8.3 Electrical Energy in the Home

Richard Newbury
School of Physics - UNSW, 
November 1999.

 

1. Society has become increasingly dependent on electricity over the last 200 years

2. One of the main advantages of electricity is that it can be moved with comparative ease from one place to another through electric circuits

3. Series and parallel circuits serve different purposes in households

4. The amount of energy transformed in an appliance is related to the power rating of an appliance and the length of time it is used

5. Electric currents also produce magnetic fields and these fields are used in different technologies in the home

 

1. Society has become increasingly dependent on electricity over the last 200 years

  • 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

• Skills

analyse secondary information about one of the debates that took place to develop our current understanding about electricity from one the following:

  • p Volta and Galvani and their debate over animal and chemical electricity
  • p Faraday
  • p Ohm

• Useful Sites

Many good pages with historical perspective:

(these sites discuss ‘leaking electricity’ and address power consumption and ways in which it can be reduced.)

 

• Simple Demonstrations/Class Experiments

Construct series of ‘Volta cells’ using plastic cups, zinc & copper sheet, lemon juice electrolyte — can light a red LED with a few of these in series!

 

2. One of the main advantages of electricity is that it can be moved with comparative ease from one place to another through electric circuits

  • discuss qualitatively how each of the following affects the movement of electricity through a conductor:
    • p length
    • p cross-sectional area
    • p temperature
    • p material

• Skills

present diagrammatic information to describe the electric field strength and direction of

  • p a single charged object
  • p parallel plates
  • p a positive and negative charge

•Useful Sites

A good starting point is

 

3. Series and parallel circuits serve different purposes in households

  • explain why there are different circuits for lighting, heating and other appliances in a house

 

• Skills

construct model household circuits using electrical components

 

• Problem

Actually, household wiring has few series circuits so the household is not necessarily a strong pedagogical example.

 

• Useful Sites

 

• Demonstrations/experiments

A complete ‘recipe’ for setting up series/parallel circuit demonstrations for students can be found at http://www.iit.edu/~smile/ph9113.html

 

4. The amount of energy transformed in an appliance is related to the power rating of an appliance and the length of time it is used

  • describe the relationship between power dissipated, potential difference and current
  • explain the relationship Energy — VIt
  • explain why a simple scale has been used for energy rating on commercial goods and how these scales relate to potential difference and current

     

• Skills

discuss ways in which electrical consumption in households could be reduced

 

• Useful Sites

 

• Demonstrations/Experiments

First hand investigation of an electric heating coil using ‘homemade" resistance wire coil, lab thermometer. See UNSW School of Physics suppliers page at

www.phys.unsw.edu.au/hsc

 

5. Electric currents also produce magnetic fields and these fields are used in different technologies in the home

  • assess the impact of applications of magnetic field on society

 

• Skills

explain an application of magnetic fields in pest control

 

• Problems

Electromagnetic field is more relevant here. Most electronic pest control devices claim to operate via ultrasonics, those using hybrid ultrasonic/electromagnetic principle are far fewer and suspect.

 

• Useful Sites

 

• Demonstrations/Experiments

Simple, inexpensive electromagnets can be wound with insulated copper wire on an iron rod (nail). Can be used to pick up specified weight (paper clips?). Again see

 


 

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