Course Profile   Science, Grade 9 academic, Public

 

Unit 4:  Physics: The Characteristics of Electricity

 

Activity 1 | Activity 2 | Activity 3 | Activity 4 | Activity 5 | Activity 6

Time:  22 hours

Unit Description

Students gain an understanding of basic electricity through a study of static and current electricity. Using a variety of instruments and tools, they develop skills in gathering qualitative and quantitative data. They use the relationships among current/electrical resistance/potential difference, and energy/power/time to solve simple problems. Students apply their knowledge to the design and construction of an electrical circuit that performs a specific function. Safety concerns related to static and current electricity in daily life, and the safe use of electrical equipment, are addressed. Students evaluate social, economic, and environmental costs and benefits associated with electrical energy production and distribution in Canada.

Strand(s) and Expectations

Strand(s):  Physics

Overall Expectations:  PHV.01, PHV.02, PHV.03.

Specific Expectations:  PH1.01 to .13, PH2.01 to .11, PH3.01 to .03.

Activity Titles (Time and Sequence)

Activity 1

Our Electrical World

60 minutes

Activity 2

Current Electricity

360 minutes

Activity 3

Electrical Energy Production

360 minutes

Activity 4

Static Electricity

120 minutes

Activity 5

Simple Home Circuits

210 minutes

Activity 6

End-of-Unit Culminating Task

210 minutes

Depending on student interest, or even on the humidity, the static electricity activity can stand-alone and may be moved from the above sequence.

Prior Learning Required

Students have some background knowledge of electricity from their Grade 6 Science and Technology program. They are familiar with terms such as load, source, switch, conductor, insulator and parallel and series circuit. Static electricity was introduced in Unit 1 (Weird Water) of this course, which provided an opportunity to assess the knowledge and skills acquired prior to Grade 9. Diagnosis of prior learning should continue throughout the content of this unit. Students have developed inquiry skills - both research and experimentation - in previous units, and also have gained experience in several different modes of communication (e.g., oral presentation, several forms of written reports, demonstration using concrete materials, diagrams, use of models, etc.).

The teacher reinforces safety cautions noted by students from their earlier years. Stress should be on personal safety and the appropriate use of equipment.

Unit Planning Notes

The static electricity demonstrations require dry conditions for excellent results. Activity 4 is best done in the dry winter months. Static electricity is defined in this unit as the separation of charges, often by friction, and usually associated with a high voltage. Energy, often provided by friction between dissimilar materials, is required to separate the charges.

Some precautions on safety include the following:

·         students are to instructed in the safe and proper operation of electrical equipment, especially equipment involving voltages over 24 V (individual human tolerance varies greatly);

·         only CSA approved electrical equipment should be used;

·         equipment should be checked to ensure connections are tight and that there are no damaged or loose wires;

·         all electrical circuitry must be checked by the teacher before the switch is closed where there is the possibility of harm to students or damage to electrical equipment;

·         students should be warned that dry cells may explode if shorted out (short circuited);

·         wires which short circuit dry cells become extremely hot and may cause burns when touched, or fires if in contact with flammables;

·         refer to general safety procedures outlined in Part 1, Program Outline and Policy (Science, Intermediate and Senior Divisions, 1987) or to safety resources available through the Science Teachers Association of Ontario (STAO).  The STAO web site at http://www.stao.org/safety.htm has information on safety publications, articles from Crucible and links to other safety sites.

Although not strictly required by specific expectations, Activity 5.4 is an extension that offers students a valuable opportunity to apply their learning to practical household wiring.

A Note on Science Fairs

This unit provides opportunities for students to begin open-ended, experimental inquiry. When they have access to a science fair, students should be encouraged to present their findings there for a variety of reasons: preparation for a science fair requires self-assessment based on clearly-stated criteria; presenting to an alternative audience deepens understanding of the topic; judges are able to provide expert feedback on both process and product; and wider recognition of good work may motivate students to pursue further inquiry.

Teaching/Learning Strategies or Activities

Activity

Strategy

Description

1

Bell-ringer lab; group brainstorming

Rotation through stations of electrical equipment/appliances to assess prior knowledge; groups develop questions and a recording device for what they know and want to learn about electricity

2

Laboratory activity; data collections and interpretation; solving exercises; inquiry

Build various circuits; make voltage and current measurements; plot and interpret graphs; solve exercises on Ohm’s law and related principles; perform an experimental inquiry on a testable question they develop

3

Teacher-directed lesson; research project and presentation; develop and defend a plan. Optional field trip and/or guest speaker.

