Battery lemon is a simple battery that is often made for educational purposes. Usually, a piece of zinc metal (such as galvanized spikes) and a piece of copper (like a penny) are inserted into the lemon and connected by cable. The power generated by the metal reaction is used to light a small device such as a light-emitting diode (LED).
The lemon battery is similar to the first electric battery found in 1800 by Alessandro Volta, which uses salt water (salt water) instead of lemon juice. The lemon battery describes the type of chemical reaction (oxidation-reduction) that occurs in the battery. Zinc and copper are called electrodes, and the juice in the lemon is called an electrolyte. There are many variations of lemon cells that use different fruits (or liquids) as electrolytes and metals other than zinc and copper as electrodes.
Video Lemon battery
Use in school project
There are many sets of instructions for making lemon batteries and for obtaining components such as light-emitting diodes (LEDs), power meters (multimeters), and zinc-coated (galvanized) nails and screws. The commercial "potato clock" science kit includes electrodes and low voltage digital clocks. After one cell is assembled, a multimeter can be used to measure the voltage or electric current of a voltaic cell; the typical voltage is 0.9 V with the lemon. The current is more variable, but ranges up to about 1 mA (the larger the electrode surface, the larger the current). For more visible effects, the lemon cells can be connected in series to turn on the LED (see illustration) or other devices. Series connection increases the available voltage for the device. Swartling and Morgan have published a list of low-voltage devices along with the number of lemon cells needed to move them; they include LEDs, piezeoelectric buzzers, and small digital clocks. With zinc/copper electrodes, at least two lemon cells are required for all these devices. Changing the magnesium electrode to the zinc electrode makes the cell with a larger voltage (1.5-1.6 V), and a single magnesium/copper cell will drive multiple devices. Note that the incandescent light bulb of the flashlight is not used because the lemon battery is not designed to produce enough electric current to turn it on. By multiplying the average flow of lemons (0.001A/1mA) with the average (lowest) voltage (potential difference) of the lemon (0.7V), we can conclude that it takes more than 6 million lemons to give us the car battery power of 4320W average.
Variations
Many fruits and liquids can be used for acidic electrolytes. The fruit is comfortable, as it gives electrolytes and a simple way to support the electrode. The acids involved in citrus fruits (lemons, oranges, grapefruits, etc.) are citric acid. The acidity, as measured by pH, varies substantially.
Potatoes have phosphoric acid and work well; they are the basis for a commercial "potato clock" kit. Battery potatoes with LED lights have been proposed for use in poor countries or by populations outside the network. International research began in 2010 showing that boiling potatoes for eight minutes increased their electrical output, as did placing potato wedges between several copper plates and zinc. The boiled and chopped bananas (stems) are also suitable, according to Sri Lankan researchers.
Instead of fruit, liquids in various containers can be used. Household vinegar (acetic acid) works well. Sauerkraut (lactic acid) is featured in an episode of the US television program Head Rush (a branch of the MythBusters program). Sauerkraut has been canned, and becomes an electrolyte while the tin itself is one of the electrodes.
Zinc and copper electrodes are quite safe and easy to obtain. Other metals such as lead, iron, magnesium, etc., can be studied as well; they produce different voltages of zinc/copper pairs. In particular, magnesium/copper cells can produce a voltage of 1.6 V in a lemon cell. This voltage is greater than can be obtained using zinc/copper cells. This is comparable to a standard household battery (1.5 V), which is useful in powering the device with a single cell rather than using cells in series.
Learning outcomes
For the youngest disciple, around the age of 5-9, the purpose of education is utilitarian: the battery is a device that can drive other devices, provided they are connected by conductive materials. Batteries are components in electrical circuits; hooking a single cable between the battery and the bulb will not turn on the light bulb.
For children in the 10-13 age range, batteries are used to describe the relationship between chemistry and electricity as well as to deepen the circuit concept for electricity. The fact that different chemical elements such as copper and zinc are used can be placed in a larger context that the elements are not lost or damaged when they undergo chemical reactions.
For older students and for students, batteries serve to illustrate the principle of oxidation reduction reactions. Students can find that two identical electrodes do not produce voltage, and that different metal pairs (outside of copper and zinc) produce different voltages. The voltage and current of the circuit and the parallel combination of batteries can be checked.
The current released by the battery through the meter will depend on the size of the electrode, how far the electrodes are inserted into the fruits, and how close to each other the electrodes are placed; voltage is quite independent of the details of this electrode.
Maps Lemon battery
Chemistry
Most textbooks present the following model for the chemical reactions of a lemon battery. When the cell provides an electric current through an external circuit, the metal zinc at the surface of the zinc electrode dissolves into the solution. The zinc atoms dissolve into the electrolyte liquid as electrically charged ions (Zn 2 ), leaving 2 negatively charged electrons (e - ) behind in the metal:
- Zn -> Zn 2 2e - .
This reaction is called oxidation. While zinc enters the electrolyte, two positively charged hydrogen ions (H ) of the electrolyte join the two electrons in the copper surface of the electrode and form a charged hydrogen molecule (H 2 ):
- 2H 2e - -> H 2 .
This reaction is called reduction. The electrons used from copper to form hydrogen molecules are transferred by an external wire connected to zinc. The hydrogen molecules that form on the copper surface by the reduction reaction end up bubbling as hydrogen gas.
