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制作一个海水电池

2018-4-22 10:13| 发布者: dymodel| 查看: 230| 评论: 0|原作者: hog

摘要: 大家在论坛内都已经看到过海水电池,但海水电池到底怎么做呢?相信很多朋友还是不太清楚的,下边我就把这个海水电池的制作实验分享给大家,希望这个海水电池的制作能给大家以启发。 An experimental sea sea-wate ...
大家在论坛内都已经看到过海水电池,但海水电池到底怎么做呢?相信很多朋友还是不太清楚的,下边我就把这个海水电池的制作实验分享给大家,希望这个海水电池的制作能给大家以启发。

An experimental sea sea-water battery
We have seen how a pair of electrodes can produce a voltage when immersed in an electrolyte. In the following experiments we use of galvanised (zinc- plated) screws and carbon rods as the electrodes and salt water as the electrolyte. While carbon is a good conductor of electricity, the chemistry that takes place at the carbon electrode is more complicated than would be the case when simply using metals. However, larger potentials are produced with carbon and zinc than with copper and zinc, so it is worth the complication. Carbon is a good conductor of electricity. In these cells the metal (zinc) electrode is negative (-) while the carbon becomes positive (+).
To get round the limited voltage and current of such a simple cell, we can join up cells to make a battery of cells - thereby increasing the power. An effective arrangement is shown in the diagram Figure 1. Household ice- cube trays are used to hold the electrolyte, and wood supports the multiple pairs of electrodes, a set for each ice cube tray.
Making the battery
Each of the ice cube trays is 3/4 filled with a salt solution (sea water or a solution of table salt in water). Galvanised screws can be purchased from any hardware store. Pencil leads can be used for the carbon rods or, better still, they can be salvaged from carefully dismantled old ('flat') batteries. Then the electrode pairs are lowered into their respective ice cube tray soluti** to create the 12 cells. They are then wired-up on the top side of the wooden support to form the battery.

Wiring the the cells up in series or parallel?
So what is the best way to wire up the 12 cells to get useful power from the battery? C**ider a single cell; it can produce a voltage of V volts and a maximum current of say I amps. Wiring a number (n) of these cells in series (one after the other in a sort of daisy chain) will multiply the voltage giving n x V volts. However, the maximum current produced by this arrangement will be the same as that of a single cell - I. On the other hand wiring all the cells in parallel will increase the curent n-fold but maintain the voltage equivalent to that of a single cell (i.e. V). Combinati** of series and parallel cells with produce combination of possible total V and I. 
The ice cube tray used in these experiments had 12 compartments (ice cubes) and so to get useful power from the battery two combinati** of wiring were chosen (see Figure 2): The first a) c**ists of two sets of six cells wired in series and these two sets then wired in parallel - giving a total of 6 x V and 2 x I. b) c**isted of two sets of six parallel parallel cells which were wired in series - giving a total of 2 x V and 6 x I. 

Figure 1. two of the many possible circuit arrangements for making a battery from 12 sea water cells 
Parts list:
Table 1) Salt (NaCl)
2) Ice- cube trays
3) Wood for electrode support
4) galvanised screws ( ca. 5 cm long) for each battery
5) 12 pencil leads (2B or softer), or better still, school lab carbon rods or ones salvaged from old worn out batteries
6) Tinned copper wire

Figure 2. The multiple pairs of electrodes are shown attached to the wooden support. This is the 'high' voltage, 'low' current version. The ice cube trays hold the electrolyte for each cell. The cells are wired up above the board. 
A sea water power plant (!)
The first battery circuit provides a relatively higher voltage than the second and so it can therefore be used to power devises devices that need 'higher voltages' but low currents. A pocket LCD calculator, an LED (and series resistor), and possibly a pocket radio, will work well using this arrangement. In the dem**trati** we use a simple flashing LED circuit to dramatically show the battery working. This circuit requires about 3V, but only about 1 or 2 mA to work. 
Please Note: remember to check that the device you are powering is correctly wired to the

The obvious places for further experimentation are to try different electrode materials (what is the effect of the surface area of the electrodes for example) and try using different electrolytes (for example try orange juice, vinegar, sulphuric sulfuric acid, or even urine!). Does the current produced from the battery simply depend on electrolyte concentration or does it fail at some threshold value? What is the effect of the temperature of the electrolyte in the cells and if so why does it have an effect? Does this help to explain why you can rejuvenate used batteries by putting them on a warm radiator? 
If you want the battery to start to work (to be activated) when immersed in sea water then try putting small pieces of sponge between the electrodes. When the empty battery is immersed, the sponges soak up sea water so that electrolyte remains between the electrodes when the battery is taken out. (If you leave the contraption in the sea many of the cells would be shorted out by the sea water - hence you need to take the battery out of the sea after the water gets in). This was the way we made the emergency life jacket lights in the fifth series of Rough Science set in Zanzibar (BBC2 Feb. 2005). When the life jacket went into the sea it activated the battery, powering the emergency lights. 
The Baghdad Battery
In 1800 Count Alessandro Volta made what was thought to be the first device that we can c**ider as a modern day battery. He found from experiments that different metals in contact with each other via salt solution soaked strips created electricity. He made a device composed of an alternating pile of metal coins sandwiched between electrolyte (salt water) moistened felt strips. Connection to the two end of the pile allowed access to the voltage. This device became known as a 'voltaic pile' (historically this is where the terms volt and voltages got there names). In their modern form batteries are a recent invention although of course voltages have been present since the elements were formed and electrolytes could form and also in creatures such as electric eels etc. But was Volta's pile the first battery? There is however a rather controversial theory that batteries might have been around for more than 2000 years! 

Figure 4. Schematic of the 200 BC Baghdad Battery composed of a ceramic pot, a copper cylinder, iron rod and vinegar electrolyte

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