DESIGN AND CONSTRUCTION OF A 6 VOLT LEAD AGD ACCUMULATOR

 

CHAPTER ONE

INTRODUCTION

An electrolytic cells is a liquid that an electric current can pass through especially in an electric cell or a battery.

Electrolytic cell is where current flows from an external power source, the effect of the current that flow is monitored with the help of a galvanometer (G).

Electrochemical cell is one which develops it’s own electromotive force (emf) spontaneously due to a chemical reaction occurring within it, or it can be said that it is used in producing an electric current, setting up two electrodes, which have different potentials. An electric current flows though the wire that connects the two metals or electrodes outside the solution. In an electrochemical cell, chemical energy is converted to electrical energy (eg) batteries. A cell consists of two electrodes placed in an electrolyte.

1.1     STATEMENT OF PROBLEM

At least, without the use of an electrolytic cell most of the work done by machine would have been done by man (e.g) (Lead – Acid Accumulator used to make an automobile function). An electrolytic cells is important in electrochemical industry or electrolysis for the generating of energy, it’s energy will be used up and need to be recharged.

Following the high incidence of importation of electrolytic or cost of production in our country, it is very important that small-scale industries with particular reference to battery production should be encouraged. One way of doing this lies heavily on local manufactures of the raw materials needed by these industries.

AIM AND OBJECTIVE OF THE PROJECT

This work is designed to provide basic experience in the choice of preparation, handling and the use of electrodes and to explain it working principles. To illustrate the relevant application, off different electrochemical cell. To be able to prepare an electrolyte used to generate electric current.

LIMITATION OF STUDY

This research work is limited only to the construction of an electrolytic cell, where by chemical energy is used to generate electrical energy. (E.g) Lead – Acid Accumulator used by automobiles.

WORKING PRINCIPLE F A CELL

The secondary cell processes an internal resistance due to which some voltage is lost in the form of potential difference drop across it, when current flows. Hence the internal resistance of the cell has to be kept to the minimum. To insurance size of the plates, there is a limit because at right it is too big to be handled. In practice it is usually to multiple the number of plates inside the cell and to join all the negative and the positive plates together. The effect is equivalent in joining many cell in parallel. At the same, time, in side the cell a current must also flow, replenishing the electrons lost from the zinc plate as they flow away toward the copper plate round the external circuit.

There must be a force causing those current to flow. The electrons current round the external circuit and the other current through the internal circuit of the cell. This force is called the electromotive force (emf) generated by the cell. Since current flow between two points due to a potential difference, the force is measured in the same unit as a potential difference (pid) namely in volts.

When the cell is working, the passage of the current causes a liberation of energy in producing a heating effect and so on. The evolution of hydrogen and the gradual dissolution of the zinc plate show that the current is accompanied by chemical reactions. Chemical energy is being used up and electrical energy appears in its place subsequently being turned to heat, that this sort of process can eventually produce the heat. The heat produced is shown by the pouring some dilute sulphuric acid on a lump of granulated zinc in a beaker. A cell has its own capacity.

ELECTROCHEMISTRY

Is concerned with the properties of solution of electrolytes and with processes that occur at the electrodes. Then a useful starting points is provided by farady’s law of electrolysis and also other theories like Arrheinus which considered how this associates with equilibrium shift as a concentration of the electrolyte is varied on weak and strong electrolyte and also Debye and Huckel, worked on the distribution of positive and negative ion in solution as a result of electrostatic force.

Nernst equation shows how the cell (emf) varies with concentration of solution in the cell. It explain about the concentration of cell that is obtained by connecting two hydrogen electrodes by means of a saltbridge, the redox cell since when cell operates there is an electron transfer at the electrodes oxidation and reduction are occurring.

1.6     THERMODYNAMICS OF ELECTROCHEMICAL CELL

During the last century, studies were made of the relationship between the emf of a cell and the thermodynamics of a chemical reactions occurring in the cell. These studies, made an important contributions to the understanding of the basic principles of thermodynamics. An early contribution was made by Joule who, with very simple apparatus but with accurate temperature and current measurements, found in 1840 state that, the calorific effects of equal quantities of transmitted electricity are proportional to the resistance opposed to it’s passage, whatever may be the length, thickness, shape or kind of metal which closes the circuit ad also that caeteris paribus, these effect are in the duplicate ratio of the quantities of transmitted electricity and consequently, in the duplicate ratio of the velocity of transmission. In Taile’s conclusion, it stated that the heat generated in a wire is (IVT) is quite correct, but latter he and other went wrong. In 1852 he concluded that there is a correspondence between the heat of reaction of a cell and the electrical work. This error was also made by Helmholtz and William Thomson. Thomson’s conclusion appeared to be supported by his calculation of the emf of the Daniell cell from the heat of the reaction, his valve, 1.074V, is practically the measured valve, but this agreement is accidental.

It remained for Willard Gibbs to draw the correct conclusion, in 1878, that the work done in an electrochemical cell is equal to the decrease in what is now known as the Gibbs energy.

1.7     ELECTROMOTIVE FORCE (EMF)

When a simple cell is first made, a potential difference is obtained when a voltmet is connected across the plates. This is due to electrical action between the copper and acid and between zinc and acid. The net effect is a potential difference between copper and zinc with copper at a higher potential than zinc.

The name electromotive force is given to the maximum potential difference between the terminals of a cell when rid resistance is connected to it. It is considered a force inside the cell which maintains the electric current in the wire.

But we define electromotive force (emf) in terms of energy because the cell is a source of energy. The electromotive force is a total energy per coulomb obtainable from the cell.

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