[PDF Notes] What are Stimulating Effects of Inflation?

There is a great controversy among economists as to whether inflation promotes economic development. A group of economists, including Keynes, believe that inflation promotes economic development. The following are their arguments.

1. Increases Investible Profits:

Inflation redistributes income and wealth in favour of the entrepreneurial classes who have high propensity to save. With this redistribution, the profits and savings in the economy will increase.

The increased savings will be used for investment purposes which, in turn, will increase income, output and employment in the economy.

2. Creates Optimistic Conditions:

Inflation creates optimistic conditions m economy and provides fresh opportunities for new business activities, since, during inflation, costs rise less rapidly than the prices, profit margins go up tempting the businessmen to make more and more investments in new productive enterprises.

3. Stimulates Entrepreneurship:

Inflation encourages bold entrepreneurship and rewards investors at the expense of conservative savers and renters.

4. Inflation Tax:

Inflation tax or deficit financing (i.e., covering the budget deficit through printing new money) can provide adequate funds to the government for financing development programmes in under­developed countries.

In an underdeveloped country, where there is little scope for additional taxation due to low income of the people and public borrowing is limited due to low levels of saving, the government can resort to inflation tax to cover the deficit in the budget.

Highlighting the merits of inflation tax, Keynes said, “A government can live by this means when it can live by no other. It is the form of taxation which the public finds hardest to evade and even the weakest government can enforce, when it can enforce nothing else.

The burden of the tax is well spread, cannot be evaded, costs nothing to collect, and falls, in a rough sort of way, in proportion to wealth of the victim.”

5. Utilisation of Resources:

Inflationary increase in aggregate demand permits a fuller utilisation of manpower and other resources of the economy. This leads to the quicker achievement of the objective of full employment of country’s resources.

6. Increasing Demand for Money:

Monetary expansion through deficit financing is essential in the underdeveloped countries not only for mobilisation of resources and their fuller utilisations but also for meeting the continuously increasing demand for money during the early development phase in these countries:

(a) with a continuous increase in investment, aggregate output is likely to increase, thus necessitating a corresponding increase in money supply for transaction purpose,

(b) As the economy grows, the non- monetised sector is gradually transformed into the monetised sector, leading to an increase in the demand for money,

(c) A process of continuous economic development leads to a rise in incomes, thus increasing the demand for cash balances on the part of the public.

(d) Due to increasing foreign aid, the demand for money is likely to increase further.

7. A Necessary Cost:

Some inflationary rise in prices is a necessary consequence of the process of economic development, particularly in the initial stages of development.

In the initial stages of development, the supply of consumer goods does not increase as rapidly as the supply of money.

Thus, inflation becomes inevitable during economic development. In fact inflation and economic growth go together; inflation promotes economic growth and economic growth, in turn, results in inflation.

[12 Class] Se-ual Reproduction in Flowering Pants – Biology

SE-UAL REPRODUCTION IN FLOWERING PLANTS – Biology CBSE

FLOWER :-
it is the fascinating reproductive organ of angiosperms.
It consist of :-

  1. Calyx
  2. Corolla
  3. Androecium
  4. Gynoecium

PRE- FERTILISATION – STRUCTURES AND EVENTS :-

  • Hormonal and structural changes are initiated leading to differentiation and development of floral primordium.
  • Inflorescences are formed which bear floral buds and then flowers.
  • Androecium and Gynaecium differentiate and develop.

STAMEN :-
—>  Stamen consist of

  1. Anther – terminal bilobed structure
  2. Filament – long slender stalk. Proximal end of the filament is attached to the thalamus or

petal.

STRUCTURE OF ANTHER :-

  •   Anther has two lobes (bilobed). Each lobe consists of two theca. Hence it is dithecous.
  •   Anther is a tetragonal structure which consist of four microsporangia located two in each lobe.
  •   Microsporangium develops into pollen sacs.
  •   Pollen sacs run longitudinally and contain pollen grains.

STRUCTURE OF MICROSPOANGIUM :-
—>  A typical microsporangium appears circular in outline.

It is surrounded by 4 walls.

  1. Epidermis          –  protects and help in dehiscence of anther.
  2. Endothecium
  3. Middle layers
  4. Tapetum             – nourishes the developing pollen grain


SPOROGENOUS TISSUE :-
It is compactly arranged homogenous cells which are present at centre of each microsporangium when the anther is young.

MICROSPOROGENESIS :-

  • Process of formation of microspores from pollen mother cell through meiosis.
  • The cells of the sporogenous tissue/microspore mother cell (2n) meiotically divide to form microspores which are arranged in a cluster of 4 cells called MICROSPORE TETRAD.
  • When the anther matures and dehydrates, the microspore dissociate from each other and develop into pollen grains
  • Thousands of pollen grains formed inside a microsporangium- released with dehiscence of anther.

POLLEN GRAINS :-
Pollen grains are male gametophyte – spherical in shape.

STRUCTURE OF POLLEN GRAIN :-
Pollen grains are made of 2 layered Wall,

  1. Exine :- Made of sporopollenin- most resistant organic matter known,
  2. Intine :-

-Thin and continuous layer
– Made of cellulose and pectin
3. Germ pores
– apertures on exine where sporopollenin is absent
– forms pollen tube.
4. A plasma membrane surrounds cytoplasm of pollen grain.

MATURE POLLEN :-
—  A mature pollen consist of 2 cells with nucleus (Vegetative and Generative)

VEGETATIVE CELL

  • Bigger
  • Abundant food reserve
  • Large irregular nucleus
  • Responsible for the development of pollen grain

GENERATIVE CELL

  • Small
  • Involves in syngamy (fuse with an egg)
  • Dense cytoplasm and nucleus.

Effect of Pollen on Human :-

  • Pollen grains cause allergy and bronchial afflictions
  • Leading to chronic respiratory disorders like asthma, bronchitis Eg :- Parthenium (carrot grass)

POLLEN PRODUCTS :-

  • Rich in nutrient.
  • Pollen tablets and syrup

– food supplements
– claims to increase performance of athletes and race  horse.

Period of viability :-

  • Once shed the pollen grains have to land on the stigma before they lose viability if they have to bring about fertilization.
  • Period of viability depends on temperature and humidity. Example:- cereals takes 20 minutes and members of rosaceae, leguminoseae, solanaceae  take months.
  • Pollen grains stored by CRYOPRESERVATION.
  • Used in crop breeding programmes.

PISTIL, MEGASPORANGIUM AND EMBRYO SAC :-

GYNAECIUM – female reproductive part of flower

  •  Gynaecium with 1 pistil – Monocarpellary
  •  Gynaecium with more than 1 pistil – Multicarpellary
  •  Fused pistil – Syncarpous
  • Free pistil – Apocarpous.

PISTIL :-
Pistil consist of

  1. Stigma
  2. Style
  3. ovary
  • ovarian cavity
  • placenta

Ovules arise from placenta.

