Course Profile   Science, Grade 9 applied, Public

 

Unit 4:  Physics: Electrical Applications

 

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

Time:  22 hours

Unit Description

The electricity unit begins with an examination of electricity as it relates to use in the classroom and at home. Sources of electricity are studied as well as the functioning of a variety of electrical appliances. Students build circuits using low voltage sources such as dry cells and power supplies but also consider how these model circuits relate to the wiring in their homes and/or in the school. The focus of this unit is to develop manipulative skills and skills related to design and construction.

Strand(s) and Expectations

Strand(s):  Physics

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

Specific Expectations:  PH1.01 to .07; PH2.01 to .09; PH3.01 to .05.

Activity Titles (Time and Sequence)

Activity 1

Survey of Electricity in the Science Classroom

120 minutes

Activity 2

Where Does Electricity Come From

300 minutes

Activity 3

Circuits

360 minutes

Activity 4

Home Electricity

300 minutes

Activity 5

Static Electricity

60 minutes

Activity 6

End-of-Unit Culminating Tasks

180 minutes

Prior Learning Required

Students have some background knowledge of circuitry from their Grade 6 Science and Technology classes. Until full implementation of the Grade 1-8 program, the amount of guidance, review and new teaching required in the activities changes from year to year. 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). Students have developed inquiry skills, for 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, demonstrations using concrete materials, diagrams, use of models, etc.).

Unit Planning Notes

Specific planning is described for each of the activities. However the following should be noted:

·         Static electricity demonstrations require dry conditions for excellent results; Activity 5 is best done in the dry winter months.

·         Access to a variety of resources is required for Activity 2 and Activity 6; co-ordinate with the teacher librarian ahead of time, either for class time in the centre, or for resources to be available in the science classroom.

·         It is necessary to arrange a guest speaker and/or book a video to provide information about careers related to electricity; the counselling department and/or co-operative education staff may be helpful.

·         Careers is a major focus in Unit 2 and is only briefly considered in this unit.

Some precautions on safety include the following:

·         Students must be 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.

·         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 in Crucible and links to other safety sites.

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.

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

Carousel activity; teacher-directed discussion

Students survey a variety of electrical devices, primarily those found in science rooms, and locate the main panel where electricity enters the school. They record their observations and current knowledge in a KWL chart which is completed during the unit. With teacher guidance they compare their findings to what would be found in their homes, cottages, farms, etc.

2

Inquiry research

Students locate and record information about the production and distribution of electrical energy in Canada with a focus on the variety of energy sources possible and the risks and benefits of each. They assess the bias which may accompany their information sources during their research. Products are shared with others in a class setting.

3

Equipment use and inquiry experimental

Students construct and draw schematic diagrams of simple electrical circuits and collect both qualitative and quantitative information about them. Voltage and current data are graphed and interpreted to confirm Ohms law. They solve simple Ohms law and efficiency exercises. They design and construct circuits to perform defined functions

4

Collaborative small group work; teacher demonstration; design and construct

Students link what they have learned about circuits to the wiring found in homes and apartments. They develop skills in wiring simple household circuit components. Issues of safety, the Ontario electrical code and related careers are referenced.

5

Teacher demonstration

Students observe and participate in demonstrations of a variety of static electricity devices and relate their behaviour to static charges in daily life.

6

End-of-unit tasks: note making, research, design and construct

Students summarize their learning in the unit on a KWL chart, research and report on the operation and construction of an electrical appliance and design and construct a low voltage circuit that solves an authentic problem.

