Integrated Science

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WEEK 1                      LESSON 1

BASIC ELECTRONICS 

ELECTRONICS is the branch of science that deals with the behaviour and the flow of electrons in semi-conductors , vacuums or gases .  

OR 

ELECTRONICS is the branch of science that deals with design and application of devices whose operation depends on the flow of electrons.  

 

ELECTRONICS DEVICES 

ELECTRONICS DEVICES are devices that make use of the flow of electrons in their operation. 

OR 

They are devices made using electronics.  

 

EXAMPLES OF ELECTRONICS DEVICES 

1. Mobile phones 

2. Computers  

3. Television set 

4. Radio sets  

5. Microwave  

6. Electric fans. Etc. 

ELECTRONICS COMPONENTS 

1. Light Emitting Diode ( LED) 

 

 

2. PN Junction diode 

 

 

 

3. Capacitor  

 

 

 

4. Resistor  

  

5. A cell 

 

 

6. A transistor  

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ELECTRONICS COMPONENTS, FUNCTIONS AND CIRCUIT SYMBOLS.

1.       Light Emitting Diode ( LED)

FUNCTION

It converts or changes electrical energy to light energy. 

ELECTRONICS CIRCUIT SYMBOL

 

2.       PN Junction diode 

FUNCTION

It allows electric current or charges to flow in only one direction. 

ELECTRONICS CIRCUIT SYMBOL 

3.       Resistor 

FUNCTION

It opposes the flow of current or electricity. 

ELECTRONICS CIRCUIT SYMBOL

 

4.       Capacitor 

FUNCTION

It store electric charges temporarily. 

ELECTRONICS CIRCUI SYMBOL

 

5.       Cell

FUNCTION

It converts chemical energy to electrical energy. 

ELECTRONIC CIRCUIT SYMBOL

 

NB. Battery is the connection of two or more cells.

6.       A transistor 

A transistor is a three terminal semi-conductor device usually used as an amplifier or a switch. 

Parts of a transistor.

A transistor is made up of three parts. These are; 

1.       Emitter ( the negative terminal) : It ejects electrons to the base.

2.       Base ( the neutral terminal) : It passes electrons to the collector.

3.       Collector ( the positive terminal ) : It receives electrons from the base.

 Types of transistors

There are two main types of transistors. These are ;

1.       PNP transistor: It has more hole ( protons) than electrons. 

ELECTRONICS CIRCUIT SYMBOL

 

2.       NPN transistor: It has more electrons than holes ( protons).

ELECTRONICS CIRCUIT SYMBOL

USES OF A TRANSISTOR 

1.       It is used as an amplifier. 

2.       It is used as a switch. 

3.       It is used to discharge a Capacitor. 

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SEMI-CONDUCTORS

A Semi-conductor is a material whose electrical conductivity lies between a conductor and an insulator. 

• A semi- conductor conducts electricity using electrons ( negative charges) and holes  ( positive changes)

NB:  A Semi-conductor in its pure or intrinsic state has equal number of electrons and holes.

Examples of Semi-conductor

1. Silicon 

2. Germanium 

3. Arsenic

4. Indium, etc.

DOPING

Doping is the process of adding impurities or foreign elements to a semi- conductor in order to make it conduct electricity well.

• When a Semi-conductor is doped, the number of electrons and holes become unequal. 

• When a Semi-conductor is doped either a p-type semi-conductors or n-type semi-conductors are formed.

Types of a Semi-conductor

1. A p-type semi-conductor: It is a semi-conductor that conducts electricity mainly by holes ( positive charges).

• It has excess holes. 

• It is formed by doping a Semi-conductor with a trivalent element ( elements with three valence electrons). Eg. Boron (B).

2. A n- type semi-conductor: it is a semi-conductor that conducts electricity mainly by electrons (negative charges ).

• It has excess electrons. 

