chapter three AC generator ( dynamo ) Flashcards

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1
Q

diff the linear velocity and relation and unit

A

it is the displacement in on second

Vel = DX \ Dt m \ sec

NOTE ; X ⇒ is the displacment or distance coverd

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2
Q

diff angular velocity and relation and unit and all rules you know

A

it is the angle coverd in one second

ŵ = seta \ t radian \ sec

NOTE ; 2= if seta = 2π = 360 . the time taken be called periodic time ( T )

ŵ = 2π \ T SINCE Freq = 1 \ T

ŵ = 2πF

ŵ = V \ r

NOTE ; r ⇒ length of arc of circle

wedth of the rectangle coil rotates = 2r

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3
Q

what is the function of the dynamo

A

it is the device to convert the mechanical energy int electric energy

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4
Q

what is the idea of the operation of the dynamo

A

it depends on the electromagnetic induction when the coil rotates in magnetic filed E.M.F will be indused

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5
Q

what is the construction of the dynamo and the uses

A
  1. the filed magnet : it may be a perment magnet or an electric magnet
  2. the armature : is is a wire loop rotates between the two poles of the magnet
  3. slip rings with brushes :
  • each of the two ends of the coil is connected to one of a pair of slip rings , rotates with the rotation of the loop in the magnetic filed
  • each one of the pair of slip rings touches one of two graphite brushes to conduct the induced current from the coil to the external circuit
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6
Q

the dirction of the indused current is reversed each …… turn so it called …………….

A
  1. ½
  2. alternation current

NOte alternating current بيغير اتجاهه دايما

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7
Q

prove the relation on electricromotive force indused in dynamo

A

draw in page 135

Eind of wire =B x L x V x SINseta

Eind of coil =2 x B x L x V x SINseta

Eind of dynamo =2 x B x L x ŵ x SINseta

since;A = L x 2r (width)

Eind of dynamo = A x B x ŵ x SINseta

for N of number of turns

Eind of dynamo = A x B x N x ŵ x SINseta

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8
Q

diff seta in the relation of the electro motive force in dynamo

A

it is the angle betweent the dirction of the velocity of the wire and the magnetic flux lines

OR

it is the angle between the normal to the coils plane and the magnetic flux lines

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9
Q

when the indused E.M.F reaches maximum

A

seta = 90

when the coils plane parallel to the mahnetic flux lines

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10
Q

the indused E.M.F become zero

A

seta = zero

coils plane perependculer to the magnetic flux lines

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11
Q

what happen during each complete revolution of the dynamo coil on graph and draw it

A

sin curve in page 136

the indiced E.M.F changes from zero to maximum value to zero to maximum value in opposite direction to zero forming on complete vibration during each complete revolution of the dynamo coil

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12
Q

diff frequency of the AC and the relation and unit

A
  • it is the number of the complete vibrations of the AC in one seconed

OR

it isthe number of the revolutions of the dynamo coil in one second

  • F = number of complete revolution \ time
  • cycle \ sec OR HZ
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13
Q

what is the number of turns that AC reaches maximum value in one secound

what is the number of turns that AC current reaches zero in on secound

A

2F

2F+1

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14
Q
  • the maximum E.M.F is obtained at angle ……. when the coils plane is to the magnetic flux lines
  • Half the maximum E.M.F is obtained at angle ……. when the coils plane makes angle to the magnetic flux lines
  • the effective value is obtained at angle ……. when the coils plane makes angle to the magnetic flux lines
A
  1. 90
  2. parallel
  3. 30
  4. 60
  5. 45
  6. 45
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15
Q

if the E.M.F induced from the dynamo takes time (t) to reach half it maximum value from the starting ZERO position , SO it takes time ……. to reach maximum value while for periodic time or completer revolution ………

A
  1. 3t
  2. 12t
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16
Q

diff effective value of AC and relation

A

it id the value of the DC that generates the same power generated by the AC

Eeffective = Emax X sin45

Ieffective = ImaxXsin45

17
Q

what is the current rectification

A

it is conversion of the AC into DC by replacing the two metallic rings by rectifier called COMMUTATOR

18
Q

what is the commutrtor

A

it is the two X and Y of a hollow metalic cylinder are well insulated from each other

19
Q

what is uni-directional current dynamo

A

it is a device to produce uni-directional current of approximately constant value

20
Q

how turn dynamo from AC current int DC

A

by adding the commutator and uni-directional current dynamo

21
Q

how to obtain a uni-directional current of approximately constant value

A
  • A number of coils are used with equel angles between them and the commutator cylinderis divided into twice the number of the coils
  • eash pair of opposite parts of the commutator is connected to terminals of a coil
  • during rotation each two parts of the comutator touch the two brushes when the plane of their coil is parrallel to the lines of the magnetic flux lines to generate maximum induced E.M.F from this coil
22
Q

draw graph of the following

  1. direct current
  2. alternating current
  3. uni-directional current
    1. uni-directional current of approximately constant value
A

in page 140

23
Q
A