 

Assessment/Evaluation

Activity

Assessing and Evaluating

Method or Instrument

1

Prior knowledge; group work; understanding of concepts

KWL chart; rubric for collaborative group work; rubric for declarative knowledge

2

Research skills; presentation; bias detection in resource materials

Rubric for inquiry-research; rubric in Geography profile for presentations; teacher evaluation of products

3

Understanding of concepts; measure and record data; use of equipment

Schematic diagrams; exercise answers; data charts and graphs in Science notebooks; test for content and safety

4

Understanding of concepts: construction of household circuits components; presentation of workshop

Performance assessment of workshop presentation; rubric for notebooks; checklist to evaluate wiring of circuits

5

Understanding of concepts; communication skills

Checklist to evaluate notes for communication skills; test for understanding of concepts

6

Understanding of concepts; presentation; KWL chart

Presentation rubric; rating scale for chart; product evaluation rubric

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:  Survey of Electricity in the Science Classroom

 

Time:  120 minutes

Description

This activity requires the students to make a survey of anything related to electricity found within the classroom. Students view the site of input of electricity to the school as well as various output devices found in the classroom. They relate the classroom survey to electricity in their home and in other types of structures. They use their survey as a starting point for asking questions which are recorded in their Science Journals and on the Wonder Wall for potential use in Activity 1.2 and in Unit 6 of the course.

Strand(s) and Expectations

Strand(s):  Physics

Expectations:  PH2.02, PH2.03.

Planning Notes

This activity requires careful setup ahead of time to ensure that students encounter a wide array of electricity-related items when completing their surveys. These may be organized in a series of stations with each station presenting a different item or they may be randomly arranged in the classroom in a more natural manner.

The following items could be included:

·         extension cords with different wire gauges;

·         items with three-prong plugs (e.g., microscopes, hotplates, centrifuges, light stroboscopes);

·         items with two-prong plugs of identical sizes (e.g., voltage adapters for portable stereos and calculators; older lamps and appliances);

·         items with two-prong plugs of different sizes (polarized plugs in newer lamps and appliances);

·         something that uses electricity from a battery or battery eliminator (e.g., portable pH meters, electronic scales, wrist watches, stop watches, laptop computers, computer interface devices);

·         devices with different energy transformations: electricity to light (microscopes, TV, grow lights), heat (hotplates, incubators), sound (tape players, TV/VCR), mechanical (centrifuges, aquarium pumps, wall clock);

·         a simple static demonstration (balloon stuck to a wall);

·         a picture of a lightning strike;

·         a calculator with a solar panel;

·         a circuit board from a computer or calculator;

·         a potato/lemon clock.

The examples mentioned do not include specialized receptacles and plugs associated with 220 V service (for clothes dryers, ranges, etc.). Questions related to these devices may be placed on the Wonder Wall, but are beyond the scope of this unit.

Prior Learning Required

No specific knowledge of electricity is required for the completion of this activity. One of the intents of this activity is to assess students’ prior knowledge of electricity.

Teaching/Learning Strategies

1.1 Student Activity:  Students do a survey of electricity items in their classroom. The survey is completed in their Science notebooks and includes a chart showing the components of the items and a list of the characteristics the items have in common. The survey is used to develop KWL charts in Activity 1.2. The completion of the charts is part of the end-of-unit task.

Teacher Facilitation:  Set up the classroom ahead of time to ensure that a large number of items is available for the survey. Enlist the help of a custodian to locate the circuit breakers or fuses for the classroom and include this as part of the survey. Similarly, find the location of the electrical feed into the school and show it to the students for inclusion in the survey.

Introduce the three parts of the end-of-unit task (Activity 6) completion of the KWL chart to be started in Activity 1.2, research on an electrical appliance, and a circuit construction.  Encourage them to begin planning early for this activity.

1.2 Student Activity:  Students begin their KWL charts by recording what they already know (K) about electricity and questions to which they want (W) answers. They record what they have learned (L) as they proceed through the unit. Questions from their KWL chart may also be recorded on the Wonder Wall.

Teacher Facilitation:  Describe the requirements of a KWL chart to the class and ensure that the students are aware that this is part of their end-of-unit task. An alternative activity would be to use a mind or concept map and have students update/redo theirs at the end of the unit, again as part of the end-of-unit task.

1.3       Student Activity:  Students participate in a teacher-led discussion focussing on the similarities and differences between electricity use in the classroom and electricity use in the home. Students discuss how wiring and electrical components have changed over time. From any experiences with cottages, homes or farms of different ages, students share information on alternative wiring and electrical components in structures (e.g., the use of porcelain insulators and separate single wire installations in very old structures).