Discussion of alternate energy sources for electrical production, with risks and benefits; library/resource centre research project on an alternate method; develop a plan to power a confined site off the grid using alternate energy sources.

4

Teacher demonstration; student lab activity

Demonstration of static phenomena using high static voltage equipment; students use electron transfer to explain electrostatic phenomena

5

Lab activities; teacher demonstrations; problem solving

Groups observe a simulated-variable resistor in a circuit and a demonstration of heat from a resistance; groups problem solve the wiring in a 3-way switch (optional 4-way switch); optional activity doing wiring of house circuit components

6

Design, construct, and evaluate a circuit to perform a function

Students define a suitable challenge for which they design, build, test, and evaluate an electrical circuit to perform a function.

 

Assessment / Evaluation

Activity

Assessing and Evaluating

Method or Instrument

1

Understanding concepts; group brainstorming;

Rubric on collaborative group work; assess group recording device and presentation for concept attainment

2

Use of equipment; measurement; data management; mathematical exercises;

Direct observation of use of meters and equipment; rubrics or checklists to assess schematics, charts, graphs, and slope calculations for measurements and concepts; quiz on Ohm’s Law and efficiency exercises.

3

Note making; research skills; presentation skills; group work

Review notebooks for completeness and accuracy of content; rubric on Inquiry-Research and on written reports; rubric on presentations (Geography profile); rubric on collaborative group work

4

Understanding of concepts;

Graffiti chart or concept map; checklist for accuracy of diagrams of conduction and induction

5

Understanding of concepts; problem solving

Notebooks and schematic diagrams; direct observation of problem solving with circuits (3-way and 4-way switches)

6

Design and construct

Rubric to assess process and product

Resources

The following Internet sites contain information from Ontario Hydro on safety codes and the Ontario power generation system:

http://www.esainspection.net/main.html

http://www.ontariopowergeneration.com

The site below lists energy information for common appliances

http://energuide.nrcan.gc.ca/

The same information is available in the book EnerGuide, available from various hydro offices.

Commercial surge protection devices are available not only for individual electrical outlets but for cable television, telephone, and hydro lines in homes. Advertising information about the devices may be useful in a discussion of static electricity, particularly lightning.

The Office of Energy Efficiency of Natural Resources Canada c/o Canada Communication Group, Ottawa, ON K1A 0S9 has publications such as Air Conditioning Your Home; Household Lighting; Comparing Heating Costs; How Can Energy-efficient Appliances Save You Money?

 

Activity 1:  Our Electrical World

 

Time:  60 minutes

Description

This activity begins the unit focus on the basic principles that determine how electricity works by examining a number of electrical devices. It requires students to ask questions and to think about ways to answer them. Some of the questions generated are used in subsequent activities in this unit.  Others may be used in Unit 6, the culminating activity for the course.

Strand(s) and Expectations

Strand(s):  Physics

Expectations:  PH2.03.

Planning Notes

·         The activity allows students to demonstrate and teachers to assess prior learning. Depending on the student population and interest, the teacher may choose to follow this activity with either Activity 2 (focus on circuitry) or Activity 4 (focus on static electricity).

·         As students begin to ask questions, they may uncover the need for new learning. The teacher should be ready to redirect them as appropriate. For example, a circuit breaker discussion may lead to the use of bimetallic strips in thermostats; reference to electromagnets may lead to electromagnetism in motors and generators. Care must be taken to devote class time primarily to content described by the Expectations in the policy document while allowing individual students to pursue extension topics on their own time.

·         This unit provides many opportunities for students to work in co-operative small groups. Teachers should consult one of the excellent references available from commercial publishers and many boards of education to become familiar with the wide variety of Co-operative Small Group Learning (CSGL) strategies available. The OSSTF resource book Together We Learn is another good resource. A comprehensive review of CSGL structures and their application is presented in the Essential Science Course Profile, Appendix OV-3. This profile is available on the Ontario Curriculum Clearinghouse web site at http://www.curriculum.org.

Prior Learning Required

Refer to TSM - Ontario Curriculum, Grades 1-8, Science and Technology for prior knowledge.

Teaching/Learning Strategies

1.1 Student Activity:  The students work in groups to examine a variety of electrical devices and problems associated with the use of electricity. They consider questions such as: Why is it needed? How does it work? What information is needed to figure out how it works? Why is it designed that way? What caused the problem? etc.

Teacher Facilitation:  Set up a series of stations with devices or scenarios. Some samples include:

·         a household circuit breaker;

·         a circuit diagram/plan of the classroom - obtained from plant services or a school custodian (What do the symbols mean? Why are they wired in this fashion?)

·         carpet shock treatment devices/computer static problems, static electricity mats

·         static chains/straps (fuel trucks) (What do they prevent? Implications?)

·         lightning rods lightning as a phenomena

·         jumper cables (How should they be safely connected?)

·         extension cords (Why do they come in various lengths and wire gauges? Does length matter?)

·         electronic air cleaners

·         car batteries and lemon cells

·         electric motors and hand powered generators

·         sources of electrical energy (Where is the electricity coming from?)

1.2 Student Activity:  The students work on a graffiti chart or other form of brainstorming format to record their observations, ideas and questions. A set of instructions for using a graffiti chart is given following Activity 1.2 in Unit 5, Astronomy- Phase 1. A simple form is a KWL chart with three columns: what you know (K) about the device, what you want (W) to find out, and what you have learned (L - to be recorded as the unit progresses). Students then present their questions and ideas briefly to the class in a sharing activity. Students may enter a selection of the more interesting questions in their Science Journals or on the Wonder Wall.

Teacher Facilitation:  Guide and moderate the presentation/discussion from the graffiti charts. Highlight the questions generated and areas for further research with the intention of leading into the next activity. Questions for the Wonder Wall may arise from this activity.

Assessment / Evaluation Techniques

·         Teacher and/or students, using the rubric for collaborative group work (TSM page x- Phase 1) and the Achievement Chart for Science, can formatively assess students participation in the CSGL exercise.

Accommodations

·         Refer to TSM - Accommodations for Students with Special Needs (TSM page i - Phase 1)

Resources

Lewin, L. and B.J. Shoemaker. Great Performances: Creating Classroom-Based Assessment Task. USA: ASCD Publishers, 1998. ISBN 087120-339-1.

Macauley, David. The Way Things Work (book). USA: Houghton Mifflin, 1988. ISBN 039542-857-2

Macauley, David. The Way Things Work (CD). USA: Dorling Kindersley, 1998. ISBN 078941-253-5

 

Activity 2:  Current Electricity

 

Time:  360 minutes

Description

During the initial activity, students construct circuits and review prior knowledge of series and parallel circuits. They learn how to use ammeters and voltmeters (or multimeters) safely to make various readings in different types of circuits, first using light bulbs and then using ohmic resistors. Next, students solve mathematical problems involving relationships among different types of measurements in electric circuits. Students finish the series of activities by formulating a question to test, and designing and conducting an experiment to answer the question.

Strand(s) and Expectations

Strand(s):  Physics

Expectations:  PH1.04, PH1.05, PH1.06, PH1.07, PH1.08 PH1.09, PH1.10, PH1.11, PH1.12, PH2.01, PH2.02, PH2.03, PH2.05, PH2.06, PH2.07, PH2.08, PH2.11.

Planning Notes

Materials required for the activities include:

·         wires

·         light bulbs

·         alligator leads

·         6 V dry cells

·         variable voltage power pack

·         ammeters and voltmeters

·         ohmic resistors (of different resistance)

·         graph paper

·         teacher-prepared problems or a series of problems selected from a text

Optional:

·         ohmmeter

·         magnet-backed, cardboard cut-outs of electrical components for creating large schematic diagrams

Building series and parallel circuits is part of the Grade 6 curriculum. Until full implementation of the Grade 1-8 program, the amount of guidance, review and new teaching required in the activities change from year to year.

Prior to beginning the unit, the teacher may need to consult knowledgeable colleagues regarding the construction of series and parallel circuits and the correct use of ammeters, voltmeters, and ohmmeters. Seemingly simple errors can cause irreparable damage to equipment.

Prior Learning Required

Please refer to TSM- Phase 1- Ontario Curriculum, Grades 1-8: Science and Technology for a general overview and the document itself for details of previous learning.

Students use quantitative data to create and interpret graphs, including the calculation and physical interpretation of slope. Activity 4 of Unit 1 in both the Academic and Applied profiles for Mathematics relates to this type of graphical interpretation.

Exercises involving the manipulation of three variables are solved.

Teaching/Learning Strategies

2.1 Student Activity:  Given a 6 V power source, pieces of wire, four identical light bulbs and alligator leads, student groups build two different types of circuits, so that each lights two bulbs. They draw simple diagrams to represent their circuits and make qualitative comparison regarding the brightness of the light bulbs. They then share their constructed circuits with the class. Model circuits (series and parallel) are selected as examples for Activities 2.2 and 2.3. Students make notes, record definitions and/or examples of the following: source, load, series circuit, parallel circuit, current, characteristics of schematic drawings, and the basic symbols used in schematics.

Teacher Facilitation:  Review with students the past work they may have done building electric circuits, and challenge them to use the materials provided to create two different types of circuits that each light two bulbs. As they construct their circuits, travel about the class to encourage and provide guidance. Following the sharing session (e.g., show and tell; blackboard drawings) help students to develop a note to review the key concepts. At the same time establish some of the basic rules of schematic circuit diagrams (i.e., rectangular in nature; correct symbols for components - examples below) as the accepted way of representing circuits.

2.2 Student Activity:  Students observe a teacher demonstration to learn how to correctly connect an ammeter in a circuit and to perform a touch test to ensure safety of equipment prior to taking a measurement. Students use the ammeter to take readings at specific locations in the series and parallel circuits constructed in Activity 2.1. Challenged to explain what it is they have been measuring, the students take part in a teacher-led discussion of electric current. They record their readings and the location of their measurements in the circuits (using schematic drawings and the symbol for an ammeter) and record a working definition of current in their Science notebooks. They use the pattern of the measurements taken to write a general description of current flow in series and parallel circuits.

Teacher Facilitation:  Provide students with the correct symbol for an ammeter in a schematic diagram, and give them instructions for correctly connecting an ammeter in a circuit and then performing a touch test. The ammeter must always be connected in series, and before the last alligator clip is firmly attached, it is briefly touched to see that the needle moves forward and does not extend past the scale for the chosen range. Using a blackboard or overhead drawing/display of the series circuit, direct students to take ammeter readings at three specific locations as indicated in diagram 1 below. This procedure is then repeated with the parallel circuit, with readings taken at the six locations shown in diagram 2 below. (Note: Only one reading is taken at a time; the ammeter is then moved to the next location.)

                         

                            Diagram 1                                                              Diagram 2

Although there are limitations to its applicability, a water analogy may be useful to explain the concept of current flow. One reference for the water analogy is http://http.cs.berkeley.edu/~randy/Courses/CS39C.S97/telegraph/electricity.html. 

Many high school physics textbooks also address this analogy.

2.3 Student Activity:  Students observe a teacher demonstration to learn how to connect a voltmeter in a circuit correctly. Students use the voltmeter to take readings across the cell and light bulbs in the series and parallel circuits constructed in Activity 2.1 (see diagrams 3 and 4 in the Teacher Facilitation section below). They record readings, the location of their measurements (using schematic drawings and the symbol for a voltmeter), and their working definition of potential difference in their Science notebook. Students take part in a teacher-led discussion of potential difference. They then use their numerical values and any patterns they notice to write a general description of potential difference in series and parallel circuits.

Teacher Facilitation:  Students need advice on the following topics prior to the activity: how to take potential difference (voltage) readings across a circuit component; the symbol for a voltmeter; and, a working definition of potential difference. The bowling ball analogy described below has fewer limitations than a water analogy for explaining voltage or potential difference. Moving electrons represented by the bowling balls (electricity) have the potential to do work. That potential is lessened after the electrons have passed through a device represented by a water column (load). Voltmeters measure the difference in potential (i.e., potential difference) before and after electrons have passed through the device. The voltage measurement indicates the energy supplied by the source and dissipated by the load.

  

                                  Diagram 3                                                                   Diagram 4

 

2.4 Student Activity:  Each student group creates a circuit with a single ohmic resistor (not a light bulb) and a variable voltage supply as shown in the diagram below. Different groups use different resistors (e.g., 15, 20, and 30 ohms) and for five different voltages across the resistor they measure and record the current passing through the resistor. Students graph their own results (voltage on the vertical axis) and the results of two other groups that used two different resistors. They use the slope of the graphs to determine the resistance and derive the relationship between voltage, current and resistance (Ohm’s law).

Students work in groups to create a circuit with two ten-ohm resistors in series with a variable voltage supply. From voltage and current measurements they determine the resistance of the two resistors in series. They repeat this task using the two resistors connected in parallel. From these results, students compare the electrical resistance of their series and parallel circuits with that of a single resistor.

Diagram 5

Teacher Facilitation:  Review with students the calculation and interpretation of the slope of a graph - refer to Unit 1 and the Grade 9 Mathematics course. As an extension, teachers may use an ohmmeter and/or colour codes on the resistors to verify the resistance values determined from the slopes of the graphs.

