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====== ELECTRICITY EXPERIMENT #1 ======
Start and end each session with a [[http://pz.harvard.edu/projects/visible-thinking|visible thinking]] learning task - [[https://www.youtube.com/watch?v=IJSVZBr6Mr0|what I used to think and what I think now]] - to help implement {{https://www.nwea.org/blog/2012/dylan-wiliam-the-5-formative-assessment-strategies-to-improve-student-learning/|the Five Formative Assessment Strategies}} to improve student learning.
**Learning Tasks That Elicit Evidence of Learning** ((Dylan William - Formative assessment https://www.nwea.org/blog/2012/dylan-wiliam-the-5-formative-assessment-strategies-to-improve-student-learning/ ))
Open your Science book/Journal/sheet and briefly write down your name, the experiment title and date:
* Your Name(s): -----------------, ----------------
* The Title: Electricity #1
* Short Date: dd/mm/yyyy
Please spend five to ten minutes to write down what you think about each of the statements below (you may use drawings/images or refer to other sources of information)
- Are 'electricity' and 'electrical energy' just different ways of saying the same thing?
- Does an electrical generator make electricity?
- Does a battery store electricity?
- Does a circuit have to be closed (unbroken) for electricity to flow?
* At the end of this session, write down new answers to the same questions.
* Have you changed your mind about any of the answers you gave at the beginning of the session?
=== Why we focus on 'understanding the principles' rather than on 'learning the facts' ===
{{ :2018:heat:experiment-4:einstein.jpg?117|}}
* **//“Never memorize something that you can look up.”// Albert Einstein - ((https://www.goodreads.com/quotes/24194-never-memorize-something-that-you-can-look-up))**
* If your teaching/learning focuses on an understanding of the principles, you don't need to remember the facts - just look them up. No matter how many facts you remember, there is no guarantee that you will ever understand the principles that underlie them.
* All that you need to understand about the current scientific view about [[http://www.vicphysics.org/documents/teachers/2002Sefton.pdf|electricity]] is ...
=== Everything in the universe is made up of matter and energy. ===
* **//“The beauty of a living thing is not the atoms that go into it, but the way those atoms are put together”//** ((Carl Sagan - https://www.youtube.com/watch?v=XGK84Poeynk))
* **Matter** is made up of atoms and molecules (groupings of atoms).
* **Energy** causes atoms and molecules to always be in motion - either bumping into each other or vibrating back and forth (This is a handy starting point, but the concept of energy is a work in progress and has no simple definition). ((University of Sydney [[https://www.researchgate.net/publication/242589441_Understanding_Energy|Undesranding Energy - Ian Sefton]] ))
* The motion of electrons creates a form of energy called //electrical energy// ((University of Sydney [[http://www.vicphysics.org/documents/teachers/2002Sefton.pdf|What The Textbooks Don't Tell You - Ian Sefton]] )).
* Energy can take on many forms and can change from one form to another.
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INTRODUCTORY QUESTION(S):
- When you build a house, is all of the electricity already in the wire?
- Does the electricity company does not make, supply or sell any electricity.
- When you buy a battery, is all of the electricity already in the battery and never gets used up.
- Do batteries store or create electricity?
- What is a switch?
- Can electricity travel through a switch that is turned 'off' (travel through an //open circuit//)?
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====== The six most important concepts about electricity ======
**1. There are only two ways of creating an electric field.**
* One way is to have a changing magnetic field, as in the phenomenon of electromagnetic induction. That is what generators do.
* The other way involves separation of positive and negative charge. That is what batteries do.
**2. Electrons travel slowly and do not carry electrical energy.**
* In //Direct Current// (DC) circuits, [[http://www.vicphysics.org/documents/teachers/2002Sefton.pdf|Electrons]] travel slowly.
* In Alternating Current (AC) circuits, electrons don’t go anywhere much; they just jiggle back and forth. So they can’t carry energy from one place to another.
**3. Electrical circuits do not require a closed loop:**
* Electrical circuits do not require a complete conducting loop before a current can exist (except, a continuous conducting loop is required to maintain a steady current in a circuit)
**4. Current is not a flow of charge:**
* Current is usually defined as flow of charge. However, since charge is not something that exists on its own but is a property of objects, current is more properly defined as a flow of charged particles.
