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ES Lesson 3: Batteries • What is a battery? • How does a battery work? • Let’s make one. © 2012 C. Rightmyer, Licensed under The MIT OSI License, 20 July 2012 ES demo 3-1. Use a battery as the electron generator Luigi Galvani’s accidental discovery [Electricity & Magnetism, Adamczyk & Law, Usborne Publishing, 1993] The world’s first battery: the Voltaic pile electrolyte disk zinc copper http://simple.wikipedia.org/wiki/Voltaic_pile G. Stevens, Electricity and Magnetism Electrode potential relative to hydrogen Sodium Aluminum Tin Zinc Iron Nickel Hydrogen Copper Silver Platinum Gold Mercury Na Al Sn Zn Fe Ni H Cu Ag Pt Au Hg 2.71 1.66 0.14 0.8 0.44 0.25 0 -0.34 -0.8 -1.2 -1.43 -0.8 [Intro to College Physics, Appleton-Century-Crofts, R.D. Rusk, 1960] [http://labspace.open.ac.uk/file.php/5259/T357_1_ie001i.jpg] ES project 3-2. Half of us build a single cell battery using Volta’s choice of electrodes (copper and zinc). 0.5 Vdc Vdc - zinc washer + copper washer cotton ball dipped in brine ES project 3-3. The other half will use aluminum and copper for electrodes. 0.6 Vdc Vdc - + aluminum washer cotton ball dipped in brine copper washer ES project 3-4. Put two like type batteries together in series 1.2 Vdc Vdc - + Getting more voltage by adding batteries in series (+) 6 volts, 5 amps 1.5 volts, 5 amps (-) http://electronics.howstuffworks.com/everyday-tech/battery.htm 6 volt, 5 amp lightbulb ES demo 3-5. Measure the voltage and current required to turn on an LED. ma LED vdc + 9v + Symbol for LED 50k pot Notes: (1) LED’s require about 1.5 to 1.7 volts to begin operation. (2) Brightly lit LEDs consume about 12 milliamps . Hookup diagram for ES demo 3-5 BE ckt 2-10 ma vdc + 9.0 Longer lead of LED goes to the top (+). volts 50K W pot Expected about 1.8 volts and 5 to 8 ma for bright LED operation. Getting more current by adding batteries in parallel (+) 1.5 volts, 20 amps 1.5 volts, 5 amps 1.5 volt, 20 amp lightbulb (-) http://electronics.howstuffworks.com/everyday-tech/battery.htm ES project 3-6. Make a lemon battery using copper and zinc electrodes zinc coated nail (cathode) copper nail http://www.monkeysee.com/play/6352-how-to-make-a-battery Measure the lemon battery’s voltage 0.9 v Vdc + Light Emitting Diode (LED) Adapted from http://www.kpsec.freeuk.com/components/diode.htm ES project 3-7. Connect two lemon batteries in series for twice the voltage (~ 1.8 Vdc) Red LED requires ~ 1.8 v and ~ 5 mA current. http://www.monkeysee.com/play/6352-how-to-make-a-battery ES project 3-8. Connect two in-series lemon batteries in parallel for twice the current ES demo 3-9. Assemble a film-canister battery using copper and zinc electrodes with vinegar as the electrolyte. BE demo 1-8 ?? Vdc Vdc zinc nail (cathode) copper coil (anode) Bobtail squid with its fluorescent capable bacteria while hunting on a moonlit night http://www.smithsonianmag.com/specialsections/40th-anniversary/Listening-to-Bacteria.html?c=y&page=5# Picture of the “Christmas” Octopus ES L3 background slides http://www.monkeysee.com/play/6358-how-to-power-a-stopwatch-with-a-homemade-battery What’s needed to make a battery? Electron flow Conventional current _ cathode - + - ELECTRONS + + + - + + + - - + + + + + + anode IONS electrolyte • Two dissimilar metal electrodes (such as zinc and copper) • An electrolyte solution (such as vinegar) One type dry inexpensive dry cell battery. ammonium chloride & manganese dioxide Chemical reactions for a carbon-zinc battery Zn (s) + 2 MnO2 +2 NH4Cl +(aq) --> Mn2O3(s) + Zn(NH3)2 The part of the equation after --> represents the electrical part of what is happening in the battery. The manganese dioxide (Mn2O3) molecuses have absorbed one electron each thereby making them positively charged. The zinc has combined with the the ammonium compound (NH3) and has lost two hydrogen electrons, thereby offering up two electrons to the cathode. These electrons are capable of providing electron flow from the battery’s cathode to anode. Here’s how we make the batteries. coiled copper wire (anode) Zinc plated or aluminum nail (cathode) http://www.monkeysee.com/play/6352-how-to-make-a-battery Wind coil around pen using 12 inches of 20-gauge copper wire http://www.monkeysee.com/play/6352-how-to-make-a-battery Demonstrate making a potato-battery Zinc coated nail (cathode) - + http://www.monkeysee.com/play/6352-how-to-make-a-battery Copper nail (anode) Measure the potato-battery voltage ~ 0.6 volts DC VOM red lead VOM black lead - + Volt_Ohm_Meter (VOM) set on DC volts Potato juice is the electrolyte (phosphoric acid) http://www.monkeysee.com/play/6352-how-to-make-a-battery Three potato-batteries hooked in series 1.8 v Vdc - + Three batteries illuminate the LED but not brightly LED on but not bright. (Need more current) Red LED requires ~ 1.8 v and ~ 5 mA current. LED’s long lead goes to + - + Two sets of 1.8 volt potato batteries in parallel LED shines brightly! - + - +