2.5 Student Activity:  The students solve exercises on:

·         the relationship among potential difference, current, and resistance (V = IR)

·         the relationship among power, voltage, and current ( P = IV)

·         the relationship among energy, power, and elapsed time  (E = P/\t)

·         the cost of energy used

·         percent efficiency = (desirable energy output / total energy input ) ´ 100

Teacher Facilitation:  Ensure that correct SI units are used for the quantities addressed in the exercises. Prepare a worksheet or assign questions from a text for students to complete at home. The teacher may also perform a demonstration on efficiency to introduce concepts of energy input and output. A suitable demonstration would be to record the time required to heat a sample of water in a kettle of known power rating over a specified temperature range. Energy input is calculated using E(in) = Pt, and desirable output is calculated using E(out) = mass ´ temperature change ´ specific heat capacity.

2.6 Student Activity:  Students formulate a question about electricity within a circuit and restate it in a testable form. They plan on paper the circuit they intend to build in order to test their question. Once approved by the teacher, students carry out their experiment, record the results and present their findings.

Teacher Facilitation:  Monitor the questions students are attempting to ask to ensure that they can be reasonably and safely done. Monitoring of student work to ensure safety of students and equipment continues as investigations are conducted.

Some sample questions are:

·         What is the relationship among the number of dry cells connected in series or in parallel, the potential difference of the source, and the current that passes through a resistor?

·         What is the relationship between current and two different resistors connected in series and in parallel?

·         Does the light bulb behave like an ohmic resistor? Explain.

·         What potential difference and current are measured in a circuit composed of both parallel and series components?

Assessment/Evaluation Techniques

·         Use schematic diagrams to assess and evaluate understanding of concepts.

·         Use rubrics to assess skills in measuring and recording data.

·         Use a checklist to ensure appropriate and safe use of equipment.

·         Use answers to problem set to evaluate understanding of concepts.

·         Use a test to assess and evaluate understanding of concepts.

Accommodations

Refer to TSM - Accommodations for Students with Special Needs (page i - Phase 1)

Resources

Refer to Unit Resources.

A number of web sites that focus on rubrics are listed in the TSM for rubrics- Phase 1.

Teachers may find useful reference material for their own background in senior physics textbooks. Current student textbooks will also be helpful in this unit.

Demonstration versions of software packages of physics simulations, including electrical circuits, can be found at http://www.crocodile-clips.com/education/

 

Activity 3:  Electrical Energy Production

 

Time:  360 minutes

Description

This activity requires students to find and assess information regarding different methods used to generate electricity, e.g., tidal, hydro, wind, nuclear, solar, geothermal energy, fuel cells, biomass, and fossil fuels. The social, economic, and environmental costs and benefits related to these methods are compared.

Strand(s) and Expectations

Strand(s):  Physics

Expectations:  PH1.13, PH2.04, PH2.06, PH2.08, PH3.02.

Planning Notes

·         Prior to the research activity, co-ordinate with the teacher-librarian the time for students to conduct research either in the resource centre or using resource materials that have been brought to the science room. The research topics are the various energy resources that can be used for electricity production and the transformation of different forms of energy to electricity.

·         The Geography department may be a good source of information.

·         Videos or Internet sites are sources of information on forms of energy used in the production of electricity.

·         A field trip could be arranged for students to visit a generating station or tour the school with the custodian or board electrician to look at the electric system.

Prior Learning Required

Students should know that energy can be converted from one form to another. They should also be able to list various forms of energy (e.g., mechanical, heat, light, sound, electrical, etc.). Students should have the ability to initiate inquiry and research: to take notes from a variety of resources, organize the notes in a logical fashion, cite sources, and produce and edit drafts before the completion of the final report.

Teaching/Learning Strategies

3.1 Student Activity:  Students participate in a teacher-led discussion on energy production and transfer. They make notes on the topics as a starting point for research on the conversion of energy to electricity.

Teacher Facilitation: The teacher presents information on the generation of electricity from tides, hydro, wind, nuclear, heat via thermocouples, solar, geothermal, fuel cells, biomass, and fossil fuels. A graphic organizer may be useful to assist students in note making.

Questions to consider include:

·         What conversions have occurred?

·         Where is the energy available?

·         What are the costs?

·         What types of wastes are produced?

·         How does our dependence and consumption of electricity affect our environment?

·         What do all these methods of generating electricity have in common?

·         Are some forms more efficient than others? Why?