  • single ovule – wheat, paddy
  • Many ovules – papaya, water melons, etc.

MEGASPORANGIUM (OVULE) :-

  • —  Ovule is a small structure attached to placenta.
  • —  Funicle – stalk by which ovule is attached to placenta
  • —  Hilum – junction between ovule and funicle
  • —  Integuments – protective envelops
  • —  Micropyle – small opening at the tip of ovule into where pollen tube enters
  • —  Chalaza – basal part of ovule
  • —  Nucellus (2n)-mass of cells enclosed in integuments. Has abundant food reserve.

MEGASPOROGENESIS :-

  • —  Process of formation of megaspores from megaspore mother cells is called MEGASPOROGENESIS.
  • —  Megaspore mother cells divide meiotically to form 4 megaspore (haploid)
  • —   out of 4, only 1 megaspore is functional and forms gametophyte and the rest degenerate.

 FEMALE GAMETOPHYTE (EMBRYO SAC) :-

  • —  The embryo sac develops from the functional megaspore (n).
  • —  MONOSPORIC DEVELOPMENT:- formation of embryo sac from a single megaspore.

FORMATION OF EMRYO SAC :-

  • Nucleus of functional megaspore divides mitotically to form 2 nuclei which move to opposite poles forming 2-nucleate embryo sac.
  • Two more mitotic nuclear division results in 4-nucleate and later 8- nucleate stages of embryo sac.
  • Then cell wall is laid down leading to organization of female embryo sac.

STRUCTURE OF EMBRYO SAC :-

  • Egg apparatus – present at the micropylar end and consist of 2 synergids and 1 egg cell

Synergids have cellular thickenings at micropylar tip called FILIFORM APPARATUS – guides the pollen tube into the synergid

  • Antipodal – 3 cells present at chalaza end
  • Polar Nuclei – Large central cell.

POLLINATION :-

  • —  The transfer of pollen grains from anther to stigma of a pistil is called pollination.
  • —  Based on the source of pollen, pollination is of  3 types:-

– AUTOGAMY
– GEITONOGAMY
– XENOGAMY

1. AUTOGAMY :-

  • Transfer of pollen grains from anther to stigma of the SAME flower.

REQUIREMENT:-

  1. Synchrony in pollen release and stigma receptivity.
  2. Closeness of stigma and anther
    • Chasmogamous flowers- flowers with exposed anthers and stigma
    • Cleistogamous flowers-flowers which do not open at all
    • Cleistogamy is disadvantageous because there is no chance of variation.

Ex:- oxalis ,viola

2. GEITONOGAMY :-

    • —  Transfer of pollen grains from anther to stigma of another flower of the same plant.
    • —  Genetically similar

Example:- cucurbits

3. XENOGAMY :-

  • Transfer of pollen grains from anther to stigma of another flower of different plant
  • Genetically different pollen grains are brought to the stigma.

Agents of Pollination:
1)      Abiotic agents:
a)      Wind
b)      Water
2)      Biotic agents:
a)      Insects
b)      Birds
c)       Bats
d)      Reptiles
e)      Mammals

Adaptations in flowers for Pollination ::-

I. Wind Pollination :-

  • pollen  grains :– light, non- sticky, winged
  • anther :- well exposed
  • stigma :- large and feathery
  • flower :- one ovule, arranged as inflorescence

         Example : corn cob, cotton, date palm

II. Water Pollination :-
                   – Bryophytes, Pteridophytes, Algae

  • pollen grains : protected by mucilaginous covering

Ex : Fresh water plants- Vallisneria, Hydrilla
Sea grass- Zostera

Main features of wind and water pollinated plants :-
         – produce pollen grains in large no.
         – do not produce nectar

III. Insect Pollination :-
       – Flowers : large, colourful, fragrant, rich in nectar
       – Pollen grains : sticky
       – Stigma : sticky

Certain rewards to pollinators :-

  • nectar and (edible) pollen grains as foods
  •  provide safe place for laying eggs

Example : Amorphophallus, Yucca

Outbreeding Devices :-

Continued self – Pollination – Inbreeding depression :-

Ways to avoid Self-pollination :-
(i) Pollen release & stigma receptivity – not synchronised
(ii) Stigma and anther – placed at different positions
(iii) Self-incompatibility
(iv) Production of unise-ual flowers

Eg: castor, maize (prevents autogamy)
papaya (prevents autogamy & geitonogamy)

Pollen – Pistil Interaction :-
All events – from deposition of pollen on stigma till the pollen tube enters the ovuleis called     Pollen-pistil interaction.
•        Recognition of compatible pollen
•        Germination of pollen grains
•        Development of Male Gametophyte

Artificial Hybridization :-

  • Crossing diff varieties of species- hybrid individual- with desirable characters of the parent plants
  • desired pollen grains for pollination- stigma protected from contamination
  • Emasculation : removal of anther
  • Bagging : flower covered- bag made up of butter-prevent contamination of stigma from unwanted pollen

Bagged flower- attains receptivity – mature pollen grains- dusted on the stigma – rebagged – fruits allowed to develop

  • Double Fertilisation
  • Syngamy

– pollen tube releases male gametes into synergids
– fusion of 1 of male gametes and egg cell
– fusion of 2nd male gamete and polar nuclei =Triploid endosperm nucleus- PEN (Triple Fusion)
– PEN – now called Primary Endosperm Nucleus – Endosperm

Post- fertilization Events :-     
All events that occur in a flower, after double fertilization is called Post- fertilization events

Major events are :-
(i)            Development of endosperm
(ii)             Development of embryo
(iii)             Maturation of ovule into seed
(iv)             Maturation of ovary into fruit

Endosperm :-

†     Two types of endosperm development :
(i) Free nuclear type (common method)
(ii) Cellular type
†      Cells of endosperm– store food materials- used for developing embryo
†      Non – Albuminous / Non-Endospermic seeds- endosperm completely utilized – before maturation of seeds. Ex: pea
†      Albuminous / Endospermic seeds- a portion of endosperm remain in mature seeds. Ex: castor

Embryo :-
†     Embryogeny – early stages of embryo development
†      Zygote   à     Proembryo    à   Mature embyo (heart-shaped)

Embryo consists of:
– embryonal axis
– cotyledons
– plumule
– radicle

Monocotyledonous Seed :-
–          Scutellem = Cotyledon
–           Coleorrhiza: undifferentiated sheath covering radical & root cap
–           Coleoptile: sheath covering plumule

Seed :-
–          Fertilized and mature ovule develops into seed.