• It is formed by doping a Semi-conductor with a pentavalent element (elements with five valence electrons). Eg.  Phosphorus (P).

A P-N Junction

A p-n junction is the boundary formed when p- type semi-conductor and n-type semi-conductor are joined.

• A p-n junction is used in the operation of devices such as transistors and a diodes.

NB: A transistor has two ( 2 ) P-N JUNCTIONS. 

BIASING

Biasing is the process of connecting the p-type semi-conductor and the n-type semi-conductor across a voltage ( the terminal of a battery).                 

   

OR

Biasing is the process of connecting the p-type block or region  and the n-type block or region of an electronic component across a voltage ( the terminal of a battery).

Types of Biasing

1. A forward bias

A forward bias is when the p-type semi-conductor is connected to the positive terminal of a battery and the n-type semi-conductor is connected to the negative terminal of a battery. 

• In forward bias circuit, electrical current flows.

2. A reverse bias 

A reverse bias is when the p- type semi-conductor is connected to the negative terminal of a battery and the n-type semi-conductor is connected to the positive terminal of a battery. 

• In reverse bias circuit, no electrical current flows.

  

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CHEMICAL ELEMENTS 

LESSON 1. 

An element is a simple chemical substance that consists of atoms of only one  kind or the same kind. 

OR 

An element is a substance that can not be broken down into simpler  substances by chemical means. 

OR 

An element is a substance that contains two or more atoms of the same kind 

PROPERTIES OF ELEMENTS 

1. Elements cannot be broken down into simpler substances by chemical  means.  

2. Elements combine in different ways to form compound  3. Elements are made up of different density.  

4. Elements can be either solid, liquid or gas. 

CHEMICAL SYMBOLS 

A chemical symbol is an alphabet or letter(s ) to represent an element.  OR 

It is the use of a letter or two to represent an element . 

NB:  

- If a letter or an alphabet is used to represent an element, it should be  written in capital. Eg. Hydrogen (H)

- If two letters or alphabets are used, the first letter should be written in  capital and the second in lower case. Eg. Helium (He). 

Note: 

1. Presently, there are about 114 known chemical elements in the world  - Some of the elements are natural ( they occur naturally on earth and in  organisms) and some are artificial ( created by scientists). 

2. Chemical elements or simply elements are represented by by chemical  symbols.  

- The symbol of chemical elements can be a letter or two taken from  English, Latin, Greek , French, Swedish and Spanish.  

ELEMENTS, LATIN NAMES AND CHEMICAL SYMBOLS 

Elements Latin names or other  names. 

Chemical symbols  

Rhymes Atomic  number 

NB: Mercury and Bromide are liquid at room temperature. 

ATOMS 

An atom is the smallest particles of an element or matter that takes part in a  chemical reaction.  

STRUCTURE OF AN ATOM 

- An atom is made of central part called nucleus . 

- In the nucleus are protons and neutrons. 

- Outside/ around the nucleus are electrons revolving in their orbits . - The protons are positively charged particles.  

- The electrons are negatively charged particles.  

- The neutrons have no charge. 

Summary 

ATOMIC STRUCTURE 

SUB - ATOMIC PARTICLES 

Sub- atomic particle are particles that make up atoms. 

Sub- atomic  particles  

Symbols Masses Charges Location  

1. Protons P 1 +1 Inside the  nucleus . 

2. Electrons e- 1/1840 -1 Outside  the  

nucleus. 

3. Neutrons N 1 0 Inside the  nucleus. 

DIFFERENCES BETWEEN PROTONS AND ELECTRONS. Protons Electrons  

1. They are positively charged  particles . 

They are negatively charged particles. 

2. They are inside the nucleus . They are outside the nucleus.  3. They have atomic mass of 1. They have mass of 1/1840. 

Why atoms are electrically neutral or have no charge. 

Atoms are electrically neutral because the number of proton (+1) and the  number of electrons (-1) are equal and therefore their charges cancel out.