electromagnet 8.4
TRANSCRIPT
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FORM 5© COPYRIGHT BY SUPER EDUCATION GROUP (J
CHAPTER 8: Electr!"#$et8%& Tr"$'r!er
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CHAPTER 8: Electr!"#$et
8.4: Transformers
1. In Malaysia, our electricity for domestic supplied at a voltage of ……………… a.c.
2. However, most of home appliances at home use lower than or higher than 240.!. "ransformers are found in many devices such as ………………., …………………., …………………..
and etc.
4. "he main use of transformer is to convert ……………………. #$ oltage to ……………. one or vice%
versa.
# transformer is a device which step ups or steps down alternating current voltage
Operating principle of a transformer
&. 'ased on the electromagnetic induction, the a.c voltage is applied to the primary coil of a transformer,
an alternating current flow through the circuit.
(. )hen an alternating current flows in primary coil, and magnetic field is produced in the soft iron core.
*. Magnetic flu+ linage to secondary coil and will cut the magnetic fields lines.
-. "he secondary coil e+periences the rate of change of magnetic field and current is induced in secondary
coil. induced e.m.f /
. )hen the current in primary coil decreases, the magnetic field will collapse and again cut the secondary
coil.
10. #n e.mf acting in the opposite direction is induced in the secondary coil.
11. Hence, an alternating e.m.f of the same freuency is induced in the secondary coil.
12. "he output voltage is depends on the ratio of numer of turns of primary and secondary coils.
PREPARED BY JJ MREON P"#e *© COPYRIGHT BY SUPER EDUCATION GROUP (JOHOR JAYA)
240 V
mobilelaptopstelevision
small larger
Laminated soft-iron
OUTPUTINPUT
SecondaryPrimary coil
ymbol of
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CHAPTER 8: Electr!"#$et
Step-up and step-down transformers
1. "he relationship etween the voltages and the ratio of the turns in primary and secondary coils can e
If Ns is greater than Np, then Vs is ………………… than Vp. "he type of transformer is
………………………….
If Ns is less than Np, then Vs is ………………… than Vp. "he type of transformer is
………………………….
3or e+ample, if the turns ratio is 1&0, the output voltage is stepped up ……….. times.
PREPARED BY JJ MREON P"#e +© COPYRIGHT BY SUPER EDUCATION GROUP (JOHOR JAYA)
N,!-er t,r$' .$ /r.!"r0 c.l
N,!-er t,r$' .$ 'ec$1"r0=
Pr.!"r0 2lt"#e
Sec$1"r0
=Vs
Ns
Vp
Np
Np
Ns
Vp
Vs= OR
less
step-!p
step-do#n
tep-!ptep-do#n
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CHAPTER 8: Electr!"#$et
PREPARED BY JJ MREON P"#e 3© COPYRIGHT BY SUPER EDUCATION GROUP (JOHOR JAYA)
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CHAPTER 8: Electr!"#$et
Energy losses in a transformer
#s we now, an ideal transformer has ………….. effiency.
'ut in practice, the efficiency of a tranformer is …………….. 1005.
"he effiency of a transformer is e+pressed as follows
PREPARED BY JJ MREON P"#e &© COPYRIGHT BY SUPER EDUCATION GROUP (JOHOR JAYA)
Po#er !sed in
the secondary=Po#er s!pplied
to the primary
=
Vp
Vs=
Is
Ip
VpI
p
VsIs
C!/"r.$# 4.t te
tr"$'r!er e6,"t.$Is
Ip
Np
Ns=
$00%
less than
1005
1005
Pout
Pin
VsIs
VpIp
η = ×
= ×
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CHAPTER 8: Electr!"#$et
13. $omplete the tale elow
Type of losses Causes Way to reduce
Eddy current • current induced in the core due to
electromagnetic induction.
• $hanging of magnetic field induced
current in soft iron core
Eddy current produced and generate
heat
Use laminated core
higher resistance to reduce eddy
current
Heat loss • #s the numer of turn increases, the
resistance of conductor also increases.
Heat produced by electrical energy to
oppose the resistance
Use low resistance copper
/aluminium wires
Thick wire to reduce resistance
Hysterisis loss
/magnetism and
demagnetizatio
n of the core
• "he core is magneti6ed and
demagneti6ed alternately due to a.c
current in primary coil
Energy loss as heat
Use soft-iron core
t is able to be magnetized and
demagnetized easily
3lu+ leaage • 7eaage of magnetic flu+ in the
primary coil
!roper core design
wind the primary coil on the top of
the secondary coils
PREPARED BY JJ MREON P"#e 5© COPYRIGHT BY SUPER EDUCATION GROUP (JOHOR JAYA)
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CHAPTER 8: Electr!"#$et
PREPARED BY JJ MREON P"#e © COPYRIGHT BY SUPER EDUCATION GROUP (JOHOR JAYA)
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He"20 .$1,'tr0
.#t .$1,'tr0
1 kV
B,.l1.$#'
240 V
M0 ,'e
CHAPTER 8: Electr!"#$et
8.: !eneration and Transmission of Electricity
Sources of Energy
1. "he generation of electricity comes from many sources such as
"% H01r
-% G"'e'c% N,cle"r1% D.e'ele% C"l% B.!"''#% Sl"r% 9.$1
"ational !rid "etwor#
2. 8ational 9rid 8etwor is a networ of underground cales or …………… which connect all the power
stations and sustations for the whole country.!. "his networ starts at electrical power plant lie $henderoh 7ae :ower ;tation which is hydroelectric
power station, and end at our houses.
4. $omplete the diagram elow y showing the cales of transmission and suitale users.
&.
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132 kV
CHAPTER 8: Electr!"#$et
2
heat P I R=
*. "he power loss can reduce y
i. =educing the ……………………… of the cales
ii. =educing the current or ……………………. the voltage in the cale.
#dvantages of use national grid networ
1. easy to manage =egional control and switching centres enale power to
e sent where and when it is needed.
2. 7ess interruptions and continuously =egional control and switching centres allow some
stations and lines to e shut down for maintenance wor
without cutting off the supply to the consumers
!. =educing cost of generation High voltage transmission can reduce the power loss in
transmission cales. "he cost production is reduced.
4. uring periods of low
demand, some generators can e turned off.
$enewa%le energy
=enewale energy sources are continually replenished naturally means they are sustainale.
&. 9ive the e+ample of renewa%le energy
I% H01relectr.cII% Sl"rIII% 9.$1I% Geter!"l
% B.!"''I% 9"2eII% T.1"l
(. 9ive the e+ample of non-renewa%le energy
i. ……………………..
a& 'ilb& (asc& )oal
*. 9ive the enefits of using the renewale energy to our nation
PREPARED BY JJ MREON P"#e ;© COPYRIGHT BY SUPER EDUCATION GROUP (JOHOR JAYA)
I < c,rre$t =4' .$ te c"-le
R < re'.'t"$ce te c"-le
resistance
increasing
F''.l ,el ',c
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33 >
tr"$'!.''.$
CHAPTER 8: Electr!"#$et
a* +void depletion of fossil f!elsb* )leaner so!rces for little poll!tionc* +void harming ,ora and fa!nad* +void the disr!ption of ecological balance
PREPARED BY JJ MREON P"#e *?© COPYRIGHT BY SUPER EDUCATION GROUP (JOHOR JAYA)