Teacher Facilitation:  Pose questions to the class and ensure that all students have a chance for input. Note that some students, for example those living in apartment buildings, may not be able to collect the information necessary to answer many of the questions below and may not have had opportunities to see alternative electrical wiring or components. Photographs and other illustrations may be useful alternatives. Assign these questions for homework prior to discussion to allow students a chance to do a quick home survey.

Some questions include:

·         Does your home/apartment use fuses or circuit breakers in the main panel box?

·         Is there more than one panel box in the home? Where are they located? How are they different from each other?

·         What is the current rating (amperage) of your home service? (Written on newer electric meters. Common services are 100 A or 200 A.)

·         Where are the electric meters located (homes and school)?

·         Are ranges and dryers directly wired or plugged into the circuit?

·         What styles of outlets are in your home/apartment? (two vs. three-prongs)

·         Do you have special receptacles in the bathrooms or outside your home /apartment? (GFI - Ground Fault Interrupters)

·         Is the wiring different in a barn, a cottage, or a very old house? In what ways?

·         Introduce the concept of a black box and point out that a number of the devices surveyed involve black boxes, such as the wiring behind walls, in switches and receptacles, and in appliances.

Assessment/Evaluation Techniques

·         Use the partially completed KWL charts to assess students’ prior knowledge (but return them to the students for completion through the unit).

·         Students’ participation in the CSGL exercise can be formatively assessed by teacher and/or students using the rubric for collaborative group work (TSM page x - Phase 1) and the Achievement Chart for Science.

·         Use direct communication with students to assess their understanding of concepts and participation.

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 Tasks. U.S.A: ASCD Publishers, 1998. ISBN 087120-339-1.

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

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

 

Activity 2:  Where Does Electricity Come From

 

Time:  300 minutes

Description

In this activity students focus on the production of electricity currently used in Ontario and the rest of Canada as well as some alternative methods of production. Students research information in the library/resource centre from text and/or electronic sources. Their research focuses on the production process, the risks and benefits associated with each method, and the feasibility for use in their community. Students should be made aware of bias inherent in some resources, especially those published by individuals or groups who are stakeholders in particular energy enterprises or who hold strong views about different production and distribution methods.

Strand(s) and Expectations

Strand(s):  Physics

Expectations:  PH2.05, PH2.06, PH2.07, PH3.03, PH3.05.

Planning Notes

If this unit is sequenced later in the course, it can be assumed that students have had several opportunities to practise the skills involved in this activity. Formal lessons may only be beneficial to students who have experienced difficulty with prior tasks of this nature.

Prior Learning Required

Students need to 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). 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

2.1 Student Activity:  As a class, students brainstorm a list of different energy producing technologies: fossil fuel, nuclear, hydroelectric, wind, biomass, geothermal, tidal, fuel cell, photovoltaic.

Teacher Facilitation:  Ensure that the students develop as large a list as possible as this provides the topics for upcoming activities. A video or textbook reading assignment might help with this activity. As well, explain how most of these methods involve the use of generators to produce the electricity with turbines powered by moving wind, water or steam. It is likely necessary to include a discussion of electricity distribution through the grid in the province of Ontario. (Check the Resources list at the beginning of this unit for some sources of information.)

2.2 Student Activity:  Prior to beginning their research, students should complete a bias detection exercise where they compare the information presented on the same topic from two points of view.

Teacher Facilitation:  Refer to Teacher Support Materials (TSM)- Phase 1 - Bias Assessment and TSM - Questions. The teacher should select the two pieces of information to be assessed and develop a series of questions. The activity can take place in a class discussion, as an individual reflection, or some combination of both. One suggestion is to read two short articles (e.g., nuclear safety published by the nuclear industry and one from an anti-nuclear interest group) and to discuss bias in each. 

2.3 Student Activity:  Each student group completes research on the energy source selected/assigned and reports findings to the class. The research focuses on the production process, risks and benefits associated with each method and the feasibility for use in their own community.

Teacher Facilitation:  Arrange for class time in the resource centre/library, or provide a variety of resources in the classroom and monitor student progress as they work.

