Grade 9 Unit D: Curriculum Links | Print |

Unit D: Electrical Principles and Technologies
(Science and Technology emphasis)

Current electricity provides the means to energize many devices, systems and processes that are part of our technological environment. Electricity, in combination with these technologies, is used to transfer energy, to provide mechanisms for control and to transmit information in a variety of forms. In this unit, students learn the principles that underlie electrical technologies by studying the form and function of electrical devices and by investigating ways to transfer, modify, measure, transform and control electrical energy. Using a problem-solving approach, students create and modify circuits to meet a variety of needs. Students develop skills for evaluating technologies by comparing alternate designs and by considering their efficiency, effectiveness and environmental impact.

This unit builds on ideas introduced in Grade 8, Unit D: Mechanical Systems, and introduces ideas that will be developed further in Science 10, Unit B: Energy Flow in Technological Systems, and in Science 30 Unit C: Electromagnetic Energy.

Focussing Questions:

How do we obtain and use electrical energy?

What scientific principles are involved?

What approaches can we use in selecting, developing and using energy-consuming devices that are efficient and effective in their energy use?

Key Concepts

  • forms of energy
  • energy storage
  • energy transformation
  • energy transmission
  • generation of electrical energy
  • measures and units of electrical energy
  • electric charge and current
  • electrical resistance and Ohm's law
  • circuits
  • renewable and nonrenewable energy

STS and Knowledge Outcomes

Students will:

Investigate and interpret the conversion of energy in devices involving electrical, chemical, thermal (heat) and other forms of energy

Identify, describe and interpret examples of chemical, thermal (heat) and electrical energy.

Investigate and describe evidence of energy transfer and transformation (e.g. electrical energy transferred through power grids; electrical energy converted to chemical energy in a flashlight, thermal energy converted to electrical energy in a thermocouple).

Investigate and evaluate the use of different chemicals, chemical concentrations and designs for electrical storage cells (e.g. build and test different forms of wet cells).

Construct, use and evaluate devices for transforming mechanical energy into electrical energy and for transforming electrical energy into mechanical energy.

Modify the design of an electrical device, and observe and evaluate resulting changes (e.g. investigate the effect of changes in the orientation and placement of magnets, commutator and armature in a St. Louis motor, or in a personally-built model of a motor).

Students will:

Describe technologies for transfer and control of electrical energy

Assess the potential danger of electrical devices by referring to the voltage and amperage of the device, and distinguish between safe and unsafe activities.

Distinguish between static and current electricity and identify example evidence of each.

dentify electrical conductors and insulators and compare the resistance of different materials to electric flow (e.g. compare the resistance of copper wire and nichrome wire; investigate the conduction of electricity through different solutions; investigate applications of electrical resistance in polygraph or "lie detector" tests).

Use switches and resistors to control electrical flow, and predict the effects of these and other devices in given applications (e.g. investigate and describe the operation of a rheostat).

Describe, using models, the nature of electrical current, and explain the relationship between current, resistance and voltage (e.g., use a hydro-flow model to explain current, resistance and voltage).

Measure electrical resistance, and predict current flow, using Ohm's law (e.g., measure the different resistances of copper wire, nichrome wire, pencil leads and salt solution).
[ Prerequisite Skill: Grade 8 Mathematics, Patterns and Relations, SO 5 ]

Develop, test and troubleshoot circuit designs for a variety of specific purposes, based on low voltage circuits (e.g. develop and test a device that is activated by a photoelectric cell, develop a model hoist that will lift a load to a given level, then stop and release its load, test and evaluate the use of series and parallel circuits for wiring a set of lights).

Investigate toys, models and household appliances, and draw circuit diagrams to show the flow of electricity through them (e.g., safely dismantle discarded devices such as heating devices or motorized toys and draw diagrams to show the loads, conductors, and switching mechanisms).

Identify similarities and differences between microelectronic circuits and circuits in a house (e.g., compare the uses of switches in a house and transistors in a micro-circuit).

Students will:

Identify and estimate energy inputs and outputs for example devices and systems, and evaluate the efficiency of energy conversions identify the forms of energy inputs and outputs in a device or system

Apply appropriate units, measures and devices in determining and describing quantities of electrical and heat energy (e.g., measure, estimate or calculate the quantity of energy transformed by an electrical device).
[Prerequisite Skill: Grade 8 Mathematics, Patterns and Relations, SO 51]

Apply the concepts of conservation of energy and efficiency to the analysis of energy devices (e.g., identify examples of energy dissipation in the form of heat, and describe the effect of these losses on useful energy output).

Compare energy inputs and outputs of a device, and calculate its efficiency (e.g., given information on electrical consumption and work output of a motor-driven device, compare the number of joules of energy used, with the number of joules of work produced).
[Prerequisite Skill: Grade 8 Mathematics, Patterns and Relations, SO 14,151]

Investigate and describe techniques for reducing waste of energy in common household devices (e.g., by eliminating sources off friction in mechanical components, using more efficient forms of lighting, reducing overuse of appliances as in "overdrying" of clothes).

Students will.
Describe and discuss the societal and environmental implications of the use of electrical energy

Identify and evaluate alternative sources of electrical energy, including oil, gas, coal, biomass, wind, waves and batteries (e.g., identify renewable and nonrenewable sources for generating electricity; evaluate the use of batteries as an alternative to internal combustion engines).

Describe the by-products of electrical generation and their impacts on the environment (e.g., identify by-products and potential impacts of coal-fired electricity generation).

Identify example uses of electrical technologies, and evaluate technologies in terms of benefits and impacts (e.g. identify benefits and issues related to the use of electronic technologies for storing and transmitting personal information).

Identify concerns regarding conservation of energy resources, and evaluate means for improving the sustainability of energy use.