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Tuesday 25 December 2012

Lemon Battery


Note : There are many sites on the Internet about the Lemon battery. None of it worked for me. I cracked the simple logic. The below experiment works with 100% success rate. Else comment......I will work on the Experiment again

The lemon battery is a simple type of electrical battery that is commonly made for school science projects because it illustrates a battery's main components. Typically, a piece of zinc metal and a piece of copper metal are inserted into a lemon. Everyday objects such as galvanized nails and copper pennies can be used for the zinc and for the copper. A single lemon is usually studied using an electrical meter. Several lemons can be wired together to form a more powerful battery that will power a light-emitting diode, a buzzer, or a digital clock.

The lemon battery is similar to the first electrical battery invented in 1800 by Alessandro Volta, who used brine (salt water) instead of lemon juice. The lemon battery is described in some textbooks in order to illustrate the type of chemical reaction (oxidation-reduction) that occurs in batteries. The zinc and copper are called the electrodes, and the juice inside the lemon is called the electrolyte. There are many variations of the lemon cell that use different fruits (or liquids) as electrolytes and metals other than zinc and copper as electrodes.

Experiment :

Materials required :

1 . Two to three lemons


















2.    Zinc ( I took it from battery, the silver metal). Open up a battery and u will find a silver colour . Remove the black powder ( carbon) and the carbon rod. You will get the zinc metal



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3.Pure Copper ( copper wire can be got in shops , Its cheap )





First one is a copper vessel which I used it for comfort . The second is the copper wire

4. Connecting wires

   















5. Alligator Clips for Convienence

6. LED ( Light Emiting Diode )  Bulb :

 













7. Switch ( Optional - I never use a switch in my experiment )
 
         Attach it anywhere in the circuit. The negative of the circuit should connect the positive of this switch. The negative of the switch should connect the positive of the circuit.












Connection :


But this wont work....... How many ever times you try it......
So I connected a 1.5 V battery to it. The bulb started glowing....



And yes... You may say that lemon is a conductor of electricity . So the bulb glows . But look at this and try....




That means that the remaining 0.5 V were produced by the Lemons.

Target : Do not use a Battery.

So to make things simple , I take the lemon juice in a Copper Vessel. You can use the same zinc rod and copper rod, but I want to   produce 1.5 V more. Practically it not possible to use 10 to 15 lemons in my experiment.

So I add Harpic (the same cleaner used at home ( Chloric Acid ) ) along with the citric acid.




Reaction :

 When the cell is providing an electrical current through an external circuit, the metallic zinc at the surface of the zinc electrode is dissolving into the solution. Zinc atoms dissolve into the liquid electrolyte as electrically charged ions (Zn2+), leaving 2 negatively charged electrons (e-) behind in the metal:
Zn → Zn2+ + 2e- .

This reaction is called oxidation. While zinc is entering the electrolyte, two positively charged hydrogen ions (H+) from the electrolyte combine with two electrons at the copper electrode's surface and form an uncharged hydrogen molecule (H2):
2H++ 2e- → H2 .

This reaction is called reduction. The electrons used from the copper to form the molecules of hydrogen are made up by an external wire or circuit that connects it to the zinc. The hydrogen molecules formed on the surface of the copper by the reduction reaction ultimately bubble away as hydrogen gas.




This model of the chemical reactions makes several predictions that were examined in experiments published by Jerry Goodisman in 2001. Goodisman notes that numerous recent authors propose chemical reactions for the lemon battery that involve dissolution of the copper electrode into the electrolyte. Goodisman excludes this reaction as being inconsistent with the experiments, and notes that the correct chemistry, which involves the evolution of hydrogen at the copper electrode, has been known for many years.[8] Most of the detailed predictions of the model apply to the battery's voltage that is measured directly by a meter; nothing else is connected to the battery. When the electrolyte was modified by adding zinc sulfate (ZnSO4), the voltage from the cell was reduced as predicted using the Nernst equation for the model. The Nerst equation essentially says how much the voltage drops as more zinc sulfate is added. The addition of copper sulfate (CuSO4) did not affect the voltage. This result is consistent with the fact that copper atoms from the electrode are not involved in the chemical reaction model for the cell.

When the battery is hooked up to an external circuit and a significant electrical current is flowing, the zinc electrode loses mass, as predicted by the zinc oxidation reaction above. Similarly, hydrogen gas evolves as bubbles from the copper electrode. Finally, the voltage from the cell depended upon the acidity of the electrolyte, as measured by its pH; decreasing acidity (and increasing pH) causes the voltage to fall. This effect is also predicted by the Nernst equation; the particular acid that was used (citric, hydrochloric, sulfuric, etc.) doesn't affect the voltage except through the pH value.

