Grade 7 Technology (TECH) Summaries – Term 3 (Spot On)

This document provides summaries for Grade 7 Technology, Spot On, Term 3, Module 5: Electrical systems and control.

Module 5 Overview

The module covers:

• Magnetism: Types of magnets and materials with magnetic qualities.
• Recycling: Including the 5 R’s of conservation.
• Electrical Systems: Simple electric circuits, cells, batteries, and electromagnets.
• Complex Machinery: Cranks and pulleys, and strengthening frame structures (triangulation).

Key Concepts

• Magnetism: Magnetite is a natural rock that attracts iron. Magnets have a magnetic field (area where force is felt) and poles, with opposite poles attracting.
  • Types: Permanent magnets are always magnetic, while temporary magnets (electromagnets) are only magnetic with an electric current.
• Electromagnets: Created when electric current flows through a coil of insulated wire around an iron bar, strengthening the magnetic field. The magnetism can be switched on and off, making them useful for lifting iron scrap metal. A solenoid is a coil of wire carrying an electric current that acts like a magnet.
• Circuits: A circuit is the path electricity follows. Electricity flows only in a closed circuit, and an open circuit stops the flow. Basic circuits require a source of energy (cell/battery), conductors, a switch, and a device that uses electricity.
• Recycling (The 5 R’s): Reduce, Recycle, Reuse, Renew, and Repair. Sorting scrap metal is important for efficiency and increases its value. Ferrous materials contain iron.
• Complex Machinery:
  • Crank: An adaptation of a lever used to transmit rotary (turning) motion.
  • Pulley: A type of wheel and axle with a groove for a rope or belt. A single pulley changes the direction of force but does not give mechanical advantage.
  • Cranes: Rely on mechanical and electrical principles, use levers/pulleys, and are strengthened using triangulation.