The Big Switch - The Role of Magnetic Fields in Motors and Generators > Essential Understandings > Essential Tasks - Do Part 1 & 2 as teacher demos. - Do Part 3 as hands-on activity for better classes. Demo equipment set-up & use: show motor/generator connected to amp meter; free-falling 100-g mass generates >500 milliamps (500 milliamperes = 0.5 amperes) [according to Ohm's law: 1.5 V / 3 ohms = 0.5 A] Students connect motor/generator to light bulb. [Turn off ceiling lights. Students must demo for teacher successful operation of system. When light bulb lights, say, "I have made fire!" Tom Hanks in "Castaway."] Refer to the following: http://www.wsanford.com/~wsanford/gr8ps/02_purple/03_the_big_switch/ extras/moving_on/electric_motor-generator.txt Test procedure for generating electric current by manually spinning propeller -- I'm guessing one cannot generate sufficient power to run a light bulb.***You can't. That said, you CAN spin propeller fast enough (one finger-flick) to drive an analog ammeter (reads ~200- to 300 milliamps).*** Pre-Lab: Show segment from video, "Einstein's Big Idea" E is for Energy ~6:30 - 21:24 London, England 1812 Michael Faraday Part 1: magnetic fields; electromagnetism - use one magnet to make another "spin" devise a way to mount a "fixed" magnet on a rotating shaft; hold two magnets near fixed magnet in order to make it spin magnetic forces of attraction/repulsion cause motion (mechanical energy) attract(ed)/repel(led) attraction/repulsion attractive/repulsive P.O.D.: Q. Which of the following orientations of magnets would result in the greatest attraction between the two magnets? Fixed Set Number 5: 3* (polarity vs. magnets) [A] 1317-1320 http://www.wsanford.com/~wsanford/gr8ps/02_purple/assessment/ VA-SOL_Graphics/1317.gif Vernier magnetic field sensor: A magnetic compass and the Vernier magnetic field sensor are both devices that detect magnetic fields. Set the selector switch to "Low" sensitivity; keep white dot toward the magnet, move the probe from one end of the magnet to the other. The magnetic field sensor reading is much higher at the ends of the magnet. At one end of the magnet, there is a positive magnetic field reading; negative at the other. ***S pole is positive; N pole negative*** units: mT (millitesla) http://en.wikipedia.org/wiki/Millitesla Magnets have north & south poles that produce magnetic field (force) lines. [Vernier: The maximum output occurs when the white dot on the sensor points toward a magnetic south pole.] P.O.D.: Where is magnetic field strongest? Weakest? Absolutely strongest = S. Pole. http://www.wsanford.com/~wsanford/gr8ps/02_purple/assessment/ VA-SOL_Graphics/2341.gif - Show VA SOL graphic: - use a magnet & iron filings to visualize magnetic field ("Mr. Woolly" or "Woolly Willie") See also: - http://en.wikipedia.org/wiki/Magnetic_field - http://en.wikipedia.org/wiki/Image:Magnet0873.png http://ph99.bc.edu/educational_resources/demos/home.html B-S1 : 2D Magnetic Field Lines B-S2 : 3D Magnetic Field Lines <-- cool! - Use an iron nail, coil of wire, and a battery to create an electromagnet. Wrap the wire around the nail 30-40x(***). http://www.wsanford.com/~wsanford/gr8ps/02_purple/assessment/ VA-SOL_Graphics/0449.gif ***Demo of electromagnet - add a knife switch to complete circuit*** ***Wrap wire less & more times; explore relationship between number of coils and field strength.