Seed consists of:
–          cotyledon(s)
–          embryonal axis
–          Seed coat – double layered – formed by integuments

  • Testa (outer coat)
  • Tegmen (inner coat)

–          Micropyle: – small o        pening on seed coat, it facilitates entry of H2O & O2 into seeds (for germination)
–          Hilum:- scar on seed coat
–          Seed     – Albuminous / Non-Albuminous
–          Perisperm : remnants of nucellus that is persistent. Ex: Black pepper
–          Dormancy:  state of inactivity

Advantages of Seeds :-

  • To plants

(i) Seeds – reserve food materials- nourish seedling
(ii) Seed coat- protection to young embryo
(iii) Seeds of large no of species –live for several years
(iv) Seeds – better adaptive strategies- dispersal to new habitats- better survival

  • To mankind

(i) used as food – throughout the year
(ii) seed – basis of agriculture

Fruit :-
–          True fruit : – Fruit formed from the ovary
–          Parthenogenesis:  If ovary transform to fruit without fertilization. Ex : Banana
–          Parthenocarpy – induced with gibberellins & auxins without fertilization.
–          False fruit: any part other than ovary- forms the fruit. Ex: Apple

Apomixis & Polyembryony  :-
Other modes of reproduction

Apomixis :-
–          Form of a se-ual reproduction- mimics se-ual reproduction- seed formed without fertilisation
–          Formation of apomictic seeds :
·         diploid cell (formed without meiosis) – develop into embryo without fertilization
·         cells of nucellus (2n) surrounding embryo sac- protrude into embryo sac – develop into embryos. Ex. Citrus and Mango.

Polyembryony :-
–          Occurrence of more than one embryo in a seed
–          Often associated with apomixes.  Ex: Citrus, groundnut

Top 300 Rectifiers & Converters Objective Questions and Answers

RECTIFIERS & CONVERTERS Questions and Answers

1. Which of the following are the applications of D.C. system ?
(a) Battery charging work
(b) Arc welding
(c) Electrolytic and electro-chemical processes
(d) Arc lamps for search lights
(e) All of the above

Answer: e

2. Which of the following methods may be used to convert A.C. system to D.C. ?
(a) Rectifiers
(b) Motor converters
(c) Motor-generator sets
(d) Rotary converters
(e) All of the above

Answer: e

3. In a single phase rotary converter the number of slip rings will be
(a) two
(b) three
(c) four
(d) six
(e) none

Answer: a

4. A synchronous converter can be started
(a) by means of a small auxiliary motor
(b) from AC. side as induction motor
(c) from D.C. side as D.C. motor
(d) any of the above methods
(e) none of the above methods

Answer: d

5. A rotary converter is a single machine with
(a) one armature and one field
(b) two armatures and one field
(c) one armature and two fields
(d) none of the above

Answer: a

6. A rotary converter combines the function of
(a) an induction motor and a D.C. generator
(b) a synchronous motor and a D.C. generator.
(c) a D.C. series motor and a D.C. generator
(d) none of the above

Answer: b

7. Which of the following is reversible in action ?
(a) Motor generator set
(b) Motor converter
(c) Rotary converter
(d) Any of the above
(e) None of the above

Answer: c

8. Which of the following metals is generally manufactured by electrolysis process ?
(a) Load
(b) Aluminium
(c) Copper
(d) Zinc
(e) None of the above

Answer: b

9. With a motor converter it is possible to obtain D.C. voltage only upto
(a) 200-100 V
(6) 600—800 V
(c) 1000—1200 V
(d) 1700—2000 V

Answer: d

10. Normally, which of the following is used, when a large-scale conversion from AC. to D.C. power is required ?
(a) Motor-generator set
(b) Motor converter
(c) Rotary converter
(d) Mercury arc rectifier

Answer: d

11. A rotary converter in general construction and design, is more or less like
(a) a transformer
(b) an induction motor
(c) an alternator
(d) any D.C. machine

Answer: d

12. A rotary converter operates at a
(a) low power factor
(6) high power factor
(c) zero power factor
(d) none of the above

Answer: b

13. In which of the following appUcations, direct current is absolutely essential ?
(a) Illumination
(b) Electrolysis
(c) Variable speed operation
(d) Traction

Answer: b

14. Which of the following AC. motors is usually used in large motor-generator sets?
(a) Synchronous motor
(b) Squirrel cage induction motor
(c) Slip ring induction motor
(d) Any of the above

Answer: a

15. In a rotary converter armature currents are
(a) d.c. only
(b) a.c. only
(c) partly a.c. and partly d.c.

Answer: c

16. In which of the following equipment direct current is needed ?
(a) Telephones
(b) Relays
(c) Time switches
(d) All of the above

Answer: d

17. In a rotary converter I2R losses as compared to a D.C. generator of the same size will be
(a) same
(b) less
(c) double
(d) three times

Answer: b

18. In a mercury arc rectifier positive ions are attracted towards
(a) anode
(b) cathode
(c) shell bottom
(d) mercury pool

Answer: b

19. Mercury, in arc rectifiers, is chosen for cathode because
(a) its ionization potential is relatively low
(b) its atomic weight is quite high
(c) its boiling point and specific heat are low
(d) it remains in liquid state at ordi¬nary temperature
(e) all of the above

Answer: e

20. The ionization potential of mercury is approximately
(a) 5.4 V
(b) 8.4 V
(c) 10.4 V
(d) 16.4 V

Answer: c

21. The potential drop in the arc, in a mercury arc rectifier, varies
(a) 0.05 V to 0.2 V per cm length of the arc
(b) 0.5 V to 1.5 V per cm length of the arc
(c) 2 V to 3.5 V per cm length of the arc
(d) none of the above

Answer: d

22. The voltage drop between the anode and cathode, of a mercury arc rectifier comprises of the following
(a) anode drop and cathode drop
(b) anode drop and arc drop
(c) cathode drop and arc drop
(d) anode drop, cathode drop and arc drop

Answer: d

23. Glass rectifiers are usually made into units capable of D.C. output (maximum continuous rating) of
(a) 100 A at 100 V
(b) 200 A at 200 V
(c) 300 A at 300 V
(d) 400 A at 400 V
(e) 500 A at 500 V

Answer: e

24. The voltage drop at anode, in a mercury arc rectifier is due to
(a) self restoring property of mercury
(b) high ionization potential
(c) energy spent in overcoming the electrostatic field
(d) high temperature inside the rectifier

Answer: c

25. The internal efficiency of a mercury arc rectifier depends on
(a) voltage only
(b) current only
(c) voltage and current
(d) r.m.s. value of current
(e) none of the above

Answer: a

26. If cathode and anode connections in a mercury arc rectifier are inter changed
(a) the rectifier will not operate
(b) internal losses will be reduced
(c) both ion and electron streams will move in the same direction
(d) the rectifier will operate at reduced efficiency

Answer: a

27. The cathdde voltage drop, in a mercury arc rectifier, is due to
(a) expenditure of energy in ionization
(b) surface resistance
(c) expenditure of energy in overcoming the electrostatic field
(d) expenditure of energy in liberating electrons from the mercury

