Lesson Notes By Weeks and Term - Junior Secondary 3

Basic electronics I



Class: Junior Secondary School 3

Age: 14 years

Duration: 40 minutes of 5 periods each




SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

  1. Identify basic electronic components
  2. Define electron emission
  3. Identify the types of electron emission
  4. Identify the types of electronic devices.

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers,

demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures,









The teacher Identify the basic electronic components and state their uses

Students pay




Teacher explains electron emission and discusses it's types.

Students pay

attention and




Teacher discusses the types of basic electronic devices

Students pay

attention and




The teacher writes a summarized

note on the board

The students

copy the note in

their books




Basic electronic components include:

  1. Resistor: Restricts the flow of electric current.
  2. Capacitor: Stores and releases electrical energy.
  3. Inductor: Stores energy in a magnetic field when current flows through it.
  4. Diode: Allows current to flow in one direction only.
  5. Transistor: Amplifies or switches electronic signals.
  6. Integrated Circuit (IC): Miniaturized arrangement of transistors, resistors, and capacitors on a single chip.
  7. Voltage Regulator: Maintains a stable voltage output.
  8. Battery: Stores electrical energy.
  9. LED (Light Emitting Diode): Emits light when current flows through it.
  10. Switch: controls the flow of electricity by opening or closing a circuit.

Basic Emission Theory

Electron emission refers to the process in which electrons are expelled or released from a material or surface. There are several mechanisms through which electron emission can occur:

  1. Thermionic Emission: Here electrons are emitted from a material when it is heated. The heat provides enough energy to overcome the material's work function, allowing electrons to escape.
  2. Field Emission: In field emission, electrons are emitted by a material in the presence of a strong electric field. This mechanism is common in nanoscale structures, where the electric field is sufficient to overcome the material's work function.
  3. Photoelectric Emission: Electrons are emitted from a material when it is exposed to light or electromagnetic radiation. The incident photons transfer energy to electrons, enabling them to overcome the work function and be emitted.
  4. Secondary Emission: In secondary emission, the electrons are released from a material when it is bombarded by high-energy electrons, ions, or photons. This secondary emission is often utilized in devices like photomultiplier tubes.
  5. Cold Emission (Field Electron Emission): Electrons are emitted at room temperature or lower temperatures in the presence of a strong electric field. This phenomenon is observed in specific materials with high field-enhancement factors.

Types of Basic Electronic Devices

The basic electronic devices are the devices which emit and control the movement of electrons in a desirable manner used in generation of electronic appliances. The following are the types of basic electronic devices:

  1. Semi-Conductors: Semi-conductors are those substances whose electrically conductivity lies between the good conductors (metallic substances) and good insulators (non-metallic substances) E.g. Silicon, Germanium.
  2. Resistor: A Resistor is a device used to control the flow of electric current in an electric circuit or which opposes the flow of electric circuit. The ability of a Resistor to control the flow of electric current is called RESISTANCE. The resistor is measured in Ohms by a device called Ohm meter
  3. Capacitors: A capacitor is a piece of an apparatus designed to store electrical energies in the form of electric charges. An example of capacitor is Condenser or starter in a fluorescent lamp. The capacitors are available in motor vehicles and air conditioner etc.
  4. Capacitance: This is a phenomenon which exists when certain parts of an electric circuit are able to store electric charges.

Capacitance (C) = Charge on either plate (Q)/P.d across the plates (V).

The S.I unit of a capacitance is farad (F)

  1. Transistors: Transistors are semi-conductor materials which are capable of providing amplification in electronic equipment. They are smaller than vacuum tubes; the vacuum tubes control the flow of electron in the airless space while the transistors control the flow of electrons in the semi-conductors materials.

Transistor has three electrodes in terminals

  1. The Emitter (E)
  2. The Base (B)
  3. The Collector (C)

The types of transistors are:

  1. NPN Transistor: Consists of three layers: the N-type semiconductor (negative), the P-type semiconductor (positive), and another N-type semiconductor.When a small current flows into the base (P-type), it controls a larger current flowing between the collector (N-type) and the emitter (N-type), allowing for signal amplification.
  2. PNP Transistor: Similar to the NPN transistor but with the layers reversed: P-type semiconductor, N-type semiconductor, and another P-type semiconductor.The flow of current and signal amplification occurs in the opposite direction compared to NPN transistors.

EVALUATION: 1. What is electron emission?

  1. Identify and explain 4 types of electron emission
  2. Identify 10 basic electronic components and state their uses.

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively