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 G. Stevens, Electricity and Magnetism zinc copper electrolyte disk

Electrode potential relative to hydrogen [Intro to College Physics, Appleton-Century-Crofts, R.D. Rusk, 1960] [

ES project 3-2. Half of us build a single cell battery using Volta’s choice of electrodes (copper and zinc). zinc washer copper washer cotton ball dipped in brine 0.5 Vdc Vdc + -

ES project 3-3. The other half will use aluminum and copper for electrodes. aluminum washer copper washer cotton ball dipped in brine 0.6 Vdc Vdc + -

ES project 3-4. Put two like type batteries together in series 1.2 Vdc Vdc + -

Getting more voltage by adding batteries in series volts, 5 amps ( + ) ( - ) 6 volts, 5 amps 6 volt, 5 amp lightbulb

Symbol for LED ES demo 3-5. Measure the voltage and current required to turn on an LED. LED ma Notes: (1) One 9 volt battery. (2) LED’s require from 1.7 to 2 volts for operation. (3) Measure the minimium current and voltage for LED operation. Symbol for variable resistor + - pot 100 ohm 50k pot 9 v +

Hookup diagram for ES demo 3-5 :10 vdc Longer lead of LED goes to the left (+). 100 vdc Expected about 1.8 volts and 5 to 8 ma for bright LED operation. 50K  pot volts ma

Getting more current by adding batteries in parallel volts, 5 amps ( + ) ( - ) 1.5 volts, 20 amps 1.5 volt, 20 amp lightbulb

ES project 3-6. Make a lemon battery using copper and zinc electrodes zinc coated nail (cathode) copper nail

Measure the lemon battery’s voltage 0.9 v Vdc + -

Light Emitting Diode (LED) Adapted from

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.

ES project 3-8. Connect two in-series lemon batteries in parallel for twice the current

?? Vdc Vdc zinc nail (cathode) copper coil (anode) ES demo 3-9. Assemble a film-canister battery using copper and zinc electrodes with vinegar as the electrolyte.

Bobtail squid with its fluorescent capable bacteria while hunting on a moonlit night

Picture of the “Christmas” Octopus

ES L3 background slides

What’s needed to make a battery? Two dissimilar metal electrodes (such as zinc and copper) An electrolyte solution (such as vinegar) anode cathode ELECTRONS IONS Conventional currentElectron flow + _ electrolyte

One type dry inexpensive dry cell battery. ammonium chloride & manganese dioxide

Chemical reactions for a carbon-zinc battery Zn (s) + 2 MnO 2 +2 NH 4 Cl +(aq) --> Mn 2 O 3 (s) + Zn(NH 3 ) 2 The part of the equation after --> represents the electrical part of what is happening in the battery. The manganese dioxide (Mn 2 O 3 ) 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. Zinc plated or aluminum nail (cathode) coiled copper wire (anode)

Wind coil around pen using 12 inches of 20-gauge copper wire

Demonstrate making a potato-battery +- Copper nail (anode) Zinc coated nail (cathode)

Measure the potato-battery voltage VOM red lead VOM black lead Volt_Ohm_Meter (VOM) set on DC volts ~ 0.6 volts DC Potato juice is the electrolyte (phosphoric acid) + -

+ - Three potato-batteries hooked in series 1.8 v Vdc

Three batteries illuminate the LED but not brightly + - Red LED requires ~ 1.8 v and ~ 5 mA current. LED on but not bright. (Need more current) LED’s long lead goes to +

Two sets of 1.8 volt potato batteries in parallel LED shines brightly!