*** <-- test results inconclusive; re-do P.O.D.: Fixed Set No. 3, Ques. No. 6 (0449) re: how to increase strength of magnetic field. Vernier magnetic field sensor: Set the selector switch to "High"; move probe along length of nail [and coil of wire?] BEFORE and AFTER demo. Remove its iron core; detect the presence of its magnetic field using Vernier magnetic field sensor. Note: Once an iron nail has been made into an electromagnet, it will remain slightly magnetized. == Part 2 & 3: simple motor/generator As it turns out, "motor-generator" [motor/generator] is an actual term in common use: http://en.wikipedia.org/wiki/Motor-generator See also: http://en.wikipedia.org/wiki/Electromagnetic_induction Note: It might be better to use the following phrase: "electric motor/generator" [since one device is the inverse of the other] Use overhead transparency of electric fan/wind turbine graphic in TRG; Intro this part of lesson w. related P.O.D.: Q. Make an energy "chain" that shows the energy transformations that occur for each of the devices shown (on the overhead). A. motor: produces mechanical energy (motion) energy "chain": electrical energy --> mechanical energy (kinetic) generator: produces (generates) electrical energy energy "chain": mechanical energy (kinetic) --> electrical energy -- demo essential parts of motor ("guts"): both a motor and a generator contain permanent magnets (or electromagnets) and coils of wire (electromagnet) wrapped around an armature, mounted on the rotor (motor shaft). Also commutator & brushes. Parts of a motor: rotor (rotating part); stator (stationary part); armature; commutator & brushes Note: Reversing polarity of battery connections (connecting leads to +/- and -/+) to motor/propeller makes motor spin either clockwise or counterclockwise ***determine which connections cause cw & ccw rotation*** magnet passing thru a coil of wire http://www.wsanford.com/~wsanford/gr8ps/02_purple/assessment/ VA-SOL_Graphics/0258.gif [similar to "Faraday Flashlight"] -- Unsorted Lab Observations: > magnetic field sensor readings: = bar magnet -5.1 mT (N) ----- (S) +5.9 mT = iron nail -8.0 mT (head) ----- (point) 6.3 mT <-- did not note +/- battery connections ***FEB '07 - I *think* the negative battery terminal produces the negative electromagnet pole; positive battery terminal produces the positive electromagnet pole.*** > battery + motor propeller counterclockwise: red(-)/black(+) conventional orientation of jumper leads --> clockwise: black(-)/red(+) > motor/generator: depending upon direction motor shaft is turned (either cw or ccw), amp meter will read either negative or positive == DuraPro MegaBRITE crank light ("Cranky the Flashlight") http://www.flashlightreviews.com/reviews/durapro_crank.htm "...there is a battery in there. It's a Lithium Ion 2032 3.6V coin cell which is charged by the crank." http://www.durapro.com/product.asp?catalog_name=durapro&category_name= more&product_id=10-131 <-- essentially a useless hyperlink See also "Faraday Flashlight" Google Search: "faraday flashlight" "faraday flashlight" how does it work? original source: http://www.faradayflashlight.com/?gclid=CM-7qK2ZqIQCFUMGLAodlzm5jA Google Search: faraday + induction Home Depot $19.99 ea. (good price) + ~$6.00 s/h http://www.homedepot.com/prel80/HDUS/EN_US/jsearch/product.jsp?pn=092643 O.K. Text includes numerous misspellings and grammatical errors. http://www.hamuniverse.com/everlifeflashlight.html Google: define: capacitor An electronic device which stores energy and releases it when needed. http://www.flashlightcenter.com/products/batteryless-flashlight.htm -- super size Faraday Flashlight (over 11" long) ***receive two-flashlight combo PLUS super-size: For only $9.95 plus $4.95 S/H, you can Supersize your Faraday Flashlight order.