Lesson Notes By Weeks and Term v5 - Grade 10

Lesson Video

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Performance objectives

• Identify and draw symbols for common electrical components.
• Explain the function of each component.
• Differentiate between component types (e.g., fixed vs. variable resistors).
• Interpret basic circuit diagrams.
• Apply Ohm's Law in simple series circuits.

Lesson summary

Welcome, Grade 10 Electrical Technology students! This week, we're diving into the fundamental building blocks of all things electrical: basic electrical components and their symbols. Understanding these components and their symbols is crucial because they form the language of electrical circuits. Just like you need to understand the alphabet to read and write, you need to understand these components to understand and design electrical circuits. From the simple lighting circuits in your homes to the complex systems powering Eskom's grids, all electrical systems are built from these basic elements.

Lesson notes

2.1 Resistors: Definition: A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. Resistors are used to reduce current flow, divide voltage, adjust signal levels, bias active elements, and terminate transmission lines, among other uses.

Symbol: The standard symbol for a resistor is a zigzag line (SA standard) or a rectangle (international standard, also acceptable). [Insert ASCII art or image link of both zigzag and rectangle resistor symbols] Function: Resistors limit the flow of current in a circuit. The higher the resistance value (measured in Ohms, Ω), the more the current is limited.

Types: Fixed Resistors: Have a fixed resistance value, usually indicated by color bands.

Variable Resistors (Potentiometers): Have a resistance value that can be adjusted manually (e.g., volume control on a radio). The symbol looks like a regular resistor with an arrow pointing to the zigzag line.

Thermistors: Resistance changes with temperature. NTC thermistors decrease in resistance as temperature increases; PTC thermistors increase in resistance.

Light Dependent Resistors (LDRs): Resistance changes with light intensity. Resistance decreases as light intensity increases.

Color Code: Resistor color codes indicate the resistance value and tolerance. (e.g., Brown Black Red Gold = 10 x 10^2 Ω ± 5% = 1000 Ω ± 5%) We will cover colour code interpretation in detail later. 2.2 Capacitors: Definition: A capacitor is a passive two-terminal electrical component that stores electrical energy in an electric field.

Symbol: Two parallel lines, either straight or curved (for electrolytic capacitors, the curved line indicates the negative terminal). [Insert ASCII art or image link of both capacitor symbols] Function: Capacitors store electrical energy. They are used for filtering, smoothing voltage, and energy storage.

Types: Ceramic Capacitors: Non-polarized, small capacitance values, used for high-frequency applications.

Electrolytic Capacitors: Polarized (have positive and negative terminals), larger capacitance values, used for filtering and smoothing.

Film Capacitors: Non-polarized, good stability and low loss. 2.3 Inductors: Definition: An inductor is a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it.

Symbol: A coil of wire. [Insert ASCII art or image link of inductor symbol] Function: Inductors resist changes in current flow. They are used for filtering, energy storage, and in resonant circuits.

Unit: Henry (H) 2.4 Diodes: Definition: A diode is a two-terminal electronic component that conducts primarily in one direction (asymmetric conductance); it has low (ideally zero) resistance to current in one direction, and high (ideally infinite) resistance in the other.

Symbol: A triangle pointing towards a vertical line. [Insert ASCII art or image link of diode symbol] Function: Allows current to flow in only one direction. Used for rectification (converting AC to DC) and signal control.

Types: Rectifier Diodes: Used for converting AC to D

C. Light Emitting Diodes (LEDs): Emit light when current flows through them. The symbol is the same as a diode, but with two arrows pointing away from the diode. 2.5 Transistors: Definition: A semiconductor device used to amplify or switch electronic signals and electrical power.

Symbol: There are two main types: Bipolar Junction Transistors (BJTs) and Field-Effect Transistors (FETs). The symbols differ. Focus on NPN and PNP BJT. [Insert ASCII art or image link of NPN and PNP BJT transistor symbols] Function: Amplifies or switches electronic signals.

Types: Bipolar Junction Transistors (BJTs): Controlled by current at the base terminal.

Field-Effect Transistors (FETs): Controlled by voltage at the gate terminal. 2.6 Switches: Definition: A switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another.

Symbol: A line with a break that can be closed or open. [Insert ASCII art or image link of switch symbols - SPST, SPDT] Types: Single Pole Single Throw (SPST): Simple on/off switch.

Single Pole Double Throw (SPDT): Can switch a circuit to one of two paths.

Double Pole Single Throw (DPST): Two SPST switches controlled by a single mechanism.

Double Pole Double Throw (DPDT): Two SPDT switches controlled by a single mechanism. 2.7 Voltage and Current Sources: Definition: Voltage source provides a constant voltage, while a current source provides a constant current.

Symbol: A circle with a plus and minus sign inside (voltage source) or a circle with an arrow inside (current source). [Insert ASCII art or image link of voltage and current source symbols] Function: Provides electrical power to the circuit. 2.8 Ohm's Law: Formula: V = IR, where V is voltage (in Volts), I is current (in Amperes), and R is resistance (in Ohms).