Experiment results
This chemical reaction model made several predictions examined in an experiment published by Jerry Goodisman in 2001. Goodisman notes that many authors have recently proposed chemical reactions to a lemon battery that involves the dissolution of the copper electrode to the electrolyte. Goodisman excludes this reaction as inconsistent with the experiment, and notes that true chemistry, which involves the evolution of hydrogen in copper electrodes but also can use silver instead of copper, has been known for years. Most of the detailed predictions of the model apply to a battery voltage measured directly by one meter; nothing is connected to the battery. When the electrolyte is modified by adding zinc sulfate (ZnSO 4 ), the voltage of the cell is reduced as estimated using the Nernst equation for the model. The Nernst equation basically says how much voltage goes down because more zinc sulfate is added. Addition of copper sulfate (CuSO 4 ) does not affect the voltage. This result is consistent with the fact that the copper atoms of the electrodes are not involved in the chemical reaction model for the cell.
When the battery is connected to an external circuit and a significant electric current flows, the zinc electrode loses mass, as predicted by the above zinc oxidation reaction. Similarly, hydrogen gas evolves as a bubble of copper electrodes. Finally, the voltage of the cell depends on the acidity of the electrolyte, as measured by its pH; decreasing the acidity (and increasing the pH) causes the voltage drops. This effect is also predicted by the Nernst equation; The specific acids used (citrate, hydrochloric, sulfur, etc.) do not affect the voltage except through the pH value.
The Nernst equation prediction fails for a strong acidic electrolyte (pH & lt; 3.4), when the zinc electrode dissolves into the electrolyte even when the battery does not give current to the circuit. The two oxidation reduction reactions listed above only occur when the electrical charge can be transported through an external circuit. Additional open-circuit reaction can be observed by bubble formation on the zinc electrode under open circuit. This effect eventually limits the cell's voltage to 1.0 V to near room temperature at the highest acidity level.
Energy source
Energy comes from chemical changes in zinc when it dissolves into acids. Energy does not come from lemons or potatoes. Zinc oxidizes in lemons, exchanging some of its electrons with acids to reach a lower energy state, and the released energy provides strength.
In practice today, zinc is produced by electrowinning zinc sulfate or pyrometallurgical reduction of zinc with carbon, which requires energy input. The energy generated in the lemon battery comes from reversing this reaction, recovering part of the energy input during zinc production.
Smee cell
From 1840 to the end of the 19th century, large voltaic cells using zinc electrodes and sulfuric acid electrolytes were widely used in the printing industry. While copper electrodes such as those in lemon batteries are sometimes used, in 1840 Alfred Smee discovered a refined version of this cell that uses silver with a coarse platinum layer rather than a copper electrode. Hydrogen gas attached to the surface of a silver or copper electrode reduces the electric current drawn from the cell; This phenomenon is called "polarization". Rough surfaces, "platinized" accelerate bubbles of hydrogen gas, and increase the flow of cells. Unlike zinc electrodes, silver or platinized copper electrodes are not consumed by battery, and the details of these electrodes do not affect the voltage of the cell. Smee cells are convenient for electrotyping, which produces copper plates to print newspapers and books, as well as sculptures and other metal objects.
Smee cells use combined zinc instead of pure zinc; The surface of amalgamated zinc has been treated with mercury. It turns out that the combined zinc is less susceptible to degradation by acidic solutions than pure zinc. Zinc zinc and zinc electrode basically provide the same voltage when pure zinc. With imperfect zinc in 19th century laboratories, they usually provide different voltages.
In popular culture
- In the video game Portal 2 , GLaDOS antagonists are embedded into a potato-operated computer for an important part of the game. In The Season 6 episode "The Proton Resurgence", Leonard and Sheldon's childhood hero, Professor Proton (Bob Newhart) tries to show the group of potato batteries, which surprises Penny.
- In Season 6's episode "The Blackout in the Blizzard", Angela and the other "squint" build an array of giant potato batteries in an attempt to power up the phone. Describing the low output of such a system, it works in just a few seconds while using dozens of potatoes. In the "Lemon" episode of the Red Dwarf television program (the tenth series (X Series)), the crew traveled 4,000 miles from England to India on 23 AD to get lemons to build lemon batteries for turn on remote machine of their time.
- In the last sixth episode of the Mystery Science Theater 3000 season, the main villain Pearl Forrester tried to take over the world using a potato battery, only to be ruined by Professor Bobo.
- In NCIS Season 7 episode 8, "Power Down", Abby Sciuto uses lemons as a resource for her voice when she runs out of battery when there is a power outage.
- In Terry Pratchett and Stephen Baxter The Long Earth (series), devices used to move from one universe to another seem to be powered by a potato battery.
See also
- List of battery types
- Alessandro Volta
- Electrochemical cell
- Galvanic cells
- Galvanic Corrosion
- Lasagna cells
- Penny Batteries
References
Further reading
- "Maglab - Simple Electric Selection Tutorial". US National High Magnetic Field Laboratory . Retrieved 2012-11-30 . Ã, Description of the acid cell with zinc & amp; copper electrodes, including JAVA based animation. Animation shows zinc dissolves into electrolytes, electrons flowing from zinc to copper electrodes, and small hydrogen bubbles coming out of copper electrodes. Animation also shows that one cell can turn on the LED, which is not possible for LEDs that emit visible light.
- Margles, Samantha (2011). "Does the Lemon Battery Really Work?". Book of Mythbusters Science Fair . Scientific. pp.Ã, 104-108. ISBNÃ, 9780545237451 . Retrieved 2012-10-07 . Ã, Just an online preview.
External links
- Lemon Battery Video. The cool and fun animated video explains in great detail how the lemon battery works from the inside.
- An orange battery video. An orange battery powered a cheap digital watch.
- Potato battery video on YouTube. Three potato cells in the power circuit of the calculator.
Source of the article : Wikipedia
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