chapter three AC generator ( dynamo )

Question 1

diff the linear velocity and relation and unit

Answer 1

it is the displacement in on second

V_el = DX \ Dt m \ sec

NOTE ; X ⇒ is the displacment or distance coverd

Question 2

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

Answer 2

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

Question 3

what is the function of the dynamo

Answer 3

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

Question 4

what is the idea of the operation of the dynamo

Answer 4

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

Question 5

what is the construction of the dynamo and the uses

Answer 5

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

Question 6

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

Answer 6

1. ½
2. alternation current

NOte alternating current بيغير اتجاهه دايما

Question 7

prove the relation on electricromotive force indused in dynamo

Answer 7

draw in page 135

E_{ind of wire} =B x L x V x SINseta

E_{ind of coil} =2 x B x L x V x SINseta

E_{ind of dynamo} =2 x B x L x ŵ x SINseta

since;A = L x 2r (width)

E_{ind of dynamo} = A x B x ŵ x SINseta

for N of number of turns

E_{ind of dynamo} = A x B x N x ŵ x SINseta

Question 8

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

Answer 8

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

Question 9

when the indused E.M.F reaches maximum

Answer 9

seta = 90

when the coils plane parallel to the mahnetic flux lines

Question 10

the indused E.M.F become zero

Answer 10

seta = zero

coils plane perependculer to the magnetic flux lines

Question 11

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

Answer 11

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

Question 12

diff frequency of the AC and the relation and unit

Answer 12

• 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

Question 13

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

Answer 13

2F

2F+1

Question 14

• 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

Answer 14

1. 90
2. parallel
3. 30
4. 60
5. 45
6. 45

Question 15

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 ………

Answer 15

1. 3t
2. 12t

Question 16

diff effective value of AC and relation

Answer 16

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

E_effective = E_max X sin45

I_effective = I_maxXsin45

Question 17

what is the current rectification

Answer 17

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

Question 18

what is the commutrtor

Answer 18

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

Question 19

what is uni-directional current dynamo

Answer 19

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

Question 20

how turn dynamo from AC current int DC

Answer 20

by adding the commutator and uni-directional current dynamo

Question 21

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

Answer 21

• 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

Question 22

draw graph of the following

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

Answer 22

in page 140