Electronics Basics

Introduction

Electricity is a fundamental force of nature that powers our modern world. At its core, electricity involves the movement of electrons through a conductive material, creating a flow of electrical charge.

Materials and Conductivity

1. Conductor

A material that allows electric current to flow easily through it due to loosely bound electrons that are free to move within the material in response to an applied electric field.

Examples: Copper, aluminum, gold, silver

2. Insulator

A material that does not easily allow the flow of electric current. Insulators have high electrical resistance, which impedes the movement of electric charge (electrons) through them.

Examples: Rubber, glass, plastic, wood

3. Semi-Conductor

A material with electrical conductivity between that of a conductor and an insulator. Their conductivity can be significantly altered by introducing impurities (doping) or by applying external electrical fields.

Types:

• Intrinsic Semiconductor: Pure semiconductors without intentional doping (e.g., pure silicon, germanium)
• Extrinsic Semiconductor: Intentionally doped semiconductors
  • N-type: Doped with elements having more valence electrons (e.g., phosphorus, arsenic)
  • P-type: Doped with elements having fewer valence electrons (e.g., boron, aluminum, gallium)

Types of Electricity

Static Electricity

The accumulation of electric charge on the surface of an object due to friction or induction. Does not flow as a current but can cause sparks or electrostatic discharge.

Applications: Photocopiers, air purification systems

Dynamic Electricity

Electricity involving the flow of electric charge as a current, where electrons move through a conductor due to applied voltage or EMF.

1. Direct Current (DC)

Electrons flow consistently in one direction through a conductor.

Applications: Batteries, electronic devices, electric vehicles, telecommunications

2. Alternating Current (AC)

The flow of electrons periodically reverses direction at a specific frequency (e.g., 50 or 60 Hz), resulting in a sinusoidal waveform.

Applications: Power transmission and distribution, homes, businesses, industries for powering appliances, lighting, motors, and machinery

Elements of Electricity

1. Electric Charge

A fundamental property of matter that describes the presence of electrical force. It is associated with subatomic particles - protons and electrons.

Key Points:

• Protons: Positively charged (+e ≈ 1.602 × 10⁻¹⁹ coulombs)
• Electrons: Negatively charged (-e)
• Atoms are electrically neutral (equal protons and electrons)
• Like charges repel, unlike charges attract
• Unit: Coulomb (C) ≈ 6.24 × 10¹⁸ elementary charges

2. Voltage

Electric potential difference - the force or pressure that drives electric charge to flow in an electrical circuit. It measures the potential energy difference per unit charge between two points in an electric field.

Key Points:

• Unit: Volt (V)
• 1 volt = 1 joule/coulomb (1 V = 1 J/C)
• Supplied by voltage sources (battery, generator, power supply)
• Measured across components using a voltmeter
• Higher voltage results in greater potential energy and higher current through given resistance

Formula: V = IR (Ohm's Law)

3. Current

The flow of electric charge through a conductor - the rate of movement of electric charge past a given point in a circuit.

Key Points:

• Symbol: I
• Unit: Ampere (A)
• 1 ampere = 1 coulomb/second (1 A = 1 C/s)
• Direction: By convention, from positive to negative terminal (opposite to electron flow)
• Amount depends on applied voltage: I = V/R (Ohm's Law)

Formula: I = Q/t
Where:

• I = electric current (amperes)
• Q = charge (coulombs)
• t = time (seconds)

4. Resistance

Opposition encountered by electric current as it flows through a conductor. It measures how difficult it is for charges (electrons) to move through a material when subjected to an electric potential difference (voltage).

Key Points:

• Symbol: R
• Unit: Ohm (Ω)
• Caused by collisions between charge carriers and atoms
• Affected by material type, length, cross-sectional area, and temperature

Formula: R = V/I (Ohm's Law)

Electrical Circuits

An electric circuit is a closed pathway or loop through which electric current can flow. It consists of electrical components (voltage sources, conductors, resistors, capacitors, inductors, switches) interconnected by conductive wires or traces.

Types of Circuits

1. Series Circuit

• Only one current path
• Same battery current flows through each component
• A breakage in the path ceases function of all equipment
• Total resistance: R_total = R₁ + R₂ + R₃ + ...

Characteristics:

• Current is same throughout
• Voltage divides across components
• Total voltage = sum of individual voltage drops

2. Parallel Circuit

• More than one current path
• Current splits up with greater current flowing through smallest resistance
• A breakage in any one path does not interfere with operation of remainder of units

Characteristics:

• Voltage is same across all branches
• Current divides among branches
• Total current = sum of branch currents
• Reciprocal of total resistance: 1/R_total = 1/R₁ + 1/R₂ + 1/R³ + ...

Voltage Generation Methods

1. Electromagnetic Induction

When a conductor moves through a magnetic field at right angle to the lines of magnetic force, voltage is induced in the conductor.

Key Points:

• Discovered by Michael Faraday (1831)
• Voltage increases with: stronger magnetic field, faster motion
• Used in: Generators and alternators

2. Electrochemical Cell

Devices that generate electrical energy from chemical reactions (galvanic/voltaic cells) or facilitate chemical reactions using electrical energy (electrolytic cells).

Example: Standard 1.5V batteries for TV remotes, clocks

3. Heat (Thermoelectric Effect)

Voltage produced at the junction where two unlike metals are joined, with one at high temperature and another at low temperature. The temperature difference causes electron flow and voltage development.

Application: Thermocouples

4. Light (Photoelectric Effect)

Voltage produced when light strikes photosensitive substances. Changes in light intensity or wavelength produce corresponding changes in current, voltage, or resistance.

Application: Photoelectric cells, solar panels

5. Pressure (Piezoelectric Effect)

Piezoelectric substances generate energy through mechanical stress (compression, expansion, or twisting), resulting in an electric charge.

Application: Piezoelectric sensors, igniters

Ohm's Law

The fundamental relationship between voltage, current, and resistance:

V = I × R

Where:

• V = Voltage (volts)
• I = Current (amperes)
• R = Resistance (ohms)

Derived forms:

• I = V/R
• R = V/I