1. Electricity
Introductory Physics
Canadian Academy
Image from: http://www.penguintutor.com/electronics/electrical-safety

2. Electricity
Unit Questions: “How can we power a community?”
Enduring Understandings:
• Electricity can be harnessed for the benefit of humans
Areas of interaction:
Human Ingenuity
The development of electrical technologies revolutionised culture
Environments
Can we maximise efficiency in order to maximise sustainability?
Criterion Assessment Tasks
B: Knowledge & Formaive: Current Elecricity Flipbook
Understanding

3. Electrostatics – Whaddya Know?
Think, share, scribble it on a whiteboard.

4. Draw an Atom!
What are the names, sizes, charges and positions of the components?
What is the relevance of this to electricity?

5. Discover electrostatics demonstrations
Try these demonstrations with your group and keep notes on the sheets provided.
Can you explain your observations? Use the resources on the GoogleSite if you need to.
• Electrification • Charged tapes
• Balloon tricks
• Opposite sides of an acrylic sheet
• Triboelectric series
• Electroscopes
Image: balloon static from http://www.education.com/science-fair/article/physics_pickup/
Image: simple electroscope from http://www.school-for-champions.com/science/static_detection.htm
Image: balloon & water from http://www.thenakedscientists.com/HTML/content/kitchenscience/exp/bending-water-static-attraction/

6. Can you explain what’s happening?
Try this visualisation from PhET Labs.
http://phet.colorado.edu/en/simulation/balloons
Find out more about the triboelectric series.
Do electrons move from the balloon to the
jumper or the other way round – why?
What is happening in the electroscope?
What happens when the leaves get ‘stuck’ apart?
How could you get them to go back to their original
positions? Why does this work?
Image: simple electroscope from http://www.school-for-champions.com/science/static_detection.htm

7. Properties of Charge Add electrons to each of
these systems:
Charge is conserved: + + + +
Charge cannot be created or destroyed. + + +
It can only be transferred (by charge carriers*). + + +
neutral
Charge is quantized: + + + +
Charge is found in a smallest “package size” + + +
called the elementary charge, e (charge on one + + +
proton or electron) measured in Coulombs (C). strong negative charge
*electrons + + + +
+ + +
+ + +
weak positive charge

8. Properties of Charge Add electrons to each of
these systems:
Charge is conserved: + -+ - +- +
Charge cannot be created or destroyed. - + - + - +-
It can only be transferred (by charge carriers*). + - + - -+
neutral
Charge is quantized: - + - + -+ -+
-
Charge is found in a smallest “package size” - - - - +- - +
+ -
called the elementary charge, e (charge on one + - -- -- - +
+ -
proton or electron) measured in Coulombs (C). strong negative charge
*electrons + - + +- +
Remember: electrons can be
added or removed, but -+- + +
-
protons stay where they are. + +- - +
weak positive charge

9. Methods of generating a static charge
Only electrons move!
Friction
Transfer of electrons from one material to a
different one through friction. Electrons
are ‘peeled’ off one by the other.
The triboelectric (or electrostatic) series tells us
which materials have a greater tendency to
hold on to their electrons and which have a
greater tendency to lose their electrons. http://phet.colorado.edu/en/simulation/balloons
electron losers electron holders
+ -

10. Triboelectric series
electron losers electron holders
+ -
What happens when…?
1. Aluminium is rubbed against human hair?
2. Fur is rubbed against styrofoam?
3. Teflon is rubbed against styrofoam?
4. Dry hands are rubbed against polyethylene?
Where do leather, nylon, polyester and hard rubber fit on the series?
Find out more http://regentsprep.org/Regents/physics/phys03/atribo/default.htm

11. Triboelectric series
electron losers electron holders
+ -
What happens when…?
1. Aluminium is rubbed against human hair?
2. Fur is rubbed against styrofoam?
3. Teflon is rubbed against styrofoam?
4. Dry hands are rubbed against polyethylene?
Where do leather, nylon, polyester and hard rubber fit on the series?
Find out more http://regentsprep.org/Regents/physics/phys03/atribo/default.htm

12. Methods of generating a static charge
Only electrons move!
+- - - - - - - -+ +- - +
strong negative charge neutral
Conductiona charged material
Transfer of electrons from
to another material through contact.