Answer: d

28. To produce cathode spot in a mercury arc rectifier
(a) anode is heated
(b) tube is evacuated
(c) an auxiliary electrode is used
(d) low mercury vapour pressures are used

Answer: c

29. The advantage of mercury arc rectifier is that
(a) it is light in weight and occupies small floor space
(b) it has high efficiency
(c) it has high overload capacity
(d) it is comparatively noiseless
(e) all of the above

Answer: e

30. In a mercury pool rectifier, the voltage drop across its electrodes
(a) is directly proportional to load
(b) is inversely proportional to load
(c) varies exponentially with the load current
(d) is almost independent of load current

Answer: d

RECTIFIERS & CONVERTERS Multiple Choice Questions and Answers

31. In a three-phase mercury arc rectifiers each anode conducts for
(a) one-third of a cycle
(b) one-fourth of a cycle
(c) one-half a cycle
(d) two-third of a cycle

Answer: a

32. In a mercury arc rectifier characteristic blue luminosity is due to
(a) colour of mercury
(b) ionization
(c) high temperature
(d) electron streams

Answer: b

33. Which of the following mercury arc rectifier will deliver least undulating current?
(a) Six-phase
(b) Three-phase
(c) Two-phase
(d) Single-phase

Answer: a

34. In a glass bulb mercury arc rectifier the maximum current rating is restricted to
(a) 2000 A
(b) 1500 A
(c) 1000 A
(d) 500 A

Answer: d

35. In a mercury arc rectifier______ flow from anode to cathode
(a) ions
(b) electrons
(c) ions and electrons
(d) any of the above

Answer: a

36. When a rectifier is loaded which of the following voltage drops take place ?
(a) Voltage drop in transformer reactance
(6) Voltage drop in resistance of transformer and smoothing chokes
(c) Arc voltage drop
(d) All of the above

Answer: d

37. On which of the following factors the number of phases for which a rectifier should be designed depend ?
(a) The voltage regulation of the rec¬tifier should be low
(b) In the output circuit there should be no harmonics
(c) The power factor of the system should be high
(d) The rectifier supply transformer should be utilized to the best ad-vantage
(e) all of the above

Answer: e

38. A mercury arc rectifier possesses ________ regulation characteristics
(a) straight line
(b) curved line
(c) exponential
(d) none of the above

Answer: d

39. It is the_______of the transformer on which the magnitude of angle of overlap depends.
(a) resistance
(b) capacitance
(c) leakage reactance
(d) any of the above

Answer: c

41. In a grid control of mercury arc rectifiers when the grid is made positive relative to cathode, then it the electrons on their may to anode.
(a) accelerates
(b) decelerates
(c) any of the above
(d) none of the above

Answer: a

42. In mercury arc rectifiers having grid, the arc can be struck between anode and cathode only when the grid attains a certain potential, this potential being known as
(a) maximum grid voltage
(b) critical grid voltage
(c) any of the above
(d) none of the above

Answer: b

43. In phase-shift control method the control is carried out by varying the of grid voltage.
(a) magnitude
(b) polarity
(c) phase
(d) any of the above
(e) none of the above

Answer: c

44. In a phase-shift control method, the phase shift between anode and grid voltages can be achieved by means of
(a) shunt motor
(6) synchronous motor
(c) induction regulator
(d) synchronous generator

Answer: c

45. The metal rectifiers are preferred to valve rectifiers due to which of the following advantages ?
(a) They are mechanically strong
(b) They do not require any voltage for filament heating
(c) Both (a) and (b)
(d) None of the above

Answer: c

46. Which of the following statement is incorrect ?
(a) Copper oxide rectifier is a linear device
(b) Copper oxide rectifier is not a perfect rectifier
(c) Copper oxide rectifier has a low efficiency
(d) Copper oxide rectifier finds use in control circuits
(e) Copper oxide rectifier is not stable during early life

Answer: a

47. The efficiency of the copper oxide rectifier seldom exceeds
(a) 90 to 95%
(b) 85 to 90%
(c) 80 to 85%
(d) 65 to 75%

Answer: d

48. Copper oxide rectifier is usually designed not to operate above
(a) 10°C
(b) 20°C
(c) 30°C
(d) 45°C

Answer: d

49. Selenium rectifier can be operated at temperatures as high as
(a) 25°C
(b) 40°C
(c) 60°C
(d) 75°C

Answer: d

50. In selenium rectifiers efficiencies ranging from ______ to ______ percent are attainable
(a) 25, 35
(b) 40, 50
(c) 60, 70
(d) 75, 85

Answer: d

51. Ageing of a selenium rectifier may change the output voltage by
(a) 5 to 10 per cent
(b) 15 to 20 per cent
(c) 25 to 30 per cent
(d) none of the above

Answer: a

52. The applications of selenium rectifiers are usually limited to potential of
(a) 10 V
(b) 30 V
(c) 60 V
(d) 100 V
(e) 200 V

Answer: d

53. Which of the following rectifiers have been used extensively in supplying direct current for electroplating ?
(a) Copper oxide rectifiers
(b) Selenium rectifiers
(c) Mercury arc rectifiers
(d) Mechanical rectifiers
(e) None of the above

Answer: b

54. A commutating rectifier consists of commutator driven by
(a) an induction motor
(b) a synchronous motor
(c) a D.C. series motor
(d) a D.C. shunt motor

Answer: b

55. Which of the following rectifiers are primarily used for charging of low voltage batteries from AC. supply ?
(a) Mechanical rectifiers
(b) Copper oxide rectifiers
(c) Selenium rectifiers
(d) Electrolytic rectifiers
(e) Mercury arc rectifiers

Answer: d

56. The efficiency of an electrolytic rectifier is nearly
(a) 80%
(b) 70%
(c) 60%
(d) 40%

Answer: c

57. Which of the following is the loss within the mercury arc rectifier chamber ?
(a) Voltage drop in arc
(6) Voltage drop at the anode
(c) Voltage drop at the cathode
(d) All of the above

Answer: d

58. The metal rectifiers, as compared to mercury arc rectifiers
(a) operate on low temperatures
(b) can operate on high voltages
(c) can operate on heavy loads
(d) give poor regulation
(e) none of the above

Answer: a

59. In a mercury arc rectifier, the anode is usually made of
(a) copper
(b) aluminium
(c) silver
(d) graphite
(e) tungsten

Answer: d

60. The ignited or auxiliary anode in mercury arc rectifier is made of
(a) graphite
(b) boron carbide
(c) aluminium
(d) copper

Answer: b

[PDF Notes] The effects of inflation on different groups of society are as follows

Inflation results in redistribution of income and wealth because the prices of all the factors of production do not increase in the same proportion.

Generally, the flexible income groups, such as businessmen, traders, merchants, speculators gain during inflation due to wind-fall profits that arise because prices rise faster than the cost of production.

On the other hand, the fixed income groups, such as, workers, salaried persons, teachers, pensioners, interest and rent earners, are always the losers during inflation because their incomes do not increase as fast as the prices.

