generation station.

Description : Why harmonics are generated in electrical system?

Description : Which of the following can reduce the Eddy current losses? A) By making the core of a stack of plates electrically insulated from each other B) By making the core of solid block C) By increasing the applied voltage  D) None of these

Answer : Which of the following can reduce the Eddy current losses? A) By making the core of a stack of plates electrically insulated from each other B) By making the core of solid block C) By increasing the applied voltage  D) None of these

Description : A ferrite core has less eddy current loss than an iron core because?

Answer : A ferrite core has less eddy current loss than an iron core because ferrites have high hysteresis.

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 : what is eddy current ?

Answer : In magnetic circuits when we supply current to coil which wound on some core( of iron cast iron, ferrite ) material it produce magnetic field but there is small amount of flux which also ... heat and losses in magnetic circuits..for good working conditions we always try to minimize eddy current

Description : Explain following techniques related to energy conservation in transmission and distribution system. (i) By balancing phase currents (ii) Variable technical losses (I2R losses).

Answer : (i) Balancing Phase currents: Proper (healthy balanced) three phase loads always draw equal currents in all lines but single phase loads in the 3 phase 4 wire system or loads connected between two ... . 11) Minimize I2R losses. 12) Balance the load currents. 13) Regulate the system voltages.

Answer : In a single phase power factor meter the phase difference between the currents in the two pressure coils is exactly 90°.

Answer : Interruption of large currents by relay requires arc suppressing blow out coils, wide separation of the opened contacts, high speed opening of contacts.

Description : In an alternator at lagging power factor the generated voltage per phase as compared to that at unity power factor?

Answer : In an alternator, at lagging power factor the generated voltage per phase as compared to that at unity power factor must be more than terminal voltage.

Description : Is electricity generated in AC or DC?

Answer : Electricity   is  generated  in  AC.

Description : Give two applications of each : 1) Eddy current sensor 2) Optical sensor.

Answer : Eddy current sensor : 1. Detection of non-magnetic but conductive materials. 2. Displacement sensing 3. Position sensing Optical sensor : 1. Position Detection 2. Velocity Detection 3. Acceleration Detection 4. Direction Detection

Description : The eddy current loss in a dc generator is 400 W at 40 Hz frequency of reversal and constant flux density. When frequency is increased to 50 Hz., eddy current loss is :  (A) 256 W (B) 320 W (C) 500 W (D) 625 W

Answer : The eddy current loss in a dc generator is 400 W at 40 Hz frequency of reversal and constant flux density. When frequency is increased to 50 Hz., eddy current loss is : 625 W

Description : Eddy current damping cannot be used for moving iron instrument because

Answer : Eddy current damping cannot be used for moving iron instrument because the presence of a permanent magnet required for such purpose would affect the deflection and hence the reading of the instrument

Answer : The disc of an instrument using eddy current damping should be of conducting and non-magnetic material.

Description : Explain hysteresis loss, eddy current loss and skin effect limitations with reference to magnetic material.

Answer : Hysteresis loss: Hysteresis loss is a loss which occurs due to the friction of magnetic domain due to the change in magnetic field in ferromagnetic material like iron. Hysteresis loss causes power loss ... loss in transformer is given by, We=Kef2Kf2Bm2watts Skin effect limitations:

Answer : By using diesel generator the power is generated in ships

Description : Write how energy can be stored or generated in each of following : i) solar cell ii) geothermal energy iii) hydrogen energy in biomass.

Answer : i) Solar cell : Energy can be stored:  1. Storage Battery is used to store electricity.  OR   Energy can be generated  1. Directly Conversion:   a) By use of P.V Cell ( ... fuels in engines:-  3. The biomass is subjected to fermentation process to obtain a gaseous fuel called biomass

Description : X1 is a 3D form generated from the shape X, using certain 3D operations. It has 14 surfaces in total. The same operations are carried out on shape Y. How many surfaces would the resulting 3D form have?

Answer : 20

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 : The transient currents are due to _____.

Answer : The transient currents are due to changes in stored energy in inductors and capacitance

Description : Alternating voltages and currents are represented by straight line with an arrow to represent the magnitude and direction. This representation is called

Answer : Alternating voltages and currents are represented by straight line with an arrow to represent the magnitude and direction. This representation is called Phasor quantity

Description : 1. How can Permanent hardness of water be removed? 2. The Sun City is located in which continent? 3. Which situation makes a firm most efficient? 4. On the shore of which counrty cold currents ... Aravalli ranges are an example of which mountains? 20. Which war was ended by the Treaty of Madras?