*** http://www.faradayflashlight.com/super.asp http://www.everlifeflashlight.com/super.asp Cricket Productions <-- return address as it appeared on parcels 753 Forest Street Suite 300 FL Marlboro, MA 01752 (508) 449-4299 Faraday Flashlight - AsSeenOnTV.com Official Site http://www.asseenontv.com/prod-pages/everlife_flashlight.html http://www.homedepot.com/prel80/HDUS/EN_US/diy_main/pg_diy.jsp?CNTTYPE= PROD_META&CNTKEY=Products_2%2FSafety+%26+Security%2FFlashlights& ProductOID=680989 Faraday Flashlight Model 100 Price: $19.99/ea "I figure the thing is a coil with a magnet passing through to induce a current with a small transformer to turn the current into a high voltage whose energy is stored in a large electrolytic capacitor. The capacitor is discharged slowly over a resistor and the led/diode in series." http://www.mysimon.com/Flashlights/9000-11032_8-0.html?sdcq= dnatrs-kinetic_dynamo/dfllTrail-Kinetic%20/%20Dynamo http://www.appliedinnotech.com/ NightStar Flashlight The ORIGINAL patented, rechargeable LED flashlight powered by the Faraday Principle! ONLY $39.95 http://shakelight.notanumberinc.com/flashlight/nightstar.shtml also NightStar II Magnetic Flashlight, NightStar CS NightStar Physics Guide Quantity in Basket:none Code: 012 Price:$24.95 http://www.appliedinnotech.com/Merchant2/merchant.mvc?Screen= PROD&Store_Code=AITI&Affiliate=flashlightcenter&Product_Code=012 Diamond Gen III - 20 min. Diamond Gen IV - 2 hr. Shake Flashlight Hummer (brand) Michael Faraday http://www.corrosion-doctors.org/Biographies/FaradayBio.htm "energy chain" chemical --> mechanical (kinetic) --> electrical --> radiant Google Search: "Faraday Flashlight" + physics http://groups.physics.umn.edu/demo/induced_currents.html http://www.phys.unca.edu/ruiz/videos_demonstrations.asp How Things Work Virginia.edu - Electric Power Generation http://rabi.phys.virginia.edu/HTW/electric_power_generation.html How Things Work - Electric Motors http://howthingswork.virginia.edu/electric_motors.html "Explaining the physics of everyday life" search: flashlight [good explanation of basic electricity] -- Google Search: faraday principle Results: Electromagnetic Systems - Basic Operations The Faraday Principle http://www.aqua-data.com/basic.htm <-- features nice graphic of em induction coil The Technology Corner http://www.techexchange.com/thelibrary/techcorner/oct2005/oct2005.html stronger, longer-lasting battery-less flashlights: Diamond LED, Excalibur http://www.techadvice.com/help/Products/B/batteryless-flashlights.asp Google Search: define: galvanometer Electromagnetic Induction http://www.slcc.edu/schools/hum_sci/physics/tutor/2220/em_induction/ == ***GOOD STUFF*** http://regentsprep.org/ http://regentsprep.org/Regents/physics/physics.cfm ***Induction Related Devices*** http://regentsprep.org/Regents/physics/phys03/dinduction/indapart.htm ***Generators*** A generator is nothing more than the reverse (symmetry) of an electric motor. A motor, you put current into it and you get mechanical work out of it. A generator, you put mechanical work into it and you get current out. ***Microphone*** A simple microphone is the reverse (symmetry) of a speaker. A speaker, you put alternating current into it and you get sound out. A microphone, you put sound into and you get alternating current out. >> motor/generator equivalent to speaker/microphone [speaker qua microphone: speaking into the speaker causes spkr. to move back-and-forth, inducing an electric current] ***Loudspeaker*** http://www.kpsec.freeuk.com/components/other.htm#loudspeaker "Loudspeakers are output transducers which convert an electrical signal to sound. ... Miniature loudspeakers can also be used as a ***microphone*** and they work surprisingly well, certainly good enough for speech in an intercom system for example." == First Alert® Eternal Flashlight http://www.improvementscatalog.com/Parent.asp?product=263677x&cm_ven= youramigo&cm_cat=june04&code=macs=MP6SPDR http://www.firstalert.com/Flashlights.aspx Home Depot 7710 Richmond Hwy Alexandria , VA 22306 Phone: (703) 619-5124