Tema 2 : Menyiasat Daya dan Tenaga

Tenaga

Kegunaan Tenaga

1. Tenaga adalah keupayaan untuk melakukan kerja.

Sumber Tenaga

1.         Matahari →Sumber utama tenaga

                             →Membekalkan cahaya dan haba kepada kita.

                             →Tumbuhan memerlukan cahaya matahari untuk membuat makanan

        (Fotosintesis). Tenaga dipindahkan kepada manusia dan haiwan melalui

         memakannya.

2.         Makanan →Makanan mempunyai tenaga. Tenaga digunakan untuk menjalankan

         aktiviti seharian.

3.         Angin →Tenaga angin boleh ditukar kepada tenaga elektrik menggunakan turbin.

                       → Tenaga angin yang diguna secara langsung → kapal layar

                                                                                                                 Layang-layang

                                                                                                                 Mengepan air

                                                                                                                 Menghancurkan bijian

4.         Bahan api → Arang batu, petroleum, gas asli

5.         Bateri  → Tenaga yang disimpan dalam bateri boleh ditukar kepada tenaga elektrik.

Pelbagai bentuk tenaga

1.         Tenaga Kinetik → Objek yang bergerak mempunyai tenaga kinetic.

2.         Tenaga Haba → Menyebabkan objek menjadi panas

                                      → Sumber tenaga haba : Matahari, lilin yang terbakar, kayu yang

       sedang terbakar, lampu yang menyala.

3.         Tenaga Elektrik → Pengaliran cas-cas elektrik

                                        → Cas-cas elektrik yang bergerak melalui wayar ialah elektrik.

4.         Tenaga Bunyi  → Dihasilkan oleh getaran

                                      → Bunyi dipindah melalui udara, cecair dan pepejal.

                                           (Bunyi tidak dapat didengar tanpa bahan ini)

5.         Tenaga keupayaan → Tenaga yang tersimpan dalam objek yang bergantung

     kepada kedudukan dan keadaan objek.

→ Tenaga keupayaan boleh ditukar kepada bentuk lain.

6.         Tenaga Kimia  → Tenaga yang tersimpan dalam bahan.

                                      → Contoh : biojisim, petroleum, gas asli, propana dan makanan.

7.         Tenaga Cahaya → Sumber utama matahari dan juga objek yang mengeluarkan

           cahaya.

Perubahan Tenaga

Tenaga yang boleh diperbaharui dan tidak boleh diperbaharui

1.         Sumber tenaga yang boleh diperbaharui:

           

a)        Suria

b)        Angin

c)        Biojisim

d)        Air

2.         Sumber tenaga yang tidak boleh diperbaharui

           

a)                 Gas asli

b)                 Atom Nuklear

c)                 Petroleum

d)                 Arang

e)                 Arang batu

3.         Kelebihan tenaga yang boleh diperbaharui

a)     Boleh diganti setelah habis digunakan dalam masa yang singkat.

Cara Menjimatkan Tenaga

1.         Tutup suis alat elektrik apabila tidak digunakan.

2.         Menggunakan kenderaan awam atau berkongsi kenderaan.

3.         Mengganti mentol biasa dengan mentol jimat tenaga.

MAKING HYPOTHESES


DEFINITION

- Hypotheses are general statements about objects or events based on
explainable observation .

- Hypotheses are built based on inferences made on a certain investigation
or fair test .

- Hypotheses are relationship between two variables , the what to change
( manipulated ) variable and the what to observe or measure ( response )
variable .


STEPS IN ANSWERING


- Identify the what to change ( manipulated ) variable .

- Identify the what to observe / measure ( response ) variable .

- You must state what happen to the thing to measure/observe (whether increases or
decreases) if the thing to change is increased or decreased.

- Do not mention the what to keep the same ( constant ) variables in the
hypotheses .

- Every variables written in the hypothesis must have the ‘ parameter ’ .

- Hypotheses can be written in the reversible facts .

OBSERVATION AND MAKING INFERENCES

DEFINITION

Observation

Observation is a process to state or explain about an object or phenomenon
that happens . Observation uses the sense of sight , hearing , smell , taste and touch . If observation is made on more than one object or situation , we have
to make comparison . Without comparison , the observation will not be precise .

Inference

It is a process of making an early conclusion to explain an event or object using experiences . Past experiences are used as the main foundation in making
the early conclusion . Conclusions that are made might be true or false .