·         How might we alter our lifestyles to lessen the environmental impact of our energy use?

3.2 Student Activity:  Students work in groups to research information on various methods of generating electricity then present the information to the class in a form of their choice (e.g., video, live presentation, written report, etc.). Students make notes regarding information gathered from the presentations of other groups.

Teacher Facilitation:  Co-ordinate the research session with the librarian and monitor the quality and quantity of information retrieved and group dynamics.

3.3 Student Activity:  Students brainstorm in groups the criteria needed to compare two types of energy sources (e.g., dry cells and rechargeable cells). They use a graphic organizer to capture the discussion and display the results. Some criteria to discuss include the cost in producing and disposing of the cells, the environmental impact of production and disposal, ease of acquisition, energy available per unit cost, and life expectancy.

Teacher Facilitation:  Ensure that criteria for evaluating the alternatives are established, since those criteria will be used when the activity is extended to the evaluation of larger-scale energy production in Activity 3.4.  A teacher-directed discussion can be used to link 3.3 to 3.4.

3.4 Student Activity:  The students work in groups to evaluate the feasibility and efficiency in establishing a self-contained electrical energy system in Ontario. Some possible scenarios include: a town on the Missinnabi River, a cottage in North Bay, a house on Centre Island, a farm in Aurora, a small remote community, an urban office tower, or a crescent in a metropolitan neighbourhood. The intent is to determine whether it is feasible to create a self-sustaining environment (in energy terms) where electricity is not purchased commercially but is converted from an alternative source/form in this environment. In completing this activity students evaluate the situation using criteria such as those established in Activity 3.3.

After the group discussion, each student prepares a report summarizing the findings, evaluating the feasibility and suggesting a course of action for the particular situation.

Teacher Facilitation:  Suggest a variety of scenarios to be considered, such as those listed above. Moderate and guide the students in group discussions. It is necessary to define the expectations for this activity for students to help them put limits on the research that they do and to assist them in making decisions about feasibility and courses of action they might propose.

Some questions to start the inquiry might be:

·         Where does the electricity for the area come from now?

·         How much energy/electricity is needed in a day?

·         How much does it cost to supply electricity for a day?

·         What are some other forms of energy that could be converted to electricity?

·         Instead of purchasing electricity commercially, is it more feasible to obtain it by other methods?

·         What impact does this type of energy conversion have on the environment?

·         What is the capacity and the reliability of the alternative source?

3.5       Optional Student Activity:  A field trip to an electricity-generating station.

Assessment/Evaluation Techniques

·         Refer to TSM- Phase 1 - Rubric for Collaborative Group Work and TSM - Partial Rubric for Inquiry - Research to assess students research skills

·         Rubrics can be used to assess students’ presentation skills (Course Profiles: Geography).

·         Student notebooks can be reviewed to assess understanding of basic concepts. The Essential Science profile (http://www.curriculum.org) contains two appendices (OV-2 and OV-5) which are useful resources for this assessment /evaluation.

·         Refer to TSM- Phase 1- Marking Scale (rubric) for Written Report to evaluate written product.

Accommodations

·         Refer to TSM - Accommodations for Students with Special Needs (page i - Phase 1).

·         Ensure field trips planned can accommodate students with special needs (e.g., wheelchair accessible).

·         Teacher-prepared file-folders containing information on energy production may be used in class to supplement or replace library resources.

Resources

Refer to the main listing for the unit.

 

Activity 4:  Static Electricity

 

Time:  120 minutes

Description

The activity allows students to demonstrate their understanding of static electricity.

Strand(s) and Expectations

Strand(s):  Physics

Expectations:  PH1.01, PH1.02, PH1.03, PH2.09, PH2.10, PH3.01, PH3.03.

Planning Notes

Be aware of students with medical conditions (e.g., epilepsy or heart conditions), who should not participate in high-voltage demonstrations. Teachers should consult with those who are familiar with high-voltage equipment before using it. All electrical equipment must be CSA approved and checked to ensure that connections are tight and wiring is not damaged. Advise students at the outset how their notes, diagrams and reports are to be assessed in this activity.

 

Materials needed for this activity may include:

·         class set of electroscopes and accessories

·         Van de Graaff generator

·         Wimshurst machine

·         Tesla coil

·         Jacobs ladder

Prior Learning Required

Students were introduced to this topic in Activity 5 of Unit 1.