Inflation is unjust because it puts economic burden on those sections of the society who are least able to bear it. The effects of inflation on different groups of society are as follows:

1. Debtors and Creditors:

During inflation, the debtors are the gainers and the creditors are the losers. The debtors stand to gain because they had borrowed when the chasing power of money was highland now return the loans when the purchasing power of money is low due to inflation.

The creditors, on the other hand, stand to lose because they get back less in terms of goods and services than what they had lent.

2. Wage and Salary Earners:

Wage and salary earners usually suffer during inflation because (a) wages and salaries do not rise in the same proportion in which the prices or the cost of living rises and (b) there is a lag between a rise in the price level and a rise in wage and salary.

Among workers, those who have formed trade unions, stand to lose less than those who are unorganized.

3. Fixed Income Groups:

The fixed-income groups are the worst sufferers during inflation. Persons who live on past saving, pensioners, interest and rent earners suffer during periods of rising prices because their incomes remain fixed.

4. Business Community:

The business community, i.e., the producers, traders, entrepreneurs, speculators, etc., stand to gain during inflation, (a) They earn wind-fall profits because prices rise at a faster rate than the cost of production (b) They gain because the prices of their inventories go up, thus increasing their profits, (c) They also gain because they are normally borrowers of money for business purposes.

5. Investors:

The effect of inflation on investors depends on in which asset the money is invested. If the investors invest their money in equities, they are gainers because of the rise in profit. If the investors invest their money in debentures and fixed income bearing securities bonds, etc, they are the loser because income remains fixed,

6. Farmers:

Farmers generally gain during inflation because the prices of the farm products increase faster than the cost of production, thus leading to higher profits during inflation.

Thus inflation redistributes income and wealth in such a way as to harm the interests of the consumers, creditors, small investors, labourers, middle class and fixed income groups and to favour the businessmen, traders, debtors, farmers etc.

Inflation, is society unjust because it makes the rich richer and the poor poorer; it transfers wealth from those who have less of it to those who have already too much of it.

300+ TOP Synchronous Motors MCQ Questions and Answers

Synchronous Motors Questions :-

1. Synchronous motors are generally not self-starting because
A. the direction of rotation is not fixed
B. the direction of instantaneous torque reverses after half cycle
C. startes cannot be used on these machines
D. starting winding is not provided on the machines
Answer: B

2. In case one phase of a three-phase synchronous motor is short-circuited the motor will
A. not start
B. run at 2/3 of synchronous speed
C. run with excessive vibrations
D. take less than the rated load
Answer: A

3. A pony motor is basically a
A. small induction motor
B. D.C. series motor
C. D.C. shunt motor
D. double winding A.C./D.C. motor
Answer: A

4. A synchronous motor can develop synchronous torque
A. when under loaded
B. while over-excited
C. only at synchronous speed
D. below or above synchronous speed
Answer: C

5. A synchronous motor can be started by
A. pony motor
B. D.C. compound motor
C. providing damper winding
D. any of the above
Answer: D

6. A three-phase synchronous motor will have
A. no slip-rings
B. one slip-ring
C. two slip-rings
D. three slip-rings
Answer: C

7. Under which of the following conditions hunting of synchronous motor is likely to occur ?
A. Periodic variation of load
B. Over-excitation
C. Over-loading for long periods
D. Small and constant load
Answer: A

8. When the excitation of an unloaded salient pole synchronous motor suddenly gets disconnected
A. the motor stops
B. it runs as a reluctance motor at the same speed
C. it runs as a reluctance motor at a lower speed
D. none of the above
Answer: A

9. When V is the applied voltage, then the breakdown torque of a synchronous motor varies as
A. V
B. V312
C. V2
D. 1/V
Answer: A

10. The power developed by a synchronous motor will be maximum when the load angle is
A. zero
B. 45°
C. 90°
D. 120°
Answer: C

11. A synchronous motor can be used as a synchronous capacitor when it is
A. under-loaded
B. over-loaded
C. under-excited
D. over-excited
Answer: D

12. A synchronous motor is running on a load with normal excitation. Now if the load on the motor is increased
A. power factor as well as armature current will decrease
B. power factor as well as armature current will increase
C. power factor will increase but armature current will decrease
D. power factor will decrease and armature current will increase
Answer: D

13. Mostly, synchronous motors are of
A. alternator type machines
(6) induction type machines
C. salient pole type machines
D. smooth cylindrical type machines
Answer: C

14. The synchronous motor is not inherently self-starting because
A. the force required to accelerate the rotor to the synchronous speed in an instant is absent
B. the starting device to accelerate the rotor to near synchronous speed is absent
C. a rotating magnetic field does not have enough poles
D. the rotating magnetic field is produced by only 50 Hz frequency currents
Answer: A

15. As the load is applied to a synchronous motor, the motor takes more armature current because
A. the increased load has to take more current
B. the rotor by shifting its phase backward causes motor to take more current
C. the back e.m.f. decreases causing an increase in motor current
D. the rotor strengthens the rotating field casuing more motor current
Answer: B

16. Synchronous motor always runs at
A. the synchronous speed
B. less than synchronous speed
C. more than synchronous speed
D. none of the above
Answer: A

17. An over-excited synchronous motor takes
A. leading current
B. lagging current
C. both A. and B.
D. none of the above
Answer: A

18. The working of a synchronous motor is similar to
A. gear train arrangement
B. transmission of mechancial power by shaft
C. distribution transformer
D. turbine
E. none of the above
Answer: B

19. The minimum armature current of the synchronous motor corresponds to operation at
A. zero power factor leading
B. unity power factor
C. 0.707 power factor lagging
D. 0.707 power factor leading
Answer: B

20. In a synchronous motor, the magnitude of stator back e.m.f. £& depends on
A. d.c. excitation only
B. speed of the motor
C. load on the motor
D. both the speed and rotor flux
Answer: A

21. If load (or torque) angle of a 4-pole synchronous motor is 6° electrical, its value in mechanical degrees is
A. 2
B. 3
C. 4
D. 6
Answer: B

22. For V-curves for a synchronous motor the graph is drawn between
A. field current and armature current
B. terminal voltage and load factor
C. power factor and field current
D. armature current and power factor
Answer: A

23. The back e.m.f. of a synchronous motor depends on
A. speed
B. load
C. load angle
D. all of the above
Answer: C

24. A synchronous motor can operate at
A. lagging power factor only
(6) leading power factor only
C. unity power factor only
D. lagging, leading and unity power factors
Answer: D

25. In a synchronous motor which loss varies with load ?
A. Windage loss
B. Bearing friction loss
C. Copper loss
D. Core loss
Answer: C

26. A synchronous motor can be made self starting by providing
A. damper winding on rotor poles
B. damper winding on stator
C. damper winding on stator as well as rotor poles
D. none of the above
Answer: A