**5. Batteries do not create or store electricity:**
* In circuits driven by batteries the push on the conduction electrons comes ultimately from a **//separation of charge//** produced and maintained by the battery,
**6. Electrical Energy Travels Outside The Wire:**
* The idea that the electromagnetic field both stores and transmits energy is the key to the explanation of how energy gets from the battery to the light globe. The four conceptual characters: charge, current, electric field and magnetic field whose complex relationships are governed by four equations (known as Maxwell’s equations).
* Current is just charge in motion while electric field and magnetic field are but two aspects of a fundamental entity which can be called electromagnetic field.
**SUMMARY:**
* Electrons travel very slowly in both directions between battery and globe, and in a circuit they generally don’t go anywhere much but energy is transferred very rapidly and it can get across gaps in the conducting path. The same goes for forms of current other than electron drift.
* Electrons don’t have Potential Energy (PE) of their own (the PE is the property of the whole system).
* Electrical energy does NOT flow inside metal wires.'As a consequence of having a current in the wires, there is a magnetic field in the space around the wires. It is this combination of electric field and magnetic field in the space outside the wires that carries the energy from battery to globe.((Sefton - Sydney University Physics 2002))
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++++ Q2.3 CLICK HERE FOR A SCIENTIFIC EXPLANATION:|
* Generators don't produce 'electricity', they are pumps.They move electrons backwards and forwards. This movement results in an electromagnetic field which provides 'electrical energy'.
* Electrical energy consists of invisible fields resembling radio waves that whiz along OUTSIDE the wires.
Generators are 'charge pumps'. They force the 'charges' found INSIDE the wires to flow along.
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====== EXAMPLE VIDEO INTERVIEW QUESTIONS ======
- Tell us a little bit about your project.
- How does your project work?
- Does your project use electricity?
- Does your project use circuits?
- Does your project use switches?
=== Video: YCC 2017 - Example Interview ===
{{ youtube>VllqyNXhsr4?start=148&640x360 |Making Electromagnetic Effects Visible (2min)}}
* IF UNABLE TO ACCESS YOUTUBE, TRY:[[http://viewpure.com/VllqyNXhsr4|Viewpure]]
++++ Q2.3 CLICK HERE TO CLARIFY MISCONCEPTION... |
MISCONCEPTION: Electricity that is generated at the power station flows inside metal wires to power outlets in homes and businesses, where it is used up by lamps and other electrical appliances.
CORRECT UNDERSTANDING: In DC circuits and in 50Hz AC circuits (including 240V and higher domestic & commercial power in Australia), the 'current' exists all through the entire wire.
Electronics students commonly assume that this means electrical energy flows INSIDE the metal wires, but this is not right.
***Physics students have a different understanding.*** The scientific explanation is that electrical energy normally doesn't flow inside of metals. In fact, the 'joules' being sent out by batteries and generators are located in empty space: they take the form of electromagnetic fields surrounding the wires.
Similarly, batteries don't supply 'electricity' - the wires themselves supply that from their own substance.
A battery is a chemically-fuelled 'charge pump'. Like any other kind of pump, a battery takes charges in through one connection and spits them out through the other.
A battery or a generator is NOT the source of the substance or 'stuff' being pumped.
As per {{:learn:electricity:quiz:sefton.pdf|this reference:}} A. Sommerfeld (1952) has pointed out, metals are good conductors of CURRENT but non-conductors of ENERGY.
Metals conduct CURRENT but space conducts ENERGY and the best conductor of electromagnetic (EM) ENERGY is the vacuum!
When we turn on a lamp or other electrical device from a remote switch, we don't have to wait for electrons to complete a journey because the electrons are not given the ENERGY in the first place.
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++++ Q2.3 CLICK HERE FOR MORE DETAILED ACADEMIC REFERENCES... |
There are two valid schools of thought about how one should conceptualise energy and energy
transfer, that I will call:
* the 'accountant’s model'
* and the 'field model'.
The accountants view energy solely as a mathematical attribute of physical systems, and it does not need any kind of conceptual model beyond that.
The story of energy transfer from the battery to the globe goes like this. When the battery is first connected to complete the circuit it pushes electrons (charge) around so that they pile up on the surfaces of some parts of the circuit, leaving a deficit of electrons, and hence a positive charge on other parts of the conductors’ surfaces. This pushing around of electrons is mediated by the electric field. The charge separation in turn produces electric field inside the connecting wires as well as in the wire filament of the light globe.
The internal electric field is directed along the axis of the wires and is responsible for producing a drift of mobile charge carriers, current, in the wires.
To explain energy transfer we need to look at what is happening outside the wires.