Answer : Answer : 1. By adding washing soda 2. South Africa3. Lowest average costs 4. Peru 5. Ramananda 6. Hydra 7. Dr. B. R. Ambedkar 8. Black 9. North-west Atlantic10. Gulbadan Begam 11. Bangladesh ... Rana Sanga 16. The Cabinet 17. Radio waves 18. Morarji Desai 19. Residual mountains 20. First Mysore war

Description : Two heater wires of equal length are connected first in series and then in parallel. The ratio of heat generated from series to parallel connection will be (a) 4 : 1 (b) 2 : 1 (c) 1 : 2 (d) 1 : 4

Description : Calculate the power loss, if power generated by two plants are P1=50 MW and P2 =40 MW and the loss coefficients are B11=0.001, B22=0.0025 and B12=-0.0005.  (A) 4.5 MW (B) 5.5 MW (C) 6.5 MW (D) 8.5 MW

Answer : A

Description : A current of 5 amps passes through a 10 ohm resistor. How many joules of energy will be generated by this resistor in 2 seconds? 

Answer : ANSWER: 500 JOULES

Answer : Eddy current

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 : Eddy current losses in transformer cores can be reduced by the use of  1. Solid cores  2. Laminated cores  3. Ferrites  Select the correct answer using the codes given below : (a) 2 and 3 only (b). 1 and 2 only (c) 1 and 3 only (d) 1, 2 and 3

Answer : Eddy current losses in transformer cores can be reduced by the use of  1. Solid cores  2. Laminated cores  3. Ferrites  Select the correct answer using the codes given below : (a) 2 and 3 only (b). 1 and 2 only (c) 1 and 3 only (d) 1, 2 and 3

Description : In moving iron instruments, eddy current damping cannot be used as  (a) They have a strong operating magnetic, field (b) They are not normally used in vertical position (c) They ... of a permanent magnet required for eddy current damping would distort the existing weak operating magnetic field

Answer : In moving iron instruments, eddy current damping cannot be used as The introduction of a permanent magnet required for eddy current damping would distort the existing weak operating magnetic field

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 : Compare AC & DC track circuits on i) Length of circuit ii) Application iii) Effect of stray currents. iv) Maintenance

Answer : Ans: i) Length of circuit - a) AC track circuit is having long length upto 3 to 5 km b) DC track circuit is having short length  ii)Application -a) AC track circuit is used ... ) Maintenance - a) AC track circuit has easier and cheaper maintenance b) DC track circuit has complicated maintenance 

Description : In delta connected load, the zero sequence currents (a) are absent (b) circulate locally (c) flow through phase wires (d) flow through earth wires 

Description : In applying superposition theorem, to determine branch currents and voltages   (a) all current and voltage sources are shorted. (b) only current sources are open circuited. (c) only voltage sources are shorted. (d) voltage sources are shorted and current sources are open circuited. 

Description : Which fault gives rise to symmetrical fault currents ?   (a) Single line to ground fault (b) Line to line fault (c) Double line to ground fault (d) Three phase fault

Description : Two infinitely long, parallel wires carry currents which are in opposite directions. The two wires: w) are attracted toward each other x) repel each other y) have no effect on each other.

Answer : ANSWER: X -- REPEL EACH OTHER

Description : Particulates (< 1 µm size) remaining suspended in air indefinitely and transported by wind currents are called (1) Mists (2) Fumes (3) Aerosols (4) Smoke

Answer : Aerosols

Description : Ocean currents are an example of (1) convection (2) conduction (3) insulation (4) radiation

Answer : convection

Description : Fishing grounds of the world are found in areas where (1) there are high tides (2) warm and cold currents meet (3) there are low tides (4) high stormy waves occur

Answer : warm and cold currents meet

Description : Tsunamis are cuased by (1) mixing of cold and warm currents (2) earthquakes (3) changes in sea level (4) volcanic eruption

Answer : earthquakes

Description : Two unpedauces given by Z1 = 10 + j5 and Z2 = 8 + j9 are joined in parallel and connected across a voltage of V = 200 + j0. Calculate the circuit current and branch currents. Draw the vector diagram.

Answer : Solution: Given, Z1=10+j5, Z2=8+j9, V=200+j0

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