2.4 Student Activity:  Students watch a video or a presentation describing employment opportunities available in the fields of energy production and distribution.

Teacher Facilitation:  Enlist the assistance of the counselling department or a teacher with co-operative education contacts to locate a guest speaker, or locate a suitable video resource as an alternative. This activity may be combined with Activity 4.7 or may be omitted entirely provided that Activity 4.7 is completed to meet Expectation PH3.05.

Assessment/Evaluation Techniques

·         Refer to TSM Phase 1 - Partial Rubric for Inquiry - Research to assess and evaluate research skills.

·         Refer to the rubric in the Geography course profile to assess and evaluate presentation skills.

·         Refer to TSM Phase 1 - Bias Assessment and TSM Questions.

Accommodations

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

Resources

See Unit Resources.

A variety of Public Interest Research Groups operate throughout Canada. Searching for Canadian locations through the search engine at http://www.canada.com/home.asp?page=fullsearch locates them.

Environmental interest groups include the Sierra Club and Greenpeace. Local chapters can be located through Internet web searches.

 

Activity 3:  Circuits

 

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, 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:  PH1.03, PH1.04, PH1.05, PH1.06, PH1.07, PH2.01, PH2.04, PH2.08, PH2.09.

Planning Notes

Make sure, prior to beginning the series of activities, that the required equipment is available. Materials required for the activities include:

·         wires

·         light bulbs

·         alligator leads

·         6 V dry cells

·         variable power pack

·         ammeters and voltmeters

·         ohmic resistors (of different resistance)

·         graph paper

·         teacher-prepared problems or a series of problems selected from 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. Eventually all students have experienced this, but for the first few years, this may be less true. Consequently, the amount of guidance, review and new teaching required in the activities changes from year to year.

Prior to beginning the unit, the teacher should have experience in constructing series and parallel circuits, and in correctly using ammeters, voltmeters, and ohmmeters.

Prior Learning Required:

·         Refer to TSM - The Ontario Curriculum, Grades 1-8 Science and Technology (TSM pages xix - xxi - Phase 1) for a brief summary of what has been addressed in earlier years. Students using The Ontario Curriculum: Grades 1-8 have had experience building series and parallel circuits in Grade 6.

·         Students have experience both in Grades 1-8 and in the Grade 9 Mathematics program with creating graphs from data and interpreting the meaning of graphs involving two variables. (Refer to Unit 1 of the Grade 9 Mathematics profile.)

Teaching/Learning Strategies

3.1 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 share their constructed circuits with the class. Model circuits (series and parallel) are selected as examples for Activities 3.2 and 3.3. Students then make notes, record definitions and/or examples of the following: source, load, series circuit, parallel circuit, current, characteristics of schematic drawings and the meaning of a variety of common schematic symbols.

Teacher Facilitation:  Remind students of some of the past work they may have done building electrical 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 or blackboard drawings) help students to make their own notes 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 power source and light) as the accepted way of representing circuits.

3.2 Student Activity:  Through teacher demonstration, the students have learned how to correctly connect an ammeter into a circuit and to perform a touch test to ensure safety of equipment prior to taking a measurement. The students then use the ammeter to take readings at specific locations in the series and parallel circuits constructed in Activity 3.1. Challenged to explain what it is they have been measuring, the students take part in a teacher-led discussion of electrical current. They record their readings, the location of their measurements (using schematic drawings and the symbol for ammeter) and their own working definition of electric current in their Science Journal. They use their numerical values 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 the ammeter in series in a circuit and then performing a touch test (Before the last alligator clip is firmly attached, it is briefly touched to see whether 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 the diagram below. This procedure is then repeated with the parallel circuit, with readings taken at the locations shown in the second diagram. Note: Only one reading is taken at a time; the ammeter is then moved to the next location.

 

                                                Diagram 1                                       Diagram 2

The flow of water may be useful as an analogy for electricity in circuits, although it has limitations (as do all analogies) and will be abandoned when work is done on voltage. One reference for the water analogy is http://http.cs.berkeley.edu/~randy/Courses/CS39C.S97/telegraph/electricity.html.  Many secondary school physics textbooks also address this analogy.