27. The oscillations in a synchronous motor can be damped out by
A. maintaining constant excitation
B. running the motor on leading power factors
C. providing damper bars in the rotor pole faces
D. oscillations cannot be damped
Answer: C

28. The shaft of synchronous motor is made of
A. mild steel
B. chrome steel
C. alnico
D. stainless steel
Answer: A

29. When the field of a synchronous motor is under-excited, the power factor will be
A. leading
B. lagging
C. unity
D. zero
Answer: B

30. The speed regulation of a synchronous motor is always
A. 1%
B. 0.5%
C. positive
D. zero
Answer: D

31. The percentage slip in case of a synchronous motor is
A. 1%
B. 100%
C. 0.5%
D. zero
Answer: D

32. The operating speed of a synchronous motor can be changed to new fixed value by
A. changing the load
B. changing the supply voltage
C. changing frequency
D. using brakes
Answer: C

33. A synchronous motor will always stop when
A. supply voltage fluctuates
B. load in motor varies
C. excitation winding gets disconnected
D. supply voltage frequency changes9885859805
Answer: C

34. riunting in a synchronous motor takes place
A. when supply voltage fluctuates
B. when load varies
C. when power factor is unity
D. motor is under loaded
Answer: B

35. When load on an over-excited or under excited synchronous*motor is increased, rate of change of its armature current as compared with that of power factor is
A. more
B. less
C. equal
D. twice
Answer: B

36. The rotor copper losses, in a synchronous motor, are met by
A. d.c. source
B. armature input
C. motor input
D. supply lines
Answer: A

37. The maximum power developed in a synchronous motor occurs at a coupling angle of
A. 30°
B. 60°
C. 90°
D. 180°
Answer: C

38. When the stator windings are connected in such a fashion that the number of poles are made half, the speed of the rotor of a synchronous motor
A. remains same as the original value
B. decreases to half the original value
C. tends to becomes zero
D. increases to two times the original value
Answer: D

39. In which of the following motors the stator and rotor magnetic field rotate at the same speed ?
A. Universal motor
B. Synchronous motor
C. Induction motor
D. Reluctance motor
Answer: B

40. Synchronsizingpower of a synchronous machine is
A. direcly proportional to the synchronous reactance
(6) inversely proportional to the synchronous reactance
A. equal to the synchronous reactance
D. none of the above
Answer: B

41. Synchronous motors are
A. not-self starting
B. self-starting
C. essentially self-starting
D. none of the above
Answer: A

42. The standard full-load power factor ratings for synchronous motors are
A. zero or 0.8 leading
B. unity or 0.8 lagging
C. unity or 0.8 leading
D. unity or zero
Answer: C

43. A synchronous motor running with normal excitation adjusts to load increases essentially by increase in
A. back e.m.f.
B. armature current
C. power factor
D. torque angle
Answer: B

44. A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because
A. synchronous motor has no slip
B. stator supply is not required to produce magnetic field
C. mechanical load on the rotor remains constant
D. synchronous motor has large airgap
Answer: B

45. A synchronous motor working at leading power factor can be used as
A. voltage booster
B. phase advancer
C. noise generator
D. mechanical synchronizer
Answer: B

46. Slip rings are usually made of
A. carbon or graphite
B. brass or steel
C. silver or gold
D. copper or aluminium
Answer: B

47. An over excited synchronous motor is used for
A. fluctuating loads
B. variable speed loads
C. low torque loads
D. power factor corrections
Answer: D

48. When the voltage applied to a synchronous motor is increased, which of the following will reduce ?
A. Stator flux
B. Pull in torque
C. Both A. and B.
D. None of the above
Answer: D

51. The efficiency of a properly designed synchronous motor will usually fall in range
A. 60 to 70%
(6) 75 to 80%
C. 85 to 95%
D. 99 to 99.5%
Answer: C

52. To limit the operating temperature an electrical machine should have proper
A. voltage rating
B. current rating
C. power factor
D. speed
Answer: B

53. Slip-rings in a synchronous motor carry
A. direct current
B. alternating current
C. no current
D. all of the above
Answer: A

54. A synchronous machine with large air gap has
A. a higher value of stability limit
(6) a small value of inherent regulation
C. a higher synchronizing power which makes the machine less sensitive to load variations
D. all of the above
Answer: D

55. The armature current of the synchronous motor has higher values for
A. high excitation only
B. low excitation only
C. both A. and B.
D. none of the above
Answer: C

56. In a synchronous motor running with fixed excitation, when the load is increased three times, its torque angle becomes approximately
A. one-third
B. twice
C. thrice
D. six times
E. nine times
Answer: C

57. The angle between the rotating stator flux and rotor poles is called _____ angle.
A. torque
B. obtuse
C. synchronizing
D. power factor
Answer: A

58. Which of the following methods is used to start a synchronous motor ?
A. Damper winding
B. Star-delta starter
C. Damper winding in conjunction with star-delta starter
D. Resistance starter in the armature circuit
Answer: C

59. When the rotor speed, in a synchronous machine, becomes more than the synchronous speed during hunting, the damper bars develop
A. inductor motor torque
B. induction generator torque
C. synchronous motor torque
D. d.c. motor toque
E. none of the above
Answer: B

60. An important advantage of a synchronous motor over wound round induction motor is that
A. its power factor may be varied at will
B. its speed is independent of supply frequency
C. its speed may be controlled more easily
D. none of the above
Answer: A

61. The mechanical displacement of the rotor with respect to the stator, in polyphase multipolar synchronous motors running at full load, is of the order of
A. zero degree
B. two degrees
C. five degrees
D. ten degrees
Answer: C

62. Power factor of a synchronous motor is unity when
A. the armature current is maximum
B. the armature current is minimum
C. the armature current is zero
D. none of the above
Answer: B

63. Change of D.C. excitation of a synchronous motor changes
A. applied voltage of the motor
B. motor speed
C. power factor of power drawn by the motor
D. any of the above
E. all of the above
Answer: C

64. While starting a synchronous motor by induction motor action, field winding is usually
A. connected to D.C. supply
B. short-circuited by low resistance
C. kept open-circuited
D. none of the above
Answer: B

65. Which of the following motors will be used in electric clocks ?
A. D.C. shunt motor
B. D.C. series motor
C. A.C. induction motor
D. A.C. synchronous motor
Answer: D

SYNCHRONOUS MOTORS Multiple Choice Questions and Answers

66. If in a synchronous motor, driving mechanical load and drawing current at lagging power factor from constant voltage supply, its field excitation is increased, then its power factor
A. become more
B. become less
C. remain constant
D. none of the above
Answer: B

67. A synchronous motor installed at the receiving end substation operates with such an excitation that it takes power at lagging power factor. Now if the applied voltage of the synchronous motor goes down, the power factor of the synchronous motor will
A. remain same
B. go down
C. improve
D. none of the above
Answer: C

