~~NOTOC~~ {{:electricity:electricity-banner-790x50.jpg|Electricity Banner}} ====== Making Electro-magnetic Effects Visible ====== //Traditional physics texts develop ideas and concepts in a hierarchical structure. Authors assume that the proper way to understand the subject is by working your way up through a web of ideas, from simple stuff at the bottom to higher concepts at the top. A serious defect in that approach to writing school-level physics is that by keeping it simple at the basic level we can also make it wrong.// (( University of Sydney https://www.researchgate.net/publication/242589441_Understanding_Energy|Ian Sefton - Understanding Energy)) //Electromagnetism// is a branch of physics involving a type of physical interaction that occurs between electrically charged particles. **Electromagnetic fields include:** * Electric fields * Magnetic fields * Light **Electromagnetism is one of the four fundamental interactions (commonly called forces) in nature.** ((Electromagnetism - https://en.wikipedia.org/wiki/Electromagnetism)) The interaction between electricity and magnetism (electro-magnetic effects are difficult to understand, to see, touch or otherwise experience at first-hand. Contrary to our intuitive understanding about how things work in our everyday world, charged particles, such as electrons, move slowly through matter with a drift velocity of a snail (a fraction of a centimeter per second), but fields propagate at the speed of light (approximately 300 thousand kilometers in a second). **About much more than the delivery of electrical energy alone, the electromagnetic force plays a major role in determining the internal properties of most objects encountered in daily life.** Below, we present several projects using batteries, wires and magnets that demonstrate many basic concepts of magnetic machines in ways intended to make //electro-magnetic effects// more visible and better understood. This section is not about Static Electricity, so lets get that out of the way right now: === Interactive Link: To see static electricity at work, click link, rub foot on carpet and open door! === [[https://phet.colorado.edu/sims/html/john-travoltage/latest/john-travoltage_en.html|{{ :circuits:circuits-intro:john-travoltage-640x360.jpg |John Travoltage}}]] \\ === Video: Making Electromagnetic Effects Visible === {{ youtube>oU8Fe6846d4?640x360 |Making Electromagnetic Effects Visible (2min)}} * IF UNABLE TO ACCESS YOUTUBE, TRY:[[http://viewpure.com/oU8Fe6846d4|Viewpure]] * **More [[https://www.youtube.com/watch?v=ViZNgU-Yt-Y|electromagnetic effects (static)]]** //Static electricity// used to be though of as something special, or different to ordinary electricity (//current electricity//), but this is not correct and becomes immensely confusing to new learners ((Static - http://amasci.com/emotor/nostat.html)). So what to do? simply avoid using the words "static electricity". Instead, say "net charge" or "separated charge" or "the science of electrostatics". Also, never say "current electricity", instead say "charge flow" or "electric current", or "the science of electrodynamics". ((Static versus Current - http://amasci.com/miscon/curstat.html)) ---- **QUESTION: Why does a chair hold us up instead of just dropping us to the floor?** === Video: Why? - Magnetism - Richard Feynman) === {{ youtube>wMFPe-DwULM?start=236&640x360 |Making Electromagnetic Effects Visible (2min)}} * IF UNABLE TO ACCESS YOUTUBE, TRY:[[http://viewpure.com/wMFPe-DwULM|Viewpure]] \\ * A more detailed explanation of electricity **[[https://www.youtube.com/watch?v=kS25vitrZ6g|Electricity - Richard Feynman (10min)]]** \\ ====== ELECTRO-MAGNETIC MOTOR CHALLENGE ====== === Video: Simple Rotational Motors (2min) === {{ youtube>OHF-mGDrA0M?640x360 | Simple Motors (2min)}} * IF UNABLE TO ACCESS YOUTUBE, TRY:[[http://viewpure.com/OHF-mGDrA0M|Viewpure]] * **Carousel and other examples of [[https://www.youtube.com/embed/yUToL9WAK8I?start=60&end=100|homopolar motors]] and the [[https://www.kjmagnetics.com/blog.asp?p=homopolar-motors|detailed theory]]** ---- === Video: LPS Electric Motor Challenge (2min) === {{ youtube>it_Z7NdKgmY?640x360 | LPS Electric Motor Challenge (2min)}} * IF UNABLE TO ACCESS YOUTUBE, TRY:[[http://viewpure.com/it_Z7NdKgmY|Viewpure]] \\ ---- ++++ THE LPS ELECTRIC MOTOR CHALLENGE (Read more...)