3.3 Student Activity:  Through teacher-demonstration the students learn how to correctly connect a voltmeter. The 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 their readings, the location of their measurements (using schematic drawings and the symbol for voltmeter) in their notebooks, and their working definition of potential difference in their Science Journals. Students take part in a teacher-led discussion of potential difference (see Teacher Facilitation). They use their numerical values and any patterns they notice to write a general description of potential difference in series and parallel circuits in their Journals.

Teacher Facilitation:  The following topics need to be dealt with prior to laboratory work: how to take voltage readings across an object (including a touch test); the symbol for voltmeter and a working definition of potential difference using a bowling ball analogy (shown below). The water analogy is extremely limited in explaining voltage or potential difference. It may be best to state that moving electrons represented by the balls (electricity) have the potential to do work. That potential is lessened after the electrons have passed through a device represented by the water column (load). Voltmeters measure the difference in potential (i.e., potential difference) before and after electrons have passed through the device. It may be best to state that the voltage measurement indicates the energy supplied by the source and dissipated by the load.

  

                                 Diagram 3                                                                    Diagram 4

 

3.4 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. They graph their own results 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 among voltage, current, and resistance (Ohm’s law).

Diagram 5

Teacher Facilitation:  Review the calculation and interpretation of the slope of a graph - refer to Unit 1 and the Grade 9 Mathematics course. As an extension, an ohmmeter and/or the colour codes on the resistors could be used to verify the resistances determined from the slopes of the graphs.

3.5       Student Activity:  Students work in small groups to build circuits powered by dry cells (up to 6 V) to perform specific functions determined by the teacher. These devices may include switches, buzzers, motors, bulbs, and LEDs. The students should design the circuit diagram and have it approved for safety (of both themselves and the equipment) by the teacher before building it.

Teacher Facilitation:  Students are to be told the functions to be performed by the circuit designs. Any number of switches can be used along with a variety of devices. Check the schematic diagrams designed by the students to prevent damage to the student or the equipment. Also check that the power source is appropriate for the device being used. Examples of such devices are:

·         three light bulbs, two with the same brightness, and one different

·         three devices (bulbs, motors, or buzzers), any two devices operating at one time

·         three devices, one device is permanently on and the other devices can each be turned on/off

·         two cells and a single bulb where the bulb is as bright as it was in a circuit with one cell

·         three devices, two devices can be turned on/off together and the other device can be turned on/off independently

The teacher may wish to assign more than one challenge to each group depending upon the time available.

3.6 Student Activity:  The students solve exercises related to:

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

·         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 some 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) = P ´ t, and desirable output is calculated using E(out) = mass ´ temperature change ´ specific heat capacity.

Depending on the time available and interest of the students, the teacher may extend this activity by considering the relationship among power, voltage and current (P = IV); energy, power and elapsed time (E = Dt); and how the cost of household electrical energy is calculated. These topics are found in the Academic Profile of this course.

Assessment/Evaluation Techniques

·         Use a checklist on student schematic diagrams to assess and evaluate understanding of concepts.

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

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

·         Use an exercise 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 (TSM page i - Phase 1).

Resources

Refer to Unit Resources.

Teachers may find useful reference material for their own background in physics textbooks written for senior students. Current student textbooks are helpful in this activity.

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

 

Activity 4:  Home Electricity

 

Time:  200 minutes

Description

In this activity, students link what they have learned about circuits from Activity 3 to the wiring found in homes. Students also develop skills in wiring simple household circuit components. Issues of safety and the Ontario electrical code are referenced. A classroom visit by an electrician or electrical inspector from Ontario Hydro can provide more insight into electrical production, distribution, installation and related careers.

Strand(s) and Expectations

Strand(s):  Physics

Expectations:  PH2.01, PH2.04, PH2.08, PH3.01, PH3.05

Planning Notes

·         Although this is an introductory activity, the teacher needs to become somewhat familiar with home wiring techniques prior to this activity. A member of the technology department can provide assistance. Do it Yourself books also provide step-by-step instructions for home wiring. Student-wired circuits should not be plugged into the wall outlets.

