Thanks, guys.
I gave up at 0530 as I was close to dropping!
Went to bed and got up at 0620!!!
I have made cells with acids, alkalis and saline solutions. They all work to varying degrees.
Graham, I'm using BZP screws, which seem to work quite well.
On the look out for long zinc coated clout nails, they should be better?
Here is the revised texts. "Strictly speaking" notwithstanding, can anybody else see a major flaw with my text?
Cells And Batteries.
In the modern age we all rely heavily on batteries: they run everything from clocks and watches to mobile phones and MP3 players and cars and commercial vehicles, to name but a few.
Who invented the battery?
The first electrochemical cell was developed by the Italian physicist Alessandro Volta in 1792, and in 1800, he invented the first battery. He gave his name to the volt, the unit of electrical force.
Strictly speaking, a battery is a collection of multiple electrochemical cells, but the term "battery" is often used to describe a single cell.
How do they work?
A simple cell (or battery) works by using two dissimilar metals (the electrodes) immersed in a paste or liquid (the electrolyte) that is either acidic or alkaline or a saline solution (salt and water mixed together).
This starts an electrochemical reaction where ions flow through the electrolyte and (when equipment is connected to the cell or battery) electrons flow through the wires. The voltage produced is largely dependent upon the type of metals used.
Power from food.
Do you think we can use some fruit to run a clock? Or some potatoes to turn a fan?
It seems hard to believe, but foods can be used like batteries to provide power to run electrical items.
In this experiment, we will build food cells and batteries.
When we have successfully built and tested a battery for voltage, we will connect it up to a piece of equipment to see if we can really use food as batteries!
The experiment.
We will use a copper nail as the positive terminal of the cell (the cathode), and a zinc plated screw as the negative terminal of the cell (the anode).
These electrodes will be inserted into the food or immersed in the liquid .When using citrus fruit, roll the fruit gently but firmly on the tabletop. This will release the fruit’s juices. Do not apply too much force or the fruit will split and become useless. It is important to make sure these electrodes are a similar distance apart in each food. We can then test the cell for voltage, then vary the distance between the electrodes and test again.
After preparing several cells, we will then link them together to make a battery and test them to see what voltage they produce.
EXPERIMENT RESULTS
Name:.................................................................
Patrol:.................................................................
Write down here the answers to the following questions:
What were the voltages/ pH values of the following:
a single lemon cell?................................................ a single orange cell?..............................................
a single apple cell?................................................ a single potato cell?...............................................
a single cola cell?.................................................. a single saline solution cell?..................................
In terms of voltage, did it make a difference how far apart the two electrodes are? If so, why?
........................................................................................................................................................
What was the minimum number of cells needed to power the clock?..........................................
...to power the 5 volt fan?..............................................................................................
...to power the 12 volt fan?................................................................................................
Conclusions:
The conclusions I have jotted down are:
To note the relation between pH value & cell voltages.
If the electrodes are further apart, the cell voltage drops.
Saline is neither acid nor alkaline.
More cells are needed for higher voltage devices.