Teaching/Learning Strategies

4.1 Student Activity:  Students participate in a discussion/review of static electricity as covered in Activity 5, Unit 1. An alternative would be to ask students to prepare a concept map or do a graffiti exercise. The students observe demonstrations of static electricity generating devices (e.g., Van de Graaff generator, Tesla coil, Jacobs ladder, Wimshurst machine). Students make notes on the demonstrations as directed by the teacher.

Teacher Facilitation:  Review the two types of charges, the law of electrostatics, and the concept of neutrality and charge separation.

4.2 Student Activity:  Students charge an electroscope by conduction and induction and make a series of diagrams to indicate the flow of electrons in the two phenomena.

Teacher Facilitation:  Assist the students in developing an explanation of the charging of the electroscope. Relate the importance of static electricity to common devices (e.g., grounding in electrical devices, photocopiers and laser printers, industrial electrostatic precipitators, lightning rods, electrostatic air cleaners, and paint sprayers).

The teacher may extend this activity by having students attempt to discharge a charged electroscope using a variety of conductors and insulators. They may also have students attempt to charge a neutral electroscope that is surrounded by a grounded metal screen to simulate the purpose of shielded cables such as those in cable television.

Assessment/Evaluation Techniques

·         Use the graffiti exercise to assess students’ prior knowledge.

·         Develop a checklist to assess and evaluate student diagrams of conduction and induction.

Accommodations

·         Refer to safety notes at the beginning of this unit for usage of equipment with high voltages.

·         Substitute a teacher demonstration for class activity if there are not enough electroscopes for the whole class.

Resources

Refer to Unit Resources.

 

Activity 5:  Simple Home Circuits

 

Time:  180 minutes

Description

This activity allows for a review of the skills related to simple electric circuits and provides an opportunity to relate knowledge of electric circuits to applications in the home. Students use circuitry to relate electricity to common household wiring experiences (e.g., the use of dimmer switches in lighting, how simple fuses work in stoves and automobiles, the use of circuit breakers, the use of three-way and four-way switches in house lighting).

The activity allows students to see the relevance of electric circuitry without reference to examples that would require knowledge of electromagnetism, which is beyond the expectations of this course.

Strand(s) and Expectations

Strand(s):  Physics

Expectations:  PH2.01, PH2.02, PH2.03, PH3.01.

Planning Notes

Materials needed per group for this activity include:

·         12 wires with alligator leads

·         2 light bulbs (6 V) in sockets

·         6 V power source

·         1 lead pencil (longitudinally dissected ahead of time)

·         2 three-way switches (wood block with three nails)

·         1 four-way switch (wood block with four nails)

·         nichrome wire of various gauges

The teacher should prepare sets of equipment for simulating three and four-way switches using wooden blocks and nails as shown in the diagrams.

              

                  block with three nails                                            block with four nails

                   = three way switch                                                 = four way switch

When heating the nichrome wire, beware of burns to fingers and contact with flammable materials.

Prior Learning Required

Students should have some experience with wiring circuits with alligator leads and dry cells.

Teacher/Learning Strategies

5.1       Student Activity:  In small groups students observe the effect of a sliding resistor on the brightness of a light bulb. Students connect one terminal of the 6 V power source to one side of the light bulb. An alligator lead attached to the other side of the bulb is slowly rubbed along the exposed graphite core of a pencil which has been dissected longitudinally to remove half the wood. The other end of the pencil is connected by a lead back to the power source.

Students make comparisons between this activity and the dimmer switches found in homes or automobiles. In their Science notebooks, students use their knowledge from Activity 2 to explain their observations.

Teacher Facilitation:  Remind students of the work done in Activity 2 (if necessary), but avoid providing a complete explanation. As an extension, students could try pencils with a different type of core (e.g., coloured-pencil, various hardness, different thickness of graphite core). (Note that commercial dimmer switches are not simple variable resistors as this device is.)

5.2 Student Activity:  Students observe teacher demonstrations of the heating effect of an electric current on various gauges of nichrome wires. In their Science notebooks, students relate their observations to light bulbs, toasters and fuses. Students consider the danger of replacing fuses with those that have a higher current rating.

Teacher Facilitation:  Set up the demonstration using two binding posts (two nails partly embedded in a wooden block). Choose two gauges of nichrome wire, one to glow and one to burn through when electricity is applied. Caution the students against the possibility of burns from the hot wire. Explain the difference between fuses and circuit breakers as means of interrupting current flow. Demonstrate the operation of a circuit breaker using a bimetallic strip and a heat source. As an extension, the teacher can discuss the thermostat as a temperature sensitive switch.