STEPS IN ANSWERING OBSERVATION AND INFERENCE

1. First carefully observe the objects or graphs .
2. Make any additional observation that are related to the surrounding objects
or graphs .
3. State explanations or reasons to why they happen .


GUIDE IN WRITING ANSWERS

There are 2 methods in writing the answers on making inference are as follows :

1. State the observation and give reasons to why it happens .
2. Give reasons on the events without prior observation .
3. If the questions is on comparison , the answer must show the comparison
by using words like more , while and comparison itself .

MISTAKES DONE

1. Students state observations without the reasons .
2. Students fail to give the additional observation because they are unable
to make the observation conscientiously .

Kemandirian Spesies	kebolehan mengekalkan spesiesnya supaya tdk pupus/habis mati
	haiwan	menjaga telur	buaya, ular
		menjaga anak	gajah, kerbau
		menyusukan anak	lembu,kuda, dolpin, kelawar
		telur berlendir	katak
		sembunyikan telur	lipas, siput, cicak
		tinggal berkumpulan	gajah
		masukkan anak dlm pouch	kanggaroo (dpt perlindungan, haba & menyusu)
		bertelur banyak	katak
	tumbuhan	utk elak persaingan sumber keperluan	air, cahaya matahari, nutrien, ruang
			yg dpt sumber keperluan hidup subur, yg tdk dpt akan terbantut pertumbuhan, layu atau mati
		ciri2	-daun berbulu (elak dimakan haiwan & kehilangan air berlebihan) -daun tebal & berlilin (elak kehilangan air berlebihan) -akar panjang (utk dptkan air & nutrien) -tumbuh tinggi (dptkan cahaya matahari) -memanjat pokok lain (dptkan cahaya matahari)
		penyebaran biji benih	air haiwan angin mekanisma letupan

ELECTRICITY

Sources of electricity

1.     Electricity is a form of energy.

2.     Many appliances in our home need electricity to work such as light, television, radios, irons, refrigerator and rice cookers.

3.     The electricity that we use everyday comes from different sources.

4.     There are various sources of electricity.

DRY CELL

1.     Small and light.

2.     Supplies slight electrical energy.

3.     Contains chemicals that react so that chemical energy is changed to electrical energy.

4.     Does not last long and is thrown away when the chemical substance inside is used up.

5.     Normally used for torches, toys, stereos, remote controls, alarm clocks, etc.

SOLAR CELL

1.     Absorbs solar energy and transforms it into electrical energy.

2.     Solar cells are used in some calculators and watches.

3.     Some water heaters also use solar energy.

ACCUMULATOR

1.     Consists of a few lead plates immersed in dilute sulphuric acid.

2.     Lead plates react with dilute sulphuric acid to produce electrical energy.

3.     Heavy.

4.     Supplies greater electrical energy compared to dry cell.

5.     Lasts longer and can be recharged.

6.     Normally used in motor vehicles.

DYNAMO

1.     Normally fixed  to bicycle wheel.

2.     Produces electrical energy from magnetic rotation.

3.     Normally used to light up bicycle lights.

HYDROELECTRICAL POWER

1.     Produces great electrical energy.

2.     It is like a big dynamo.

3.     The dynamo rotates using energy from fuels or a waterfall.

ELECTRIC  CIRCUIT

1.     An electrical current only flow through a complete circuit.

2.     A simple complete circuit is build by connecting a dry cell, wires and a bulb correctly.

3.     we can also build different electric circuits using dry cells, wires and a bulb.

4.     A bulb will not light up if the circuit is incomplete.

5.     There is no complete path along which electric current can flow from one terminal of dry cell through the wires and back to another terminal.

COMPONENTS IN AN ELECTRIC CIRCUIT

1.     The main components in an electric circuit are as follows:

a.      dry cell (battery)

b.     Bulb.

c.     Connecting wires.

d.     Switch..

2.     The function and symbol of each component in an electric circuit are shown in table below.

Components	Function	Symbol
Dry cell	Supplies electrical energy
Bulb	Produces light
Connecting wires	·        Connect components in electric circuit. ·        Conduct electrical energy.
Switch	Connect and breaks electrical circuit

DRAWING CIRCUIT DIAGRAMS

1.     We can draw the circuit diagram by using symbol for each component in an electric circuits.

2.     These diagrams tell us how the components are connected in a circuits.

3.     The ways to draw different electric circuits are shown in table below.

Electric circuit	Diagram