·         In order to complete this activity, the following materials are required for each group:

·         3 outlet/switch boxes;

·         2 octagon junction boxes;

·         1 switch;

·         2 receptacles;

·         1 lamp base;

·         approximately 3 metres of 14/2 cable, cut in 0.5 metre lengths;

·         Marrettes (size 33);

·         needle nose pliers;

·         wire stripper/cutter;

·         hobby knife;

·         red-handled Robertson screwdriver.

·         Each class should have its own set of materials (tools not included) so that the circuits constructed by the groups can stay intact between classes. This material can be used year after year although the cable may have to be replaced periodically because it becomes damaged through repeated use. All the equipment is readily available at hardware stores and building supply outlets. Buy the cheapest that is available (buying in packages of 10 may net more savings). Obtaining them through the Board maintenance/custodial department may be another alternative. The tools can be borrowed from the technology department of your school.

Prior Learning Required

The students need to know the characteristics of parallel and series circuits and the role of switches in stopping the current in a circuit.

Teaching/Learning Strategies

4.1       Student Activity:  The students review the characteristics of parallel and series circuits from their previous activity and predict the type of circuits found in the home. They examine a 40 to 50 cm length of 14/2 cable by using the hobby knife to remove approximately 12 cm of the white plastic insulation from each end of the wire. Students discover three wires inside: black or hot wire, white or neutral wire and bare copper or ground wire. Through discussion, students learn the functions of these three wires and then record information in their Science notebooks.

Teacher Facilitation:  The teacher directs the discussion to ensure that students understand that the components of a household circuit are connected in parallel circuit (equal voltage to each, other components continue to function even with one component not functioning) and that switches are connected in series. The teacher must review the safe use of x-acto knives prior to having students remove the insulation. The teacher may wish to do this ahead of time instead of having the students perform this task. The black wire carries the currents (with more potential - high voltage) from the source and the white wire returns the current. Both carry current and both are dangerous in spite of their names. The ground wire is a safety feature to neutralize charged objects and prevent shocks.

4.2 Student Activity:  The students, working in small groups, connect three cables together inside an octagon junction box. Three holes are opened in the junction box by popping out the slugs. One cable represents the feed into the circuit and the other two will be used in later parts of this activity. The ends of the wires are stripped (about 2 cm) using the wire strippers. All three black wires are connected using a Marette and all three white wires are connected in the same way. The ground wires are connected to the screw on the wall of the octagon box. The students describe the procedure for connecting wires in their Science notebooks.

Teacher Facilitation:  The teacher demonstrates the technique of wire stripping and connecting to the class and moves around the classroom offering assistance and advice. The teacher may discover a wiring expert in the class (such as a senior student in the technology area or a member of the school stage crew) and enlist this person for peer assistance. It is important to remember that screws tighten clockwise so that ends of wire attached to a screw must have a loop that is clockwise as well. The teacher should ensure that all group members are developing skills and not leaving the responsibility to one person. According to the electrical code, junction boxes must be accessible at all times and are not covered by any other building material.

4.3       Student Activity:  The students, working in small groups, connect two receptacles (with boxes) to one of the cables coming from the junction box. One receptacle is connected first and then the second is connected to the first using an additional piece of cable. The students describe the procedure for wiring receptacles in the Science Notebooks.

Teacher Facilitation:  The teacher reviews how to connect wires to screws (loops are in a clockwise direction to match the tightening of the screw) and draws the students attention to the different coloured screws on the receptacle - silver, brass, and sometimes green (near one end of the receptacle). White wires connect to the silver screws, black wires connect to the brass screws and ground wires connect to the green screw before connecting to the back of the box. Through discussion, the teacher relates plug shape to receptacle design: the larger prong on polarized plugs and receptacles matches the white (neutral) wire. If receptacles are wired correctly, the receptacles and the appliances that are plugged into them are grounded and will not shock the user.