| **Materials** will be supplied to each group, including: MOTOR - A single length of copper wire BATTERY - A single 1.5V AA or similar battery MAGNET - A single magnet OPTIONAL - Metal bolt/screw (to use as a bearing to allow for rotation) METHOD - Each team will be allocated a length of insulated copper wire max - 300mm length. Wind a coil leaving approximately 40mm at each end. - **[[https://www.youtube.com/watch?v=it_Z7NdKgmY|Example 1 Coil and paperclips]]** - **[[https://www.youtube.com/watch?v=syKJg-vj3I8|Example 2 Coil and paperclips]]** - **[[https://www.youtube.com/watch?v=syKJg-vj3I8|Example 3 Coil and paperclips]]** **Circuit Design** can be completed using only the materials supplied in the list above: - Students build an electric motor using only one battery. one magnet and one length of wire. - The circuit must include a, student built, pressure/touch switch' to turn the motor on/off. - Students must find a way to measure the speed / efficiency of the motor. - Students will appoint two judges. - The motor that is judged to have spun the fastest OR most efficiently will win. - The final score for each group will be the best of the three tries (at discretion of judges). - The judges decision is final. * https://www.youtube.com/watch?v=y00fPzC-xiA EXAMPLES: * Other [[https://www.youtube.com/watch?time_continue=119&v=OHF-mGDrA0M|Simple homopolar motors]] * Magnet information, safety and [[http://www.coolmagnetman.com/magcare.htm|magnet care]] BATTERIES: * Common [[https://en.wikipedia.org/wiki/List_of_battery_sizes|1.5V battery sizes]] * AAA = 10.5D x 44.5L (0.41x 1.75") * AA = 14.5D x 50.5L (0.57" x 1.99") * C = 26.2D x 50.0L (1.03" x 1.97") * D = 34.2D x 61.5L (1.53" x 2.42") ++++ ---- === Simple solenoids (linear motors) === This section introduces is an example activity where students build a [[https://en.wikipedia.org/wiki/Solenoid|solenoid]]. Solenoids appear practically everywhere, from car door locks to doorbells, from diskette drive ejectors to fuel injectors. The only difference is that most solenoids limit the range of travel, and usually have a spring return. A [[https://en.wikipedia.org/wiki/Solenoid|solenoid]] is a coil wound into a tightly packed helix (spiral). In physics, a //solenoid// refers to a coil whose length is substantially greater than its diameter, often wrapped around a metallic core, which produces a uniform magnetic field when an electric current is passed through it. This type of solenoid is also an example of a simple [[https://en.wikipedia.org/wiki/Linear_motor|linear motor]]. A linear motor-style, [[https://en.wikipedia.org/wiki/Solenoid#Electromechanical_solenoid|electromechanical solenoid]] is: * Scalable to very large applications, possibly as large as a mass driver to put payloads into orbit. It's a keen space-age toy. * Has no moving parts -- there's the magic of invisible forces at work. * Requires no special construction techniques or unusual tools. * Winding coils is fun and relaxing (at least for the first few!). Even small coils are remarkably powerful. === Fig. Solenoids - Electromagnet field for a simple coil: === {{:2018:electricity:coil_basic.gif|Simple coil}} {{ :2018:electricity:wireloop_field2.gif|Simple Field}} * University of Surrey, [[http://info.ee.surrey.ac.uk/Workshop/advice/coils/air_coils.html |Air Coil Design]] \\ ====== LPS MAGNETIC ROCKET CAR CHALLENGE ====== Each group must design an electro-magnetic coil and a touch switch to activate and power a magnetic rocket car. The teacher will provide a standardised test system that includes all components EXCEPT the rocket power coil. Each group will take turns to hand their own //power coil// to the teacher, who will add the coil to the test system to power a rocket car over a set course. The coil that powers the test car for the greatest measured distance will win decide the winning group for this challenge. Each winning group member will have the opportunity to be photographed wearing //The Hat Of Power//. === Video: Magnetic Rocket Car === {{ youtube>r21ybCwXMjo?start=120&end=146&640x360 |Magnetic Rocket Car (2min)}} * IF UNABLE TO ACCESS YOUTUBE, TRY:[[http://viewpure.com/r21ybCwXMjo|Viewpure]] \\ ---- ++++ THE LPS MAGNETIC ROCKET CAR CHALLENGE (Read more...) | * https://www.youtube.com/watch?v=r21ybCwXMjo * https://www.youtube.com/watch?v=1zL8QLL6y7Y **Materials** ELECTRO-MAGNETIC POWER COIL - Each group will be given the **a three meter length of 0.63mm enameled copper wire** (the same length and type of wire for each group). * The finished coil should have a diameter of 16 to 20mm - an approximate circumference of 60mm per turn - An //AA// size battery has a diameter of 14.5mm) * A length of 50mm should be left out of the coil at each end (to allow for connection to a battery) * The end of the coil can be looped twice around itself (to stop the coil unwinding when done). METHOD - Students must design and build an electromagnetic power coil and momentary 'on' switch. * The design of the coil will affect how efficiently it may power the test car. The design of the switch will also affect the efficiency of the coil. Factors effecting efficiency of coil include; Position, Turns, Length, Iron, Voltage ((Barry's Coilguns - https://www.coilgun.info/mark2/construction.htm)) * Both ends of the coil will need to connect to an electrical test circuit. * The pressure switch will need to be activated for only a short period (1 second or less). RULES: Each group may choose to power the 'default' test car or, alternatively, any one of the other designated test cars. Each coil will be inserted into the experimental system and used to power the test car. The best