Physics KSSM F5 Zen Notes by Cikgu Heery
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Heery’s Zen Notes
Physics KSSM F5
2021
Chapter 4:
Physics KSSM F5 Zen Notes by Cikgu Heery
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A. FORCE ON A CONDUCTOR WITH CURRENT/
DAYA KE ATAS KONDUKTOR PEMBAWA ARUS
1. We MUST know on how to determine the direction of force on the conductor by using Fleming’s Left Hand Rule
Kita WAJIB tahu cara menentukan arah daya ke atas konduktor dgn menggunakan Petua Tangan Kiri Fleming
QUESTION EXAMPLE – determine the direction of force on the conductor below /tentukan arah daya ke atas konduktor di bawah:
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2. We also MUST know how to draw the catapult field/ Kita juga WAJIB tahu melukis medan lastik:
QUESTION EXAMPLE – Draw catapult field & force direction/ lukiskan medan lastik & arah daya
ANSWER:
SPM QUESTION:
Here is a conductor with magnet. Determine the direction of force on it. Ini ialah konduktor dengan magnet. Tentukan arah daya ke atasnya
ANSWER: D
Use Right Hand Grip
Rule
Guna Petua
Genggaman Tangan Kanan
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3. Application – direct current motor/ Aplikasi – motor arus terus
a. How to increase the rotation speed of motor?/ Cara meningkatkan kelajuan putaran motor?
Increase current/ voltage or reduce resistance Tingkatkan arus/ voltan atau kurangkan rintangan
Use stronger magnet
Guna magnet lebih kuat
Increase the number of wire turns in coil
Tambahkan bilangan lilitan gegelung
b. Brushless motor & brushed motor/ Motor tanpa berus & motor berberus:
BRUSHLESS MOTOR
MOTOR TANPA BERBERUS
BRUSHED MOTOR
MOTOR BERBERUS
NO BFF – no brush, no friction, no fire
sparks
Tiada berus, tiada geseran, tiada percikan api
Got BFF – has brush, generate friction,
generate fire sparks
Ada berus, jana geseran, hasilkan percikan api
Magnet rotates, coil stationary
Magnet putar, gegelung pegun
Coil rotates, magnet stationary
Gegelung putar, magnet pegun
Use Fleming’s Left
Hand Rule to
determine the direction of rotation Guna Petua Tangan Kiri Fleming utk menentukan arah putaran
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B. ELECTROMAGNETIC INDUCTION/ ARUHAN
ELEKTROMAGNET
1. Describing the induction/ Huraian aruhan:
a. Move conductor across the magnetic field (relative motion happens) Gerakkan konduktor merentas medan magnet (gerakan relatif berlaku) b. We are changing or cutting the magnetic flux
Kita mengubah atau memotong fluks magnet
c. This will generate induction electromotive force (emf) Ini menjana daya gerak elaktrik (dge) aruhan
d. Induction EMF will generate induction current DGE aruhan menjana arus aruhan
2. Faraday Law/ Hukum Faraday:
“The higher the rate of cutting flux magnet, the higher the
magnitude of induction EMF”
“Makin tinggi kadar pemotongan fluks magnet, makin tinggi
magnitud dge aruhan
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3. To determine the direction of induction current, we use Fleming’s Right Hand
Rule
Utk menentukan arah arus aruhan, kita guna Petua Tangan Kanan Fleming
Faraday Law’s application – the faster we move wire, the higher the galvanometer reading!
Aplikasi Hukum Faraday – makin laju kita gerakkan dawai, makin besar bacaaan galvanometer!
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4. For solenoid, we use Lenz Law to determined the direction of induction current/ Utk solenoid, kita gunakan Hukum Lenz utk menentukan arah arus aruhan
When we insert magnet, solenoid will
have same pole with inserting magnet
Apabila kita masukkan magnet, solenoid akan mempunyai kutub sama dgn magnet yg masuk
When we pull out magnet, solenoid will
have different pole
Apabila kita tarik keluar magnet, solenoid akan mempunyai kutub berbeza
*Use Right Hand Grip Rule to determine the direction of current in solenoid/ Guna Petua Genggaman Tangan Kanan utk menentukan arah arus dlm solenoid