As a consequence of the surface charges on the wires, there is an electric field in the space outside the wires (as well as inside).
Also, as a consequence of having a current in the wires, there is a magnetic field in the space around the wires. It is this combination of electric field and magnetic field in the space outside the wires that carries the energy from battery to globe.
Once the fields are set up, the energy travels through space, perpendicular to both the electric field and the magnetic field, at the speed of light.
Energy leaves through the sides of the battery and enters the wire of the globe through the sides of the wire.
As Arnold Sommerfeld (1952) has pointed out, metals are good conductors of current but non-conductors of energy. Metals conduct current but space conducts energy and the best conductor of electromagnetic energy is the vacuum!
Reference: Science Teachers’ Workshop 2002 Understanding Circuits What the Text Books Don’t Tell You - Ian M. Sefton School of Physics, The University of Sydney
Reference: [[http://sites.huji.ac.il/science/stc/staff_h/Igal/Research%20Articles/Pointing-AJP.pdf|Energy transfer in electrical circuits: A qualitative account - 2005]]
The application of the surface charge model to a simple circuit shows that electromagnetic energy flows from both terminals of the battery, mainly in the vicinity of the wires ~and not inside them! to the load where it enters and is converted into heat at a rate obtained from Ohm’s law. © 2005 American Association of Physics Teachers.
http://sites.huji.ac.il/science/stc/staff_h/Igal/Research%20Articles/Pointing-AJP.pdf
Also see: [[http://amasci.com/elect/poynt/poynt.html|IN A SIMPLE CIRCUIT, WHERE DOES THE ENERGY FLOW?]]
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++++
====== Helicopter Pre-Takeoff Check Controller - A Project Design Challenge ======
=== Video: LPS Helicopter, pre-take-off checks ===
{{ youtube>aFDR_7Ulqbw?640x360 |Helicopter pre-take-off checks (2min)}}
* IF UNABLE TO ACCESS YOUTUBE VIDEO, TRY:[[http://viewpure.com/aFDR_7Ulqbw|Viewpure]] - ((Pre-take-off checks - https://www.helicopterground.com/blog/hover-pre-take-off-check))
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++++ THE AIRFORCE 'HELICOPTER IGNITION SWITCH' CHALLENGE (Read More...) |
Each student group will design and build a 'helicopter ignition switch' (see 'circuit design' below), and awards will be issued for achievement of various design features (see below).
A single, 'helicopter' device will be used for each group to ensure a 'fair test'.
The helicopter system will be supplied by the teacher and the sequentially connected to each of the switch systems.
The teacher and students will agree on the best way to measure and assess the ignition switch/helicopter performances.
**Awards** will be issued to:
- The group who are able to launch the helicopter and achieve the highest measured height.
- Each group who are able to design a switch circuit that will launch the helicopter.
- Each group who are able to design a switch circuit that will start the helicopter.
**Materials** will be supplied to each group, including:
* A single 1.5V AA battery.
* A single 1.5V light globe.
* Five hook-up wires with alligator clips attached to each end.
* A ball (or similar rolling 'switch activator)'
* A piece of aluminium foil
* Masking tape, scissors, paper, card and similar trash supplied on the day.
**Circuit Design** can be completed using only the materials supplied in the list above:
- The circuit must include four, student built, pressure/touch switches.'
- The switches are activated manually or by one or more rolling balls (supplied by teacher)
- Each group will be allowed up to three attempts to launch, with up to one minute to allow for modifications between launches
- The final score for each group will be the best of the three tries.
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=== NOW LET"S INTERVIEW SOME OF OUR PROJECT TEAMS ===
- Tell us a little bit about your project.
- How does your project work?
- Does your project use electricity?
- Does your project use circuits?
- Does your project use switches?
- Does your project use batteries?
=== BEFORE END OF SESSION (allow 10 minutes) ===
**Learning Tasks That Elicit Evidence of Learning** ((Dylan William - Formative assessment https://www.nwea.org/blog/2012/dylan-wiliam-the-5-formative-assessment-strategies-to-improve-student-learning/ ))
At the end of this session, write down new answers to the same three questions you answered earlier:
- Are 'electricity' and 'electrical energy' just different ways of saying the same thing?
- Does an electrical generator make electricity?
- Does a battery store electricity?
- Does a circuit have to be closed (unbroken) for electricity to flow?
* Have you changed your mind about any of the answers you gave at the beginning of the session?
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=== References ===