4.4       Student Activity:  The students, working in small groups, connect a switch and lamp socket to the other cable coming from their junction box. An additional piece of cable is needed. The switch is connected first, two black wires on the switch, two white wires connected by a Marrette, and ground wires to the back of the box. The lamp socket is then wired, white to silver screw, black to brass and ground to receptacle box. The students describe the wiring of a switch and lamp socket in the Science notebooks.

Teacher Facilitation:  The teacher reviews how to connect wires to screws, the colour coding of screws and wires, and how to connect wires with Marrettes. The teacher draws the students attention to the two brass screws on the switch and asks them to predict how the switch are wired (in series, with the black wires). This is necessary so that the switch opens and closes the circuit on the hot, high voltage side. Switches are in the hot (black) wire so that when turned off, there is no voltage to the appliance. Lamp sockets are wired such that the threaded receptacle connects to the neutral (white) wire to reduce shock hazard when changing the light bulb if the switch is not turned off. Again the importance of correct wiring as a means of preventing shocks is stressed.

4.5       Student Activity:  Through class discussion, students and their teachers, develop a checklist for evaluating the wiring completed in Activities 4.2, 4.3 and 4.4. The students then employ this checklist to evaluate the work performed by their own group and to make any necessary revisions. Once this has been completed, one group’s work is evaluated by a second.

Teacher Facilitation:  The teacher ensures that the checklist established is comprehensive enough to provide useful feedback to the students. Items on the checklist may include: correct wires joined together; wires joined together tightly so that they don’t fall out of the Marrette; correctly coloured wires on screws; wires connected to screws correctly; etc. The teacher may assign evaluators to particular groups.

4.6 Extension Student Activity:  Students conduct a workshop for students in the Academic Science program in which they display their household circuits and explain the accepted principles and practices for residential wiring.

Teacher Facilitation:  Refer to the Academic profile, Activity 5.4 for a number of extensions to that program that involve the work done in the Applied course. If these options are not used, have the students dismantle the wiring that they have done in Activities 4.2 to 4.4.

4.7 Student Activity:  Students watch a video or listen to a presentation describing employment opportunities available as electricians.

Teacher Facilitation:  The teacher, with assistance of the counselling department, arranges for a video and/or guest speaker. This activity may be combined with Activity 2.4 or omitted entirely provided that Activity 2.4 is completed to meet expectation PH3.05.

Assessment/Evaluation Techniques

·         Use performance assessment of students preparation and delivery of a workshop on residential wiring to students in Academic classes (extension Activity 4.6).

·         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.

·         Use checklist to evaluate circuits.

Accommodations

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

Resources

Do-It-Yourself Home repair guides published by organizations such as Time-Life, Popular Science, Readers Digest and others are good sources of reference material.

Electrical Code Simplified - Residential Wiring Ontario Book 1. ISBN 0-920312-12-8 is a more detailed reference.

 

Activity 5:  Static Electricity

 

Time:  60 minutes

Description

This activity allows students to demonstrate their understanding of static electricity and its occurrence in daily life.

Strand(s) and Expectations

Strand(s):  Physics

Expectations:  PH1.01, PH1.02.

Planning Notes

Be aware of students with medical conditions (e.g., epilepsy, heart conditions) as they should not participate in high-voltage static demonstrations. Teachers should familiarize themselves with the equipment before using it in class demonstrations. Be sure to consult teachers with experience in the use of these devices. There are safety concerns related to potential eye damage, arcing to zipper, belt buckles, jewelry, etc. All electrical equipment must be CSA approved and periodically inspected for frayed wires, worn belts and loose connections.

Equipment needed for this activity includes:

·         Van de Graaff generator;

·         Tesla coil;

·         Wimshurst machine;

·         Jacobs ladder.

Prior Learning Required

Students were introduced to static electricity in Unit 1, Activity 5.

Teaching/Learning Strategies

5.1 Student Activity:  Students participate in a discussion/review of static electricity. A graffiti exercise or concept map would be an alternative exercise. The students observe demonstrations of static electricity generating devices and make notes on the demonstrations in their Science Notebooks. Students discuss common examples of static electricity and add information to their notes.