13. Methods of generating a static charge
Only electrons move!
+- - - - - - - -+ +- - +
electrons move until they are
balanced in both objects
Conduction
Transfer of electrons from a charged material
to another material through contact.
Conductors are materials which allow Insulators are materials which do not
electrons to flow freely through them. allow electrons to flow freely.
examples: examples:

14. Methods of generating a static charge
Only electrons move!
+- - - - - + +--- -- +
negative charge negative charge
Conduction
Transfer of electrons from a charged material
to another material through contact.
What would happen if a strong positive charge
made contact with a neutral object?

15. Methods of generating a static charge
neutral
- + -+
+- - - - - - - -+
strong negative charge
+- +-
insulator
Inductionbetween two materials
Does not use contact
but does require one to be grounded.

16. Methods of generating a static charge
+ + -- separation of
+- - - - - - - -+ charge: electrons
strong negative charge
+ + -- are repelled
insulator
Induction
Does not use contact between two materials
but does require one to be grounded.

17. Methods of generating a static charge
+ + electrons are
+- - - - - - - -+ conducted into the
strong negative charge
+ + ground
insulator
The ground is then
disconnected
Induction
Does not use contact between two materials
but does require one to be grounded. The Earth is so big it is
always considered neutral

18. Methods of generating a static charge
+ + object is left
+- - - - - - - -+ positively charged
strong negative charge
+ +
insulator
Induction
Does not use contact between two materials
but does require one to be grounded.

19. Methods of generating a static charge
Only electrons move! Charge is conserved!
Friction
Transfer of electrons from one material to a The triboelectric (or electrostatic) series tells us
different one through friction. Electrons which materials have a greater tendency to hold
are ‘peeled’ off one by the other. on to their electrons and which have a greater
tendency to lose their electrons.
Conductiona charged material
Transfer of electrons from
Contact is needed. Electrons flow more freely
through good conductors. There is net flow
until there is balance of charge between the
to another material through contact.
two objects.
Inductionbetween two materials
Does not use contact
Separation of charge occurs as elecrons can
move but protons cannot. By cutting the
but does require one to be grounded. ground, the induced object remains charged.

20. Properties of electrostatic charge
‘Like’ charges repel. ‘Opposite’ charges attract.
Only electrons have the freedom to move through a material.
Observe and explain:
Wool is used to charge an acrylic rod. It is brought
near the neutral pithball, attracting it.
It touches the pithball, after which it is repelled.
Why does this happen?
Which force is stronger – the electromagnetic force
or gravity? Explain your reasoning.
Image: pithball electroscope from http://en.wikipedia.org/wiki/Electroscope

21. Build your own simple electroscope
What materials do you need?
Test it and get some photos
- in the resting state
- when approached by a negatively
charged object
- when approached by a positively
charged object
Image: simple electroscope from http://en.wikipedia.org/wiki/Electrometer

22. How does the electroscope work?
Negatively charged rod
+
Induced charge separation
+ - electrons in the rod repel electrons
+ -
in the electroscope
electrons are forced into the leaves
- - negatively charged leaves repel
- -
- Negatively charged leaves
Image: simple electroscope from http://en.wikipedia.org/wiki/Electrometer

23. How does the electroscope work?
Positively charged rod
- --
Induced charge separation
-
- protons in the rod attract electrons in
the electroscope
- electrons move away from the leaves
- positively charged leaves repel
+
Positively charged leaves + +
Image: simple electroscope from http://en.wikipedia.org/wiki/Electrometer

24. Can we measure charge?
How could we use an electroscope to
measure the charge of an object?
Image: needle electroscope from http://www.farraguttn.com/science/milligan/APPhys/AElctLab.htm