68. While starting a salient pole synchronous motor by induction motor action and connecting field discharge resistance across field, starting and accelerting torque is produced by
A. induction motor torque in field winding
B. induction motor torque in damper winding
C. eddy current and hysteresis torque in pole faces
D. reHetance motor torque due to saliency of the rotor
E. all of the above methods
Answer: E

69. Armature of a synchronous machine is
A. of reducing number of slip rings on the rotor
B. armature is associated with large power as compared to the field circuits
C. of difficulty of providing high voltage insulation on rotor
D. all of the above reasons
Answer: D

70. If excitation of a synchronous motor running with a constant load is decreased from its normal value, ignoring effects of armature reaction, it leads to
A. increase in both armature current and power factor angle
B. increase in back e.m.f. but decrease in armature current
C. increase in both armature current and power factor which is lagging
D. increase in torque angle but decrease in back e.m.f.
Answer: A

71. When a 3-phase synchronous generator is supplying a zero power factor lagging load, the armature field affects the main field in the following way
A. augments it directly
B. directly opposes it
C. cross-magnetises it
D. none of the above
Answer: B

72. Stability of a synchronous machine
A. decreases with increase in its excitation
B. increases with increase in its excitation
C. remains unaffected with increase in excitation
D. any of the above
Answer: B

73. The power factor of a synchronous motor is better than that of induction motor because
A. stator supply is relieved of responsibility of producing magnetic field
B. mechanical load on the motor can be adjusted
C. synchronous motor runs at synchronous speed
D. synchronous motor has large air gap
Answer: A

74. If in a synchronous motor, driving a given mechanical load and drawing current at a leading power factor from constant voltage supply its field excitation is increased, its power factor
A. will become more
B. will become less
C. will remain unchanged
D. none of the above.
Answer: B

75. A synchronous motor is running with normal excitation. When the load is increased, the armature current drawn by it increases because
A. speed of the motor is reduced
B. power factor is decreased
C. Eb (back e.m.f.) becomes less than V (applied voltage)
D. Er (net resultant voltage) in armature is increased
E. none of the above
Answer: D

76. If one-phase of a 3-phase synchronous motor is short-circuited, motor
A. will refuse to start
B. will overheat in spots
C. will not come upto speed
D. will fail to pull into step
Answer: A

77. If the field circuit of an unloaded salientpole synchronous motor gets suddenly open-circuited, then
A. it runs at a slower speed
B. the motor stops
C. it continues to run at the same speed
D. it runs at a very high speed
Answer: B

78. In which of the following motors the stator and rotor fields rotate simultaneously ?
A. D.C. motor
B. Reluctance motor
C. Universal motor
D. Synchronous motor
E. Induction motor
Answer: D

79. The speed of a synchronous motor
A. increases as the load increases
B. decreases as the load decreases
C. always remains constant
D. none of the above
Answer: C

80. A rotory converter can also be run as a
A. d.c. shunt motor
B. d.c. series motor
C. d.c. compound motor
D. induction motor
E. synchronous motor
Answer: E

81. The maximum speed variation in a 3-phase synchronous motor is
A. 10 per cent
B. 6 per cent
C. 4 per cent
D. 2. per cent
E. zero
Answer: E

82. Which of the following resistances can be measured by conducting insulation resistance test on a synchronous motor ?
A. Phase to phase winding resistance
B. Stator winding to earthed frame
C. Rotor winding to earthed shaft
D. All of the above
Answer: D

83. Due to which of the following reasons a synchronous motor fails to pull into synchronism after applying D.C. field current ?
A. High field current
B. Low short circuit ratio
C. High core losses
D. Low field current
Answer: D

84. In a synchronous motor, the maximum power developed depends on all of the following except
A. rotor excitation
B. maximum value of coupling angle
C. direction of rotation
D. supply voltage
Answer: C

85. In a 3-phase synchronous motor, the negative phase sequence exists when the motor is
A. supplied with unbalanced voltage
B. under-loaded
C. over-loaded
D. none of the above
Answer: A

86. In a synchronous motor, damper windings are provided on
A. stator frame
B. rotor shaft
C. pole faces
D. none of the above
Answer: C

87. The induced e.m.f. in a synchronous motor working on leading power factor will be
A. more than the supply voltage
B. less than the supply voltage
C. equal to the supply voltage
Answer: A

88. The effect of increasing the load on a synchronous motor running with normal excitation is to
A. decrease both armature current and power factor
(6) decrease armature current but increase power factor
C. increase armature current but decrease power factor
D. increase both its armature current and power factor
Answer: C

89. The net armature voltage of a synchronous motor is equal to the
A. vector sum of Eb and V
B. arithmetic sum of Eb and V
C. arithmetic difference of Eb and V
D. vector difference of Eh and V
Answer: D

90. The ratio of starting torque to running torque in a synchronous motor is
A. zero
B. one
C. two
D. infinity
Answer: A

91. In a synchronous motor, the magnitude of stator back e.m.f. Eb depends on
A. load on the motor
B. d.c. excitation only
C. both the speed and rotor flux
D. none of the above
Answer: B

92. A 3-phase synchronous motor is running clockwise. If the direction of its field current is reversed
A. the motor will stop
B. the motor continue to run in the same direction
C. the winding of the motor will burn
D. the motor will run in the reverse direction
E. none of the above
Answer: B

93. The magnitude of field flux in a 3-phase synchronous motor
A. remains constant at all loads
B. varies with speed
C. varies with the load
D. varies with power factor
Answer: A

94. The torque angle, in a synchronous motor, is the angle between
A. the supply voltage and the back e.m.f.
B. magnetising current and back e.m.f.
C. the rotating stator flux and rotor poles
D. none of the above
Answer: C

95. Hunting in a synchronous motor cannot be due to
A. windage friction
B. variable load
C. variable frequency
D. variable supply voltage
Answer: A

96. By which of the following methods the constant speed of a synchronous motor can be changed to new fixed value ?
A. By changing the supply frequency
B. By interchanging any two phases
C. By changing the applied voltage
D. By changing the load.
Answer: A

97. In a synchronous motor, V-curves represent relation between
A. armature current and field current
B. power factor and speed
C. field current and speed
D. field current and power factor
Answer: A

98. In a 3-phase, 4-pole, 50 Hz synchronous motor, the frequency, pole number and load torque all are halved. The motor speed will be
A. 3000 r.p.m.
B. 1500 r.p.m.
C. 750 r.p.m.
D. none of the above
Answer: B

99. A synchronous motor connected to infinite bus-bars has at constant full load, 100% excitation and unity power factor. On changing the excitation only, the armature current will have
A. no change of power factor
B. lagging power factor with over-excitation
C. leading power factor with under-excitation
D. leading power factor with over-excitation
Answer: D

100. Which of the following motors is non-self starting ?
A. D.C. series motor
B. synchronous motor
C. Squirrel cage induction motor
D. Wound round induction motor
Answer: B