5. How to increase the galvanometer reading?/ Cara meningkatkan bacaan galvanometer?
Move magnet faster
Gerakkan magnet lebih pantas
Use stronger magnet
Guna magnet lebih kuat
Increase the number of wire turns in solenoid Tambahkan bilangan lilitan solenoid
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6. Application – direct current (dc) generator & alternating current (ac)
generator/
Aplikasi – penjana arus terus (at) & penjana arus ulang alik (au)
DC GENERATOR
PENJANA AT
AC GENERATOR
PENJANA AU
Work principle:
Move coil cut magnetic flux generate induction emf induction current Prinsip kerja:
Gerakkan gegelung potong fluks magnet jana dge aruhan jana arus aruhan
Has one carbon brush Ada satu berus karbon
Has two carbon brush Ada dua berus karbon Generate current in one direction
Jana arus satu hala
Generate current in alternating direction Jana arus yg gerak ulang alik
5. How to increase the induction current?/ Cara meningkatkan arus aruhan? Move coil faster
Gerakkan gegelung lebih pantas
Use stronger magnet
Guna magnet lebih kuat
Increase the number of wire turns in coil
Tambahkan bilangan lilitan gegelung
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C. TRANSFORMER
1. Simple transformer structure/ Struktur transformer ringkas:
Revision/ Ulangkaji:
- Function: change voltage / Fungsi: ubah voltan
- Use alternating current (ac) / Guna arus ulang-alik (au)
2. Transformer’s work principle/ Prinsip kerja transformer: a. AC power source generates ac current in primary coil Penjana kuasa au hasilkan arus au dalam gegelung primer
b. This will generate changing magnetic flux in soft iron core. SIC binds magnetic
flux from primary to secondary coil
Ini akan menjana fluks magnet yg berubah-ubah dalam teras besi lembut. TBL
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c. Changing magnetic flux will change the voltage in the secondary coil Fluks magnet yg berubah akan mengubah voltan dalam gegelung sekunder
3. Calculation/ Pengiraan:
a. Voltage calculation/ Pengiraan voltan:
Voltage in primary coil (pc) = Voltage in secondary coil (sc)
Number of wire turns in pc Number of wire turns in sc
V
p= V
sN
pN
sb. Transformer efficiency/ Kecekapan transformer:
Efficiency = Output power x 100%
Input power
= V
sI
sx 100%
V
pI
pc. For efficient transformer… / Untuk transformer unggul…
Input power = Output power
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QUESTION EXAMPLE:
a. Here is an example of transformer. Calculate the value of output voltage. Ini ialah contoh transformer. Kirakan nilai voltan output
Answer:
V
p= V
sN
pN
s240 = V
s100 250
V
s= 600V
b. This is an example of efficient transformer. Calculate the output current Ini ialah contoh transformer unggul. Kirakan arus output
Power input = power output
200W= I
sx V
s200W = I
sx 50V
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4. How to reduce energy loss in transformer?
Cara mengurangkan kehilangan tenaga dalam transformer
METHOD
WHY?
a. Use thicker wire Guna wayar lebih tebal
To reduce resistance
Utk mengurangkan rintangan b. Use laminated soft iron core
Guna teras besi lembut berlamina
To reduce eddy current
Utk mengurangkan arus pusar c.Use soft iron as core
Guna besi lembut sebagai teras
To reduce histerisis
Utk mengurangkan histerisis d.Wrap the secondary coil over primary coil
Lilitkan gegelung sekunder di atas gegelung primer
To prevent magnetic flux leakage Utk mencegah kebocoran fluks magnet
5. Use of eddy current in induction cooking/ Kegunaan arus pusar dalam dapur aruhan
a. AC power source generate high-frequency ac Punca kuasa au hasilkan au berfrekuensi tinggi b. This will generate changing magnetic flux Ini menjana fluks magnet yg berubah-ubah c. This produces eddy current in the frying pan Ini menghasilkan arus pusar dalam kuali
d. Heat in generated in the pan for cooking Haba dihasilkan dalam kuali utk memasak
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6. Transmission & distribution system of electrical energy/ Sistem penghantaran & pengagihan tenaga elektrik
a. Step-up transformer is used after the power station
Transformer injak naik digunakan selepas stesen janakuasa
b. This is to increase voltage so to send electricity at faraway places using
National Grid Network
Ini utk meningkatkan voltan utk menghantar elektrik ke tempat jauh melalui Rangkaian Grid Nasional
c. After that, step-down transformers are used. Kemudian transformer injak turun digunakan
d. This is to reduce voltage according to building requirement Ini utk mengurangkan voltan mengikut keperluan bangunan
