 What we need for the construction of electrochemicals is we need two halves to take one Z-electrode and the other one is copper. Which one acts at an odd and which one acts at the upper? Z for copper. Z is an odd. What is the electro potential of Z? Minus 2.76 and for copper it is 0.34. So the more electro potential, the reduction will be easier. That is what we are following. So when you take zinc and copper, zinc will behave as anode and that is why zinc we have to write the zinc electrode or zinc arc cell or anodic arc cell we always write on the left side. So this is zinc electrode or zinc rod we can see. So in zinc rod we are taking what is the electrolyte here. The electrolyte must contain Zn plus 2i. That is the condition of half cell. The metal must be placed in the solution of its own ion. So in zinc rod we are taking Zn plus 2i. The solution must be what? Zn plus 4. In the solution must contain Zn plus 2i. That is the constant we have. Similarly here we have copper electrode. This is copper rod and the electrolyte is what? Electrolyte must contain Cu plus 2i. So electrolyte we are taking here is aqueous Cu as of. So after some time what happens? Since it is anode half cell we have. So there is oxidation takes place. So Zn will convert into Zn plus 2 aqueous and releases to electron. This is Zn solvents. So this rod becomes what? Negatively charged because Zn plus 2 is coming into the solution. So in the solution the concentration of Zn plus 2i increases. Initially what happens when we have Zn as before initially present? The concentration of Zn plus 2 is equals to the concentration of as of 4 2 minus. The solution is neutron initial. But when the reaction when you dip this electrode into this solution and this electrode releases Zn plus 2i. So obviously the concentration of Zn plus 2i in the solution increases. So now the solution is not electrically complex. It is positively charged. Similarly here what happens? Copper Cu plus 2 in this solution takes to electron. This is copper aqueous and converts into Cu solvents. This Cu plus ion deposited onto the electrode and the rod becomes what? Positive electron. When you connect this electrode, this two electrode is an external source of external wire conducting wire. Then there will be what? The current flows from negative rod to positive rod. So the direction of currents will be what? From anode to this is anode. And this is cathode. We always write or draw anode half-silver in the electron side. It is the convention. So this direction represents what? The flow of electrons. Because the negative electron has more electrons. Obviously the electron flows from negative rod to positive rod. So what is the direction of current then? Current flows in opposite direction. The direction of electron is anode to cathode right now. The direction of electron from anode to cathode. You can also write it as from negative rod to positive rod okay. The direction of current will be reversed from cathode to anode. This question also they ask. And the instruction of electrochemicals and then I will ask many times for example this is also important. Thanks. Now what happens? Initially the current starts flowing in this two electrode but the circuit is not connected. These two are connected but the circuit is not connected right. This is one reason why after some time the cell stops working okay. For second reason is what? When this rod is negatively charged around this rod what we have? Positive charge. This positive charge I will grind here to make you understand. When this question they ask in example don't cross this positive charge okay. So this positive charge because this positive charge this will drag the electrode from this electrode right. And similarly here the solution becomes what? Negative charge right. And this negative charge will also reveal the electron that is coming from this electrode to that electricity right. So after some time what happens? The flow of electron will be difficult right. And hence the cell stops working. The electron does not flow and hence the current also reveals right. So this is the drawback or this was the problem initially with the electrochemicals. Now to overcome this like problem what we use? We use a u shaped inverted u and this we call it as what? Salt bridge. Salt bridge is what? It is a u shaped inverted u in which there is some electrolyte present in semi liquid form or semi solid form right. Now in this electrolyte you can use many different electrolyte kc l l s for l s v. Suppose I am using kc l here kc l is k plus and c l minus. Remember this end is open and it is not close. This end is also open and it is not close right. Now electrolyte if you are using a salt bridge it is in semi liquid form. It cannot flow right. Like you can see the best, best material kind of thing is there. So whenever what is the purpose of this? Whenever one positive charge develops over here right. If we neutralize this positive charge and this negative charge then the neutrality of these two half cells will be maintained and the electron can be basically flow. Now the purpose is to work to neutralize this positive and negative charge. And for that purpose we are using this sort of bridge in which the electrolyte is present right. So whenever one positive charge forms into this particular half cell and already half cell the c l minus moves from this u shaped tube and comes into the solution and will neutralize this positive charge over here. So this negative charge will neutralize this positive charge and hence this positive charge will also go there and neutralize this negative charge into this half cell right. So when the charge we get neutralized it means the electrical neutrality will be maintained and hence the current continues. Understand this. This is the purpose of solid bridge right. There are two three conditions for the electrolyte we use in solid bridge for this such that. Because two things which is important in our real construction of electro chemical cell is important. They specifically ask this question also what is the function and importance of solid bridge in that cell right. So this is the diagram of electro chemical cell. Now you see this is anode right. Since it is present on the left side we call it as left half cell and what present on the left side we call it as left half cell right. Actually I know what happens oxidation takes place. So we also call it as what oxidation half cell. Since it is anode hence we also call it as anode half cell or anode half cell right. Anode is negatively charged so we also call it as what negative half cell. All these are same things. All these names are same okay. So you have to analyze this. So how do you analyze and you have to analyze this particular graph right. Left half cell oxidation takes place. Where oxidation takes place we call it as anode half cell and anode half cell is negative. Just reverse of this will be what? The other one right. So it is left so it is right half cell, reduction half cell, cathode half cell and positive half cell. Just reverse of this. So when you keep this in mind at all here reverse of that will be what? The cathode. So we done this right on next. In the construction of electrochemical cell, oxidation half cell, oxidation half cell is always placed oxidation half cell is always placed on the left side on the left side. Reaction we have written no reaction of anode reaction okay. One more thing we mentioned here since this red and solid is converting because red is plus 2 at first. So weight of this rod will decrease or increase? Decrease. Decrease. So weight of anode rod decreases. Similarly here the copper is leaving the positive electrode. So weight of cathode rod increases. Next we make out. There is salt rich expulsion and impotence. Salt rich expulsion and impotence. And inverted u shaped cube, u shaped cube which contains and inert electrolyte, inert electrolyte, ACS and H4CL, H4CL etc. In agar agar we mix this in this powder to make it semi liquid. In agar agar powder in practice right now in semi liquid state. The end of salt rich is open. Salt rich is open so that the ions of electrolyte can move easily into the house. Complete the circuit by maintaining the flow of electron. The electrical neutrality of the solution changes the electrical neutrality of the solution. Minimizes the liquid-liquid junction potential. Minimizes the liquid-liquid junction potential. This potential you see is negative and positive charge. Since this positive charge is getting into light this difference potential difference is getting minimized.