25. Properties of Charge
Charge is conserved:
Charge cannot be created or destroyed.
It can only be transferred (by charge carriers*).
Charge is quantized:
Charge is found in a smallest “package size”
called the elementary charge, e (charge on one
proton or electron) measured in Coulombs (C).
*electrons
Image: needle electroscope from http://www.farraguttn.com/science/milligan/APPhys/AElctLab.htm

26. Electrostatic discharges
Explain what is happening in these animations.
They are different!
http://phet.colorado.edu/en/simulation/travoltage http://regentsprep.org/Regents/physics/phys03/atribo/
What environmental conditions favour static shocks?
What can you do to reduce the chance of getting a static shock?
Image: needle electroscope from http://www.farraguttn.com/science/milligan/APPhys/AElctLab.htm

27. What causes lightning?
http://www.youtube.com/watch?v=H_MG__53wsM
Image: '¡Rayos!' 27
http://www.flickr.com/photos/11039104@N08/2926143475

28. Make some lightning!
Try this in a darker part of the class. Be careful.
Use the styrofoam and rabbit fur to generate a static charge.
Touch the aluminium disc against the styrofoam.
Touch your finger against the disc.
What happens when the disc approaches
the electroscope? Why?

29. Little house on the prairie
This little house is exposed and prone to being struck by lightning.
Explain why – and then explain why the owners should install a lightning rod.
Image: little house from http://www.supercoloring.com/pages/little-house-in-ukraine/

30. Be safe at the petrol pump!
Watch this video and suggest what could have happened.
What types of electrostatic transfers took place?
http://www.youtube.com/watch?v=tuZxFL9cGkI

31. What do the Mythbusters say about it?
http://www.youtube.com/watch?v=uw6-PhvcS3M

32. Be safe at the petrol pump!
This guy is trying to bring leather pants back into fashion.
He also loves hairspray and his boots with thick rubber soles.
What advice would you give him when he goes to the gas
station in his super-cool Lada Samara with polyester seating?

33. Are cell phones dangerous at petrol pumps?
http://www.youtube.com/watch?v=QkJdaU92Ln8

34. Are cell phones dangerous at petrol pumps?
Don’t risk it – follow the rules!
http://www.youtube.com/watch?v=QkJdaU92Ln8

35. Is this plausible? Could you really cook an egg with one finger?
http://www.youtube.com/watch?v=QT789U0Ld60

36. Is this plausible? Could you really power a house with static electricity?
http://www.youtube.com/watch?v=scUosAkxlvo

37. Current Electricity Construct and explain.
http://phet.colorado.edu/en/simulation/circuit- http://www.slideshare.net/gurustip/current-
construction-kit-ac-virtual-lab electricity-11092690
Build circuits using this simulation and try to replicate them with the materials in
the lab. Use the battery (DC) only.
Download and edit the Current Electricity presentation above.
Complete the questions in the presentation and submit.

38. Why does the bulb glow?
This cross-section models the flow of electrons through a
lamp. The large dots represent atoms in the filament.
Open the animation and find out:
1. What do the red dots and the small yellow dots represent?
1. As the current increases, what happens to:
a. The flow of electrons?
b. The rate of collisions with the filament atoms?
c. The energy carried by the flowing electrons?
The resistance of the filament remains constant.
If it were replaced with a bulb of greater resistance, would the
bulb glow brighter, dimmer or stay the same? Explain why.
Resistance at the Molecular Level:
http://micro.magnet.fsu.edu/electromag
/java/filamentresistance/

39. Note in this example that the large yellow dots remain constant.
Resistance These are atoms in the filament which impede the flow of the
electrons – they cause resistance to the current.
Some materials have greater electrical resistance than others.
Wires have resistance, though this is not apparent in the
simulations we have used.
Resistance can be increased by:
• Heating the wire or resistor
(atoms vibrate more and so are more likely to impede
the flow of electrons)
• Making the wire thinner
• Making the wire longer
Increasing the resistance of a bulb does not make it brighter.
Resistance at the Molecular Level:
http://micro.magnet.fsu.edu/electromag
Remember that electrons are flowing round the whole
/java/filamentresistance/ circuit. An increase in resistance slows the flow of electrons
and the bulb is dimmer.
Energy-efficient bulbs have lower resistance than other
bulbs due to the materials they are made from.