5.3 Student Activity:  Students design and build a circuit using nails and wood three-way switches that allow one light bulb to be turned on or off from two different locations. Once successful, they draw schematic diagrams of the circuit. This could form the basis for further class discussion/construction of variations on the circuit (e.g., using two light bulbs, both on, both off, or one on, one off). Students write a brief description of how the three-way switch works and situations where this type of switch may be used.

Teacher Facilitation:  Display a model using commercially purchased three-way switches and a lamp/light bulb as an introduction to the activity. The technology department may be able to assist in building a model, and in newer schools, the classroom is likely equipped with three-way switches for controlling the lights.  It would be useful to model a standard two-way switch using the nails and wood as below to help students see how the alligator clips act as switches.

The diagram below is a guide to what the students should build:

Optional Student Activity:  Students who quickly complete Activity 5.3 may design and build a circuit using two three-way switches and one four-way switch (a block of wood with four nails) to turn a light on and off from three different locations. Students write a brief account of the usefulness of this circuitry (e.g., turning a garage light on or off from two locations in garage and one inside the house on cold winter nights).

Teacher Facilitation:  Use the diagrams below to offer suggestions as appropriate. You may wish to demonstrate the switching system to the entire class after sufficient time has been allotted for the activity.

5.4       Extension Student Activity:  As an extension, please refer to Activity 4 in the Applied Science electricity unit. Students link what they have learned about circuits to the wiring found in homes, and develop skills in wiring simple household circuits. Some options would be:

·         students perform the activity as described in the Applied Science course profile, Activity 4;

·         students participate in a workshop conducted by members from an Applied Science class;

·         students examine circuits constructed by students in Activity 4 of the Applied Science profile to identify the accepted principles and practices for residential wiring;

·         students select this as an option for the Culminating Task described in Activity 6.

Assessment / Evaluation Techniques

Review notebooks and schematic diagrams to assess and evaluate accuracy and understanding of concepts.

Accommodations

·         Refer to TSM - Accommodations for Students with Special Needs (TSM page i - Phase 1).

Resources

Refer to Unit Resources.

 

Activity 6:  Culminating Task

 

Time:  180 minutes

Description

Students brainstorm ideas for projects that they might design and construct to address a problem or challenge related to electricity or electronics. They use the skills and knowledge that they have acquired to define the problem and to describe a device that can provide a solution to it. Under the teachers direction they help to define the criteria by which the product should be assessed and evaluated, then draw a schematic diagram of their proposal, construct the device, and test it according to the criteria.

Strand(s) and Expectations

Strand(s):  Physics

Expectations:  PH2.01, PH2.03, PH2.04, PH2.06, PH3.01, PH3.03.

Prior Learning Required

The activity requires the skills and knowledge acquired through the unit.

Teaching/Learning Strategies

6.1 Student Activity:  Students participate in a brainstorming activity to identify an authentic challenge or problem that is related to electricity. The students help to identify criteria by which their design and construction are evaluated.

Teacher Facilitation:  Present several authentic problems and guide students to brainstorm solutions that involve their construction of electric or electronic devices. Facilitate a brainstorming session to identify other problems, challenges or extensions to previous work that would involve the construction of devices. A list of these may be maintained in the classroom on the Wonder Wall. Some suggested projects are a quiz game buzzer, a burglar alarm, the Kelvin water drop apparatus (see current science supply catalogues, or http://www.ph.unimelb.edu.au/lecdem/el7.htm), a temperature sensitive personal fan, an electric generator, or basic residential wiring.

6.2 Student Activity:  Students identify the problem, challenge, or extension on which they will work. They design a plan to solve the problem using only low voltage, obtain approval to proceed, complete the construction and test the product.

Teacher Facilitation:  All student projects must be operated at low voltage, using dry cells or a laboratory power supply operating at below 24 V. Monitor the complexity of each project to ensure that it is safe and neither too trivial nor too complicated to be accomplished in the allotted time with available materials. Be prepared to challenge the students who finish early to test their device under various conditions and offer possible modifications.

If students plan to use projects described in books, magazines or other sources, they must modify the project so that it becomes their own.

Assessment/Evaluation Techniques

Use a rubric or checklist to assess and evaluate the product in relation to the plan - modifications, corrections and changes. Refer to TSM Final Assessment Inquiry Rubric (p. xvi - Phase 1).

Accommodations

·         Refer to TSM - Accommodations for Students with Special Needs (TSM page i - Phase 1).

Resources

A variety of books containing electricity and electronics projects is listed in science supplier catalogues.

 

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