101. In a synchronous motor it the back e.m.f. generated in the armature at noload is approximately equal to the applied voltage, then
A. the motor is said to be fully loaded
B. the torque generated is maximum
C. the excitation is said to be zero per cent
D. the excitation is said to be hundred per cent
Answer: D

102. In a synchronous motor, the damping winding is generally used to
A. prevent hunting and provide the starting torque
B. reduce the eddy currents
C. provide starting torque only
D. reduce noise level
E. none of the above
Answer: A

103. If the field of a synchronous motor is underexcited, the power factor will be
A. zero
B. unity
C. lagging
D. leading
Answer: C

104. The back e.m.f. in the stator of a synchronous motor depends on
A. number of poles
B. flux density
C. rotor speed
D. rotor excitation
E. none of the above
Answer: D

105. The maximum value of torque that a synchronous motor can develop without losing its synchronism, is known as
A. slip torque
B. pull-out torque
C. breaking torque
D. synchronising torque
Answer: D

106. In a synchronous motor, the armature current has large values for
A. high excitation only
B. low excitation only
C. both high and low excitation
D. none of the above
Answer: C

107. Which of the following losses, in a synchronous motor, does not vary with load?
A. Windage loss
B. Copper losses
C. Any of the above
D. None of the above
Answer: A

108. The size of a synchronous motor decreases with the increase in
A. flux density
B. horse power rating
C. speed
D. all of the above
Answer: A

109. Which of the following losses is not dissipated by the stator core surface in a synchronous motor ?
A. Eddy current losses in the conductors
B. Iron losses in the stator
C. Copper losses in the slot portion of the conductors
D. Windage losses
E. None of the above
Answer: D

110. The duration of sudden snort-circuit test on a synchronous motor is usually about
A. one hour
B. one minute
C. one second
D. none of the above
Answer: C

111. The maximum constant load torque under which a synchronous motor will pull into synchronism at rated rotor supply voltage and frequency is known as
A. pull-up torque
B. pull-in torque
C. pull-out torque
D. none of the above
Answer: B

112. A synchronous machine with low value of short-circuit ratio has
A. lower stability limit
(6) high stability limit
C. good speed regulation
D. good voltage regulation
E. none of the above
Answer: A

113. The construction of a synchronous motor resembles
A. a series motor
B. an induction motor
C. an alternator
D. a rotary converter
Answer: C

114. If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will
A. stop
B. run as induction motor
C. function as static condenser
D. burn with dense smoke
Answer: A

115. For power factor correction, synchronous motors operate at
A. no-load and greatly over-excited fields
B. no-load and under-excited fields
C. normal load with minimum excitation
D. normal load with zero excitation
Answer: A

116. The maximum torque which a synchronous motor will develop at rest for any angular position of the rotor, at rated stator supply voltage and frequency, is known as
A. locked-rotor torque
B. synchronous torque
C. pull up torque
D. reluctance torque
Answer: A

117. Exciters of synchronous machines are
A. d.c. shunt machines
B. d.c. series machines
C. d.c. compound machines
D. any of the above
Answer: A

118. The coupling angle or load angle of synchronous motor is defined as the angle between the
A. rotor and stator teeth
B. rotor and the stator poles of opposite polarity
C. rotor and the stator poles of the same polarity
D. none of the above
Answer: B

119. If the synchronous motor, properly synchronised to the supply is running on no load and is having negligible loss then
A. the stator current will be zero
B. the stator current will be very small
C. the stator current will be very high
D. the back e.m.f. will be more than the supply voltage
E. none of the above
Answer: A

120 The armature current of the synchronous motor
A. has large values for low excitation i niy
B. has large values for high excitation only
C. has large values for low and high excitation
D. any of the above
Answer: C

121. The maximum power developed in a synchronous motor will depend on
A. the rotor excitation only
B. the supply voltage only
C. the rotor excitation and supply volt-age both
D. the rotor excitation, supply voltage and maximum value of coupling angle (90°)
E. none of the above
Answer: D

122. A synchronous motor which works on a leading power factor and does not drive a mechanical load is called as
A. static condenser
B. condenser
C. synchronous condenser
D. none of the above
Answer: C

129. A synchronous motor develops maximum power when load angle is
A. 45°
B. 60°
C. 90°
D. 120°
Answer: C

130. In a synchronous motor, the breakdown torque is
A. directly proportional to applied voltage
B. directly proportional to the square of the applied voltage
C. inversely proportional to applied voltage
D. none of the above
Answer: A

[PDF Notes] Here are your brief notes on Monetary Policy of Inflation

Monetary policy is adopted, by the monetary authority or the central bank of a country to influence the supply of money and credit by changing interest rate structure and availability of credit. Various monetary measures to control inflation are explained below:

1. Increasing Bank Rate:

Bank rate is the rate at which the central bank lends money to the commercial banks. An increase in the bank rate leads to an increase in the interest rate charged by commercial banks which, in turn, discourages borrowing by businessmen and consumers. This will reduce money supply with public and thus control the inflationary pressure.

2. Sale of Government Securities:

By selling government securities in the open market, the central bank directly reduces the cash reserves of the commercial banks because the central bank must be paid from these cash reserves.

The fall in the cash reserves compels the banks to reduce their lending activities. This will reduce the money supply and hence the inflationary pressures in the economy.

3. Higher Reserve Ratio:

Another monetary measure to check inflation is to increase the minimum reserve ratio. An increase in the minimum reserve ratio means that the member banks are required to keep larger reserves with the central bank. This reduces the deposits of the banks and thus limits their power to create credit. Restrictions on credit expansion will control inflation.

4. Selective Credit Control:

The purpose of selective credit control measures is to influence specific type of credit while leaving other types of credit unaffected.

Such selective measures are particularly important for developing economies in which, on the one hand, there is an increasing need for credit expansion for growth purposes, and, on the other hand, there is also need for checking inflationary tendencies.

In such a situation, selective credit control measures can direct the flow of credit from unproductive and inflation-prone sectors towards the productive and growth oriented sectors. The main selective credit control measures to control inflation are:

(i) Consumer Credit Control:

This method is adopted during inflation to curb excessive spending by consumers. In advanced countries, most of the durable consumer goods, such as, radio, T.V., Fridge, etc.; are purchased by the consumers on installment credit.

During inflation, loan facilities for installment buying are reduced to minimum to check consumption spending.

This is done by (a) raising the initial payment, (b) covering the large number of goods, and (c) reducing the length of the payment period.

(ii) Higher Margin Requirements:

Margin requirement is the difference between the market value of the security and its maximum loan value. A bank does not advance loan equal to the market value of the security, but less.

For example, it may lend Rs. 600 against the security worth Rs.1000; thus the margin requirement in this case is 40%. During inflation, the margin requirement can be raised to reduce the loan one can get on a security.