Teacher Facilitation:  Review types of charges, the law of electrostatics, and the concept of neutrality and charge separation. This material was addressed in Unit 1, Weird Water. Perform the demonstrations and allow students to participate after reviewing safety concerns. Relate the importance of static electricity to common devices and phenomena (e.g., lightning rods, static straps in automobiles, electrostatic spray painters, balloons sticking to walls, static cling in clothes and in clothes dryers and static attraction between brush and hair.) Details of the use of a graffiti chart are described in the Academic Science profile, Unit 5, Astronomy, immediately following Activity 1.2.

Assessment/Evaluation Techniques

·         Use checklist or rating scale to assess and evaluate student notes for communication skills - completeness, organization, and ease in understanding.

·         Use quiz to assess and evaluate understanding of concepts.

Accommodations

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

Resources

“Painting with Powder”, Toronto Star, Saturday July 10, 1999, p. J4 Information provided by Associated Powder Coating Systems: Powder Coating Institute; Wagner Powder System.

“Lightning, Natures High Voltage Spectacle”, National Geographic Volume 184 Number 1, July 1993.

 

Activity 6:  Culminating Tasks

 

Time:  220 minutes

Description

Each student should complete a KWL chart that was started in Activity 1, a descriptive report that explains how a particular appliance transforms electricity into another energy form (or forms), and the construction of a circuit that performs a particular task. This circuit may be low voltage or a household circuit. The low voltage circuit should be made operational; household circuits must not be connected to a source.

Strand(s) and Specific Expectations

Strand(s):  Physics

Expectations:  PH2.01, PH2.02, PH2.04, PH2.05, PH2.06, PH2.07, PH2.08, PH3.01, PH3.02, PH3.04.

Planning Notes

·         These activities were introduced to the students during Activity 1. Students should be reminded to keep their KWL chart up to date throughout the unit. Library/resource centre time should be booked prior to the end of the unit to allow students to get started on their research on the functioning of the different appliances.

·         There are many designs of electric devices available in texts and on the Internet. Students may use one of these as a starting point but need to make modifications to make the design and subsequent construction their own. Most class time in this activity is allotted to Activity 6.3.

Prior Learning Required

Students have gained experience in drawing schematics, constructing circuits, and in researching throughout this unit. These tasks allow the students to apply the knowledge learned and the skills practised in completion of three individual tasks.

Teacher/Learning Strategies

6.1 Student Activity:  The students complete the KWL Chart started in Activity 1 by filling in the final L column.

Teacher Facilitation:  Throughout the unit, periodically remind students of this assignment.

6.2 Student Activity:  The students individually research the operation of a particular appliance, explaining the energy conversions that occur. The presentation may be predominately visual but should be accompanied by some written explanations.

Teacher Facilitation:  Arrange for class time in the resource centre/library, or provide a variety of resources in the classroom, and monitor student progress as they work.

6.3 Student Activity:  The students construct a low voltage operational circuit or household, non-operational circuit that solves an authentic problem. Designs must be approved by the teacher before construction begins. Construction takes place during class time but equipment and material can be brought from home to supplement what is available to class. Students describe their products to the class during a Show and Share session.

Teacher Facilitation:  Assist students in choosing suitable authentic problems. Students could be directed to the Wonder Wall for ideas. Possible low voltage designs are burglar alarms, motion sensors, quiz game show buzzers, etc. Possible household circuit designs include a switching system which turns lights on and off from two or three different locations; two or more lights on the same circuit with their own switches; a light controlled by a switch and a separate receptacle on the same circuit; kitchen or bathroom installations, etc. For more information on switches, teachers may wish to refer to Activity 5, Academic. Under no circumstances should household circuit designs be tested with anything more than 24 V.

Assessment/Evaluation Techniques

·         Use rating scale/rubric to assess and evaluate KWL chart.

·         Use TSM- Phase 1 - Presentation Rubric to assess and evaluate Appliance presentation.

·         Use TSM- Phase 1 - Final Assessment Inquiry rubric to assess and evaluate the wiring project.

Accommodations

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

Resources

Web Sites

www.badscience.com

www.howstuffworks.com

 

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