Download JA-645 Lesson 10

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!
-
+
-
+