7/31/2019 ELEM HZILAG

1/2

A home-madebatteryElectric voltage, including that from a battery,is expressedin volts and, indeed, this measure is derivedfrom the name of Alessandro Volta, an Italianphysicistwho lived from 1745 to 1827. Volta continuedtoresearch galvanic electricity made by hiscompatriotand colleague Luigi Galvani (who was amedical doctoras well) in 1780 and built the fi rst battery in1800: theVoltaic pile. The pile originally consisted of

30, andlater of 70, silver and zinc plates separatedwith clothsoaked in a salt solution. Volta himself calledthe constructionan electromotor.We build a variant based on the batteryprinciple: wereplace soaked cloth with a glass of water inwhich saltand sodium carbonate are dissolved andsubstitutealuminium and copper for the silver and zincplates.

The advantage of the glass of water is thatwe can putin small copper or silver objects (jewellery)which aremiraculously cleaned, but more about thatlater. Sinceone glass results in a voltage of only 1.15volts, we immediatelystart with two glasses, so that with 2.3 voltswe can demonstrate the operation of thehome-madebattery straight away with an illuminatedLED.Here is the recipe for the liquid in each glass:- 1 teaspoon of table salt (available from thesupermarket);- 1 teaspoon of sodium carbonate (availablefromthe same supermarket or from the chemist);- as much water as fi ts in a glass of about200 ml(available from the tap).Stir the solution thoroughly so that the saltand sodiumcarbonate are completely dissolved.In this solution we now hang a strip ofaluminium foilwith a width of about 4 cm and about 15 cmlong. The

easiest way is to fold the end around the topof theglass and hold it in place with a rubber band.

Now we strip a piece of fl exible copper wire(mainsfl ex) of the same length and hang it in thesolution inthe same way. Make sure that the copper andaluminiumdo not touch each other, otherwise our

batterybecomes short-circuited. If necessary, use apaper clipto press the foil to the inside of the glass.

The battery is now fi nished. Between thestrip of aluminiumand the piece of copper wire there is now anopen-circuit voltage of about 1.15 volts, thecopper isthe positive terminal and the aluminium isthe negativeterminal.As already mentioned, we make a secondbattery in

the same way and connect it in series withthe fi rst: thecopper wire of one glass is connected withthe aluminiumfoil of the other glass (making this connectionusing copper wire does not matter). Solderingthe wireto the aluminium will not work; clamp thestripped endof the connecting wire under the rubber bandagainstthe aluminium foil. We now have two freebatteryterminals: an aluminium terminal (the

negative of thetwo-cell battery) and the copper terminal (thepositive).Between these two terminals there is anopencircuitvoltage of 2.3 volts, which we use to power ared (high-effi ciency) LED. Connect, with ashort lengthof wire, the short terminal of the LED (=cathode) tothe aluminium negative terminal (clampunder the rubberband) and the long terminal (= anode) to thecopper

positive terminal. (When connecting the LEDthereis an easy to remember rule: the short or cutterminalis the cathode.) If you inadvertently connectthe LEDthe wrong way around there is no danger ofdamage the voltage is too low for that.After the LED has been on for a while andtherefore thebattery has been used for some time, you willnoticethat the copper is nice and clean. This home-made batteryis therefore eminently suitable for thecleaning of

7/31/2019 ELEM HZILAG

2/2

copper or silver.We omit the LED as well as the copperpositive terminal.Now we will not load the battery (one glass isenough) externally, but internally! The insideof theglass is now completely covered with

aluminium foiland the copper or silver objects to be cleaned(whichnow function as internal negative terminals)are placedin the solution in such a way that they justtouch thefoil on the side (an internal short-circuittherefore).After a while they are as new! This is becausean extremelythin layer is etched away from the outersurface.So dont forget to remove your clean silver

jewellery,because after a while you may get theimpression thata theft has occurred, without any traces ofburglary...