of three runs will be counted. The coil that has been measured and judged as powering an approved test car the farthest distance will win. MAGNET SAFETY - Only a teacher or nominated adult may operate the test. Students must hand their power coil and switch to the teacher/ adult assistant for connection to the test rig. The rocket car is fitted with Neodymium (rare earth) magnets. **It is very important to keep all metal objects at least 1 metre away from any of the cars and the test track**. Bringing magnetic items closer than 1 meter may result in serious injury. Don't do it! Enamel Copper Wire Spool (100g): * 0.63 = 36 metres * 0.50 = 57 metres ++++ ---- ---- ++++ The LPS ADVANCED SINGLE WIRE MOTOR CHALLENGE (Read more...) | **Materials** will be supplied to each group, including: MOTOR - A single length of wire (cut into 3 pieces) BATTERY - A single 1.5V AA or similar battery METHOD = Find length of wire needed by converting //winding form// diameter to circumference [[https://www.easycalculation.com/analytical/diameter-to-circumference-calculator.php|calculator]] **Each team will be allocated a length of insulated copper wire, cut into three lengths:** THE TOTAL WIRE LENGTH FOR EACH MOTOR = **2,680mm** - **Wire length one 1850mm - 1 x base coil** = 15 turns x 110mm circ. (D cell batt. 35dia = 1650mm) + 200mm spare = Sub-total - **Wire length two 150mm - 1 x support wire** = Sub-total - **Wire length three 875mm - 1 x spinning coil** = 15 turns x 45mm circ. (AA cell batt. 14.5mm = ) + 200mm spare = Sub-total Common [[https://en.wikipedia.org/wiki/List_of_battery_sizes|1.5V battery sizes]] * AAA = 10.5D x 44.5L (0.41x 1.75") * AA = 14.5D x 50.5L (0.57" x 1.99") * C = 26.2D x 50.0L (1.03" x 1.97") * D = 34.2D x 61.5L (1.53" x 2.42") **Circuit Design** can be completed using only the materials supplied in the list above: - The circuit must include a, student built, pressure/touch switch.' - A motor built from only one battery and one length of wire (cut into three pieces) - Each group will be allowed up to three attempts - Students must find a way to measure the speed / efficiency of the motor. - The motor that is judged to have spinned the fastest or most efficiently will win. - The final score for each group will be the best of the three tries. EXAMPLES: * Ultimate [[https://www.youtube.com/watch?v=y00fPzC-xiA|DIY single wire motor]] * Other [[http://www.arvindguptatoys.com/motor-and-generator.php|simple motors]] ++++ ---- ---- ++++ INVESTIGATE MAGNETIC FIELD IN A SLINKY (Read more...) | Purpose - To investigate the relationship between magnetic field inside a solenoid and the number of turns per metre of the solenoidÍž To determine the value of the permeability of free space constant. Introduction and Theory A solenoid is made by taking a tube and wrapping it tightly with many turns of wire. When a current passes through the wire, a magnetic field is present inside the solenoid. Solenoids are used to produce magnetic fields. They are seen in many electronic circuits, in magnetic resonance imaging machines in hospitals, etc. In this activity, we will explore how the number of turns per metre affects the magnetic field inside the solenoid. A metal Slinky will serve as our solenoid. The Slinky represents a solenoid very well and is readily available. More importantantly, it is flexible so we can easily change the number of turns per metre. We measure the magnetic field inside the Slinky by inserting a magnetic field sensor between the coils of the Slinky. The same measurements also allow us to calculate the permeability constant * http://langaraphysics.com/1225slinky.pdf ++++ ---- === Ideas For Developing Deeper Understanding === Questions asked in class. Some more information about electro-magnetism, including heat, temperature, fire and photosynthesis: * NESA K-10 -Physical World ((NESA K-10 Physical World -http://syllabus.nesa.nsw.edu.au/science/science-k10/content/974/)) * [[https://www.exploratorium.edu/snacks/electric-current-model|Use magnets to model the motion of electrons + model electric current]] * [[https://www.exploratorium.edu/snacks/stripped-down-motor|Build a simple electric motor]] * [[https://www.exploratorium.edu/snacks/charge-carry|Reliably generate static electricity]] * [[https://www.youtube.com/watch?v=yE8rkG9Dw4s|Why you can't touch anything]] * [[https://www.youtube.com/watch?v=N1pIYI5JQLE|Richard Feynman on fire!]] * [[https://www.youtube.com/watch?v=1pfqIcSydgE|What is fire (Minute Physics]] * [[https://www.youtube.com/watch?v=yxBTEMnrZZk|Temperature versus Heat (Eureka)]] * [[https://www.youtube.com/watch?v=QwUq8xM_8bY|DONG / VSauce - Lenz's Law (mostly (electro)magnetism)]] * NESA K-10: Living world ((NESA K-10: Living world - http://syllabus.nesa.nsw.edu.au/science/science-k10/content/984/ )) * [[https://www.youtube.com/watch?v=NJwXYZ4GryA|Photosynthesis]] * [[https://www.youtube.com/watch?v=_RSKI5A_lsg|The Magical Leaf: The Quantum Mechanics of Photosynthesis]] ---- === References: ===