The Nernst equation prediction failed for strongly acid electrolytes (pH < 3.4), when the zinc electrode dissolves into the electrolyte even when the battery is not providing any current to a circuit. The two oxidation-reduction reactions listed above only occur when electrical charge can be transported through the external circuit. The additional, open-circuit reaction can be observed by the formation of bubbles at the zinc electrode under open-circuit. This effect ultimately limited the voltage of the cells to 1.0 V near room temperature at the highest levels of acidity.

I will try to make a video for better understanding.

Conclusion:
   Electrical current is the flow of electrons (movement) of an electrical charge and is measured using an ammeter. Solid conductive metals contain large population of free electrons, which are bound to the metal lattice and move around randomly due to thermal energy. When two terminals of a voltage source (battery) are connected via a metal wire, the free electrons of the conductor drift toward the positive terminal, making them the electrical current carrier within the conductor.

Note : If This does not work or you think I am wrong pls don't mind to comment 



Saturday 1 December 2012

Why does a lemon which initially sinks , begin to float ?



Lemon - Sinks first and then Floats. Why ??

Question :

1) Why does a lemon sink in water , initially when dropped and float after sometime ?
2) The weight of the lemon (sink)         = 35 grams
    The weight of the lemon ( floating )  =  45 grams
3) If the weight increases, the lemon should be still sinking. But why is it floating


Conditions for floatation :

  1.  A body floats in water if its density is less than that of the liquid on which it floats
  2. The weight of the object should be less than the weight of the liquid displaced







Solution :         


   The lemon is highly concentrated (hypertonic ) when compared to that of water (hypotonic). It has a density higher than that of water  . Also the weight of the lemon is more than the weight of the water displaced by it. So the lemon sinks as soon it is dropped in water . Due to OSMOSIS , water enters the lemon and brings down its concentration. As a result its density becomes less than that of water. The weight of the lemon becomes less than the weight of the water displaced. Therefore the lemon floats in water.

If you understand the below picture, you yourself will solve this problem :



 

















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Video for better Understanding  :


( Note : If you have a fast internet connection, please view the videos in HD  1080 p for the best clarity . To view it in HD click ' Change quality' and then ' 1080 p ')

My Experiment with Short Explanation of result :



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My Experiment with mathematical proof of result :

( Note : Change the quality for this video also )





With better clarity, I will upload another video .

Other things  noted :

1.      Some lemons readily absorb water and float. While others take hours to number of days.
2.      The presence of some gas ( may be CO2 , not sure) is observed .

Conditions for a body to float :

1.   A less dense body floats over a denser body. (i.e) The density of the floating body is less than the density of water.
2.   The weight of the body must be less than the weight of the water it displaces

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Verification of result through mathematical calculations :

 Step 1 :  Find the weight of water :















Let the weight of the lemon (sink )be                  W1 grams
       The Volume of water displaced be                Vcm3
       The weight of the lemon (float) be               W2 grams
       The Volume of water displace be                   V2 cm3
          Radius of the container ( cylindrical jar )       3.8 cm




















Volume of water displace by lemon ( sink) =     π x 3.8 x 3.8 x 0.7
                                                                 =     31.7552 cm3

Weight of the lemon ( sink )      =    35 grams

Density of lemon ( sink )    =     35 / 31.7552 g cm-3
                                               =     1.102 g cm-3

Volume of water displaced    =  31.7552  cm3

 Weight of water    =  Density of water  x  Volume of water displaced
                                  =  0.995   x  π x 3.8 x 3.8 x 0.7
                                  =  31.5964 grams

Weight of the lemon ( sink ) =  35 grams

Therefore ,   Density of lemon   >   Density of water

                       Weight of lemon    >   Weight of water displaced 

So it sinks in water.
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Volume of water displace by lemon ( float )   =   π  x 3.8  x  3.8  x  0.6
                                                                    =   27.2187  cm3
Density of water         =       0.995 g / cm3

Weight of water displaced   =  Density    x     Volume of water displaced
                                                  =   0.995    x    27.2187
                                                  =   27.0826 grams

Clearly  it is seen that two-fifth of the lemon is above the water.

This means that 

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So , The Density of lemon ( float )   <    Density of water
       The weight of lemon ( float )   <  The weight of water displaced

Therefore the lemon floats in water.

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Now find the weight of full lemon ( the lemon floating in water ) :

Density of lemon =  3 x Density of water
                                     5
Similarly,

 3 ( Weight of lemon ) =  Weight of water displaced
              5

Therefore , the weight of lemon ( the full floating lemon ) =    5 x (Weight of water displaced )
                                                                                                         3
                                                                                     =         5  x  27.0826
                                                                                                         3
                                                                                     =      45.13 grams

 EVEN WHEN THE WEIGHT OF THE LEMON IS INCREASED , IT FLOATS IN WATER BECAUSE IT DENSITY IS LESS THAN THAT OF WATER OR ITS DENSITY IS THREE-FIFTH THE DENSITY OF WATER .

( The Density of this particular lemon, that I have taken is three-fifth the density for water. For every lemon the ratio varies but its density is always less than the density of water )