40. Arrange this equation based on your own observations.
A
= Ω
V
RIV
potential difference
resistance
current
40

41. Arrange this equation based on your own observations.
V
potential difference
I= RA
current
V
Ω
resistance
41

42. Electrical Misconceptions
A used battery weighs less than
a new battery because it has
used up all its charge. .
A used battery weighs
less than a new battery
because it has lost its
electrons. .
A used battery does not
weigh less than a ‘full’
battery.
Image from http://www.edupics.com/image-battery-i10096.html

43. Electrical Misconceptions
The electrons move quickly, but bulb A is
closer to the battery, so will light up first..
A B C
Clipart people from: http://www.clker.com/search/krug/1

44. Electrical Misconceptions
Bulb C is closer to the negative terminal of
the battery, so it will get the electrons first
and will glow more brightly. Bulb B will be
dimmer and A will be dimmest.
A B C
Clipart people from: http://www.clker.com/search/krug/1

45. Electrical Misconceptions
The current that returns to the battery is
almost zero because most of the current
has been used by the bulbs.
Clipart people from: http://www.clker.com/search/krug/1

46. Electrical Misconceptions
The bulb has burned out.
If I replace it with a bulb of different
resistance it will be the same brightness.
This is because the battery is the same.
Clipart people from: http://www.clker.com/search/krug/1

47. Electrical Misconceptions
If I add bulb X to my circuit, it will only affect
the brightness of bulb B.
A B C
X
Clipart people from: http://www.clker.com/search/krug/1

48. Electricity & Magnetism – what’s the link?
When I bring a disconnected wire close to the compass…
When I bring a connected wire close to the compass…
Clipart people from: http://www.clker.com/search/krug/1

49. Electricity & Magnetism – what’s the link?
If the current affects the compass, do
magnets affect current?
Have a go at this PhET Lab to explain the
relationship between magnetism and current.
How do we generate the electricity we use?
PhET Lab: Faraday’s Electromagnetic Experiment
http://phet.colorado.edu/en/simulation/faraday
Clipart people from: http://www.clker.com/search/krug/1

50. How is electrical current generated?
What happens when you rotate the handle with
constant motion and speed up or slow down? Why?
What happens when you move the handle back and
forth? Why?
What feels different when you connect and disconnect
the bulb? Why?
Connect up some series circuits like you have created
What’s happening in here?
in the ‘Current Electricity’ tasks. Do the same rules
appear to be true?
What happens if you connect a second hand-generator
to the circuit and let it go? (Don’t grab the handles of
both at the same time).
Hand generator from http://www.usi.edu/stem/Equipment_page.asp

51. 51

52. Renewable vs Non-renewable energy
Explain the problems we face in the world regarding energy use.
With a partner and a GoogleDoc or whiteboard find out about two forms of generating
electricity: one based on combustion of fossil fuels and one renewable.
Thinking from a One World perspective, compare the two methods.
• What are the pros and cons of each?
• How do they work?
• To what extent is the renewable source a viable alternative to the fossil-
fuel based source?
What directions could Japan take to ensure a sustainable source of electricity?
52

53. What do you think?
Ideas based on
Concept Cartoons:
http://www.conceptcartoons.com
Clipart people from: http://www.clker.com/search/krug/1

54. Some basic circuit symbols
You can use these to build the circuits on the next slides.
wire cell battery
junction
+ - + -
cathode anode
electron flow
bulb/ lamp resistor
conventional current
What do these two components measure?
switch
V A
voltmeter ammeter

55. For more resources.
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