Hilaroad:
Red lead from multimeter connects to positive (+) terminal of battery; 
black connects to negative (-) terminal. For a Cu/Zn electrode pair, Cu is 
the positive terminal.

A multimeter also has two wires, one red (+) and one black (-), with metal 
tips. They are called probes.

> > Use red & black Sharpies to mark positive (red) & negative
(black) terminals on analog volt- and amp meters.

electrons flow out negative terminal of battery; in positive terminal

==
Note: Two or more interconnected PV modules create an array.
> Wire solar panels in series; test to see if there is enough
current to "power" flashlight bulb.
YES! Photovoltaic cells rated for 0.5 V. [see sidebar notes, below]

[mount solar panels on ring stand using test tube clamps]
Five (5) solar panels = 2.5 V.
(-)red[]black --> red[]black --> red[]black --> red[]black(+) Where: [] =
solar panel

==
Now for some history: The Daniell Cell is named for John Frederic
Daniell (1790-1845) who was an English chemist and physicist noted
for electrical and meteorological investigations. The cell named
after him was used in telegraphy and furnished 1.08 volt. It
consisted of an amalgamated zinc electrode in dilute sulfuric acid
(1:12 dilution of concentrated acid) and a copper electrode in
saturated copper sulfate solution. In more recent time, any galvanic
cell using the reaction: Zn + Cu++ --> Zn++ + Cu is called a Daniell
cell. The two electrodes are separated by a porous partition that
permits diffusion of ions between them.

The cell that I demonstrate is close to the "Daniell
Cell," but it does not have the porous partition between the
electrodes. Similar to the original cell demonstrated by Daniell, it
depends on the difference in densities of the Zn solution (0.01M) and
Cu solution (1.0M) and is called a "Gravity Cell"! End of history
lesson.

Dave

[Addenda: WBS]
Cell Container: 250 mL beaker
Electrolyte Solutions: CuSO4 (bottom); ZnSO4 (top)
Electrode Pair: copper (bottom); zinc (top)
Conducting Pathway: Vernier voltage probe + laptop/LCD; LED & buzzer 
(requires two cells wired in series)

Set-up:
Add ZnSO4 first (~100 mL, or enough to cover copper electrode); use small 
glass funnel (with cotton plug insert in order to enable slow flow of 
liquid) to add CuSO4 to bottom of beaker (enough to cover copper 
electrode, thereby raising liquid boundary layer midway between electrodes 
and also covering zinc electrode).

Pre-Demo Demo:
Insert copper electrode into ZnSO4; no reaction. Insert copper electrode 
into CuSO4; no reaction. Insert zinc electrode into ZnSO4; no reaction. 
Insert zinc electrode into CuSO4; zinc electrode is quickly plated with 
copper. If this happened in a battery, then the battery would quickly "go 
dead" because you would end up with two copper electrodes, which students 
should know will have no voltage potential.

Main Demo Point(s) of Focus:
> Difference in density enables one liquid to "float" on top of the other;
> "Gravity Cell" clearly demonstrates (in clear glass beaker) what we are 
unable to observe through the opaque lemon peel -- the migration of ions 
in solution in the electrolyte!

Post-Demo P.O.D.: Draw and label the essential parts of the "Gravity Cell" 
battery. Which electrode is positive; negative? (Need to know in order to 
trace flow of electrons along conducting pathway.) Copper ions migrate 
(diffuse) upward into zinc sulfate solution; at least 12 hours before 
class, set-up a third cell used to illustrate this point.

==
[misc. notes re: solar cell array]

Subject: Solar Cell (fwd) [23 JAN 2007]
[the following info printed on plastic packaging]
[FCPS?] CAT#WL2148M-02
UM:EA
SOLAR CELL .5V 500MA 3X1-7/8IN VEN# 3-500

==
4-cell array, ~6" away from 150- to 200 W light bulb:
+2.015 V (measured with Vernier Voltage Probe)
40 D.C. mA current (Google Calculator: 40 milliamperes = 0.04 amperes)

In direct sunlight, solar array generated ~2.0 V and ~300 D.C. milliamps 
of current (0.3 A) [enough to power flashlight battery]

==
Subject: Testing Circuits with a Multimeter - Show Direction of Electron 
Flow

http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA8/SampleUseOfMovies/CJM/
8_01_7_6_C_00_1a_.html

A multimeter and a battery are used to show how positive and negative 
multimeter readings indicate the direction of electron current in a 
circuit.

Discussion

A digital multimeter can be used to determine the direction in which 
electrons move in an electrical circuit. Current and voltage readings are 
positive when electrons move from the negative multimeter jack through the 
multimeter to the positive multimeter jack.

An AA battery has a (+) mark on the end that is positively charged and a 
(-) mark on the negative end. When the positive end and negative ends of 
the battery are connected through an electrical circuit, electrons move 
through the circuit from the negative end of the battery to the positive 
end.

In this movie the multimeter is set to read DC voltage. When the red 
(positive) lead is connected to the positive jack of the multimeter and 
the positive end of the battery, and the black (negative) lead is 
connected to the negative jack of the multimeter and the negative end of 
the battery, the meter reading is positive -- electrons are moving through 
the multimeter from the negative jack to the positive jack. When the 
connections to the battery (but not to the multimeter) are reversed, the 
reading is negative -- the direction of electron flow is reversed.

In the same way, when the multimeter is set to read current, a positive 
reading means electrons are moving through the multimeter from the 
negative jack to the positive jack, and a negative reading means electrons 
are moving in the opposite direction.

==
Subject: GE (Flash)Light Bulbs

GE 222 (Flash)Light Bulbs

2.25V .25A/TL-3 Mini Screw Base

Light Bulb Manufactured by: Eiko
SKU 40492
Brand Eiko
Volts 2.25
Base Miniature Screw
Bulb TL-3
Filament C-2R
Average Life (hours) 5
Boxed & Bulk Miniature Lamps
MOD (Diameter) 0.38in/9.6mm

==
> I ordered the Radio Shack multimeter. Is the red probe always positive and
> the black negative? Can I use the multimeter and red & black Sharpies to
> label the connectors on our analog volt- and amp meters so that the kids
> connect the test leads correctly (w/o having to reverse them)? If so, then
> how can I be sure I've labeled the terminals properly (Sharpies are
> permanent markers!)? Specific guidance is sincerely appreciated!

By convention, red is used for positive and black for negative. There's no 
difference at all between the probes electrically, of course. I presume 
the connectors on your existing meters are already labeled (but not 
color-coded), are they not? [Note: SMS analog volt- and amp meters are NOT 
labeled.] If not, the easiest way to figure it out is to use a battery to 
figure out the polarity, then mark the connectors appropriately.
Phil Wherry