Pangunahon nga Pagbuhat ug Pagsulay sa Voltaic Cell

Isipadong voltaic cell mahimo kung isulob ang usa ka zinc plate ug usa ka copper plate sa sulod sa tubig nga gilubog sa sulfuric acid solution. As shown in the figure, if the copper plate and zinc plate are connected externally with an electrical load, an kuryente magsugyot gikan sa copper plate hangtod sa zinc plate pinaagi sa load. Kini nagpasabot na mayroon ngadto sa pagitan sa copper plate ug zinc plate. Tungod kay ang kuryente magsugyot gikan sa copper hangtod sa zinc, obvious nga ang copper plate magiging positibong nahargahan ug ang zinc plate negatibong nahargahan.

Pagtrabaho sa Voltaic Cell

Ang prinsipyong pagtrabaho sa voltaic cell depende sa prinsipyo nga kapila duha ka dissimilar metals gisulob sa sulod sa electrolyte solution, ang mas reaktibo nga metal magtendensiya mopasok sa electrolyte ingon positive metal ions, nag-iwan og electrons sa metal plate. Kini nagresulta sa mas reaktibo nga metal plate negatibong nahargahan.

Ang less reactive metal mag-attract sa positive ions sa electrolyte, ug hain ang positive ions magdeposito sa plate, nagresulta sa plate nga positibong nahargahan. Sa kasong simple voltaic cell, ang zinc mogawas sa sulfuric acid solution ingon positive ion, ug reaksiyun sa negative SO4 − − ion sa solution ug form zinc sulfate (ZnSO4). Tungod kay ang copper mas less reactive metal, ang positive hydrogen ions sa sulfuric acid solution magtendensiya mopasok sa copper plate. Mas daghan zinc ions mogawas sa solution, mas daghan electrons mag-iwan sa zinc plate. Ang mga electrons magsugyot pinaagi sa external conductor giconnect sa zinc ug copper plates.

Pag-abot sa copper plate, ang electrons mocombine sa hydrogen atoms deposited sa plate ug form neutral hydrogen atoms. Ang atoms mocombine sa pairs para form molecules of hydrogen gas ug ang gas lastly mogawas along the copper plate ingon hydrogen bubbles. Ang chemical action taking place inside the voltaic cell is as follows,

However, this action stops when the contact potential between Zn and dilute sulfuric acid reaches the value of 0.62 Volt. During operation of a voltaic cell, the zinc late is at a lower potential with respect of the solution film adjacent to it as shown in the figure below.

Ganahan, when Cu plate is placed in contact with the electrolyte, then the positive hydrogen ions in the solution have a tendency to get deposited on it until its potential rises nearly to 0.46 V above that solution. Hence, the electrical potential difference developed in a voltaic cell is 0.62 − (− 0.46) = 1.08 Volts.

In a simple voltaic cell there are mainly two drawbacks, referred as polarization and local action.

Polarization sa Voltaic Cell

It is observed that in this cell, the current gradually gets reduced and after a certain time of its operation, the current may cease altogether. This decrease in current is due to the deposition of hydrogen on the copper plate. Although the hydrogen comes out from the cell in form of bubbles, still there is a formation of a thin layer of hydrogen on the plate surface. This layer acts as an electrical insulation, thereby increase the internal resistance of the cell. Because of this insulating layer, further hydrogen ions cannot get electrons from the copper plate and get deposited in ion form. This layer of positive hydrogen ions on the copper plate exerts a repulsive force on other hydrogen ions which are approaching the copper plate. Hence the current gets reduced. This phenomenon is known as polarization.

Local Action sa Voltaic Cell

Nahitabo nga even when the voltaic cell is not supplying any current, zinc continuously gets dissolved in the electrolyte. This is due to the fact that some traces of impurities like iron and lead in commercial zinc form tiny local cells which are short-circuited by the main body of zinc. The action of these parasitic cells cannot be controlled so that there is some wastage of zinc. This phenomenon is known as local action.

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