PHYSICS

Stage 6

 

Preliminary Course

8.3 ELECTRICAL ENERGY IN THE HOME

This resource was developed as part of the Master of Teaching degree at the University of Sydney by Emman Choukair, Cristina del Vale and Cao Tran.

 

Any feedback to Ian Cooper, School of Physics, University of Sydney would be appreciated.

cooper@physics.usyd.edu.au

 

RESOURCES

 

WEB

http://www.energy.co.au/savesafe/athome.html

 

CONTENT SEQUENCE

Syllabus reference 8.3.1

·        Discuss how the main sources of domestic power have changed over time.

·        Assess some of the impacts of changes in, and increased access to, sources of power for a community.

·        Discuss some of the ways in which electricity can be provided in remote locations.

Syllabus reference 8.3.2

·        Describe the behavior of electrostatic charges, induction, positive, negative charges.

·        Define unit of electric charge as coulomb.

·        Describe electric field E = F / q

·        Recall use of the terms current, voltage and resistance.

·        DC and AC current.

·        Discuss how voltage varies around a circuit .

·        R = V/I

·        Explain qualitatively and quantitatively that resistance is related to potential difference.

·        Describe the difference between conductors and insulators .

·        Discuss qualitatively how : length, cross sectional area, temperature and material will affect the movement of electricity through a conductor.

Syllabus reference 8.3.3

·        Recall the terms, series and parallel circuits.

·        Explain why ammeters and voltmeters are connected differently in a circuit.

·        Discuss the distinction between series and parallel circuits in terms of the flow of the current.

·        Compare parallel and series circuits in terms of voltage across components and the current through them.

·        Explain why there are different circuits for lighting, heating and other appliances.

Syllabus reference 8.3.4

·        Explain that power is related to the rate at which energy is transformed from one form to another.

·        Describe the relationship between power dissipated, potential difference and current.

·        Explain that the total amount of energy depends on the length of time the current is flowing and can be calculated using: Energy = VIt and Power = VI

·        Explain why the kilowatt-hour is used to measure domestic electricity consumption instead of the joule.

·        Assess the advantages and disadvantages of labeling goods with power rating.

·        Explain why a simple scale has been used for energy rating on commercial goods and how these scales relate to potential difference and current.

Syllabus reference 8.3.5

·        Describe the behavior of the magnetic poles when they are brought close together.

·        Define the direction of the magnetic field at a point as the direction of force on a very small magnetic pole when placed at that point.

·        Describe the magnetic field around single magnetic poles and pairs of magnetic poles.

·        Describe the production of a magnetic field by an electric current in a straight current-carrying conductor and describe how the right hand grip can determine the direction of current and field lines .

·        Compare the nature and generation of magnetic fields by solenoids and a bar magnet.

·        Assess the impact of magnetic fields on society.

·        Discuss the effects of an electric shock from both a 240 volt AC mains supply and various DC voltages, from appliances, on the muscles of the body.

·        Identify the functions of circuit breakers, fuses and other safety devices in the home.

·        Outline the role of insulators in household appliances.

 

ACTIVITIES

·        Internet.

·        Electric field patterns.

·        Charge on the electron from copper plating experiment.

·        Students to show in two groups how DC & AC current works with them being the electrons.

·        Ebonite and perspex rods, pith balls.

·        van de graaff.

·        Plan and construct a experiment to show how V is related to I. Also to plan an investigation on how voltage varies around a circuit.

·        Get them to bring in different items which they think are conductors or insulators. You can then test them.

·        You could perhaps demonstrate this by using straws. Big straws, little straws and long straws. How much water (or alcohol) can you drink up.

·        Demonstration and practice on how ammeters and voltmeters are connected.

·        Can use role play with students and smarties showing what the ammeter and voltmeter measure (refer to engaging physics pg 102 - 103).

·        Experiment connecting series and parallel circuits and measuring current using ammeter.

·        Independent task, choose equipment to measure current and voltage in series and parallel circuits.

·        Observe diagrams and models of circuits for different purposes in the home ( Can use christmas lights to show why series circuits are not used for lighting in the home).

·        Design a model for circuits in the home on paper and on a circuit board (using light bulbs and switches).

·        Experiment measuring potential difference (voltage using voltmeter), current (I, using ammeter) of circuits and determine power dissipated and energy used using equations P = VI and E = VIt

·        Solve problems based on everyday uses of electricity, using power and energy equations and kilowatt-hour as units instead of joule when referring to domestic electricity consumption.

·        Gather information on energy ratings of different home appliances.

·        Define what a magnet is - show magnet.

·        Give different types of magnetism.

·        Discuss and show magnetic fields using magnet and iron fillings.

·        Hands on experience with two magnets to demonstrate repulsion and attraction of magnets.

·        Oersted’s experiment, intro. on what Oersted did when he did the experiment.

·        Define solenoid - show them one.

·        Set up a solenoid in a circuit so that they experience repulsion and attraction to a bar magnet (only 1 set of equipment).

·        Discuss electrocution/electric shock (ventricular fibrillation, brief).

·        Outline safety devices used to prevent electrocution and fires by electrical faults (setting up circuits in parallel).

·        Set up an experiment using a circuit containing a fuse so that the fuse melts when excess current passes through it.

·        Bring in electrical cord that has been cut in cross-section to show insulation.

·        Using diagrams, explain 3 wires in power point.

·        Asses the effect of different voltages on the muscles of the body (secondary info., data on heart).

·        Research how a defibrillator works using electricity to resuscitate the heart.

 

CONTEXT / PRESCRIBED FOCUS AREA

·        History of Electricity.

·        Electricity in the Home.

·        Applications of Technology.

 

ASSESSMENT

·        Poster.

·        Report based on experiment showing method used and results showing a clear understanding of what current and voltage are.

·        Assess their model circuits with a small explanation on the theory behind their design (small groups).

·        Assignment looking at power ratings of appliances in their homes, calculate how much energy is used by all these appliances if they were used for a certain period of time ( eg. 1 day) and with a given price (for 1 kWh) determine the cost for using each appliance and possible strategies to reduce consumption.

·        Exam, questions to work out F, B or V (right hand rule).

·        Design an experiment to lift a specified weight by designing an electromagnet.

·        Research and hand in 2 page summary on how magnets work in one of the following: pest control- by eg. use -of internet, telephone or stereo - speakers, magnetic tape.

 

Ian Cooper
School of Physics
University of Sydney

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