Sci Blog entries

As everybody knows electricity is one of the most needed stuff we need in daily life, we can't afford to not having it.It allows our television,computer,washing machine and refrigerator to work. Abuses of electricity often result in fire, so must handle it in care.If you burn a material like paper using electricity with high voltage,it will sure burn it.Have you ever tried to heat a fruit with electricity(high voltage)? Below is a video on electricity.








There is also another video about electricity, but this time it relates to battery. As everybody know,there must be battery so that a circuit will set up. But do you think lemon can replace battery as "battery"? The following video will review your answer.





The aim of this experiment is to show students how batteries work. After the battery is assembled, a multimeter can be used to check the generated voltage. In order for a more visible effect to be produced, a few lemon cells connected in series can be used to power a standard LED. Flashlight bulbs are generally not used because the lemon battery cannot produce the amount of current required to light such bulbs. Digital clocks can work well, and some toymakers offer small kits with a clock that can be powered by two potatoes or lemons.

The energy for the battery does not come from the lemon or potato, but rather the energy comes from the chemical change in the zinc. The zinc is oxidized inside the lemon, exchanging some of its electrons in order to reach a lower energy state, and the energy released provides the power. The lemon or potato merely provides an environment where this can happen, but they are not used up in the process.






Creating a battery from a lemon is a common project in many science text books. Successfully creating one of these devices is not easy.
Batteries consist of two different metals suspended in an acidic solution. Copper and Zinc work well as the metals and the citric acid content of a lemon will provide the acidic solution.
Batteries like this will not be able to run a motor or energize most light bulbs. It is possible to produce a dim glow from an LED.
The picture at the top of this page shows a basic lemon battery, a lemon, copper penny and zinc coated nail.
The lemon: A large, fresh, "juicy" lemon works best.
The nail: Galvanized nails are coated in zinc. I used a 2" galvanized common nail.
The penny: Any copper coin will work. (Canadian pennies from 1960 - 2001 all worked)





Creating the battery: Insert a penny into a cut on one side of the lemon. Push a galvanized nail into the other side of the lemon. The nail and penny must not touch
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This is a single cell of a battery. The zinc nail and the copper penny are called electrodes. The lemon juice is called electrolyte.
All batteries have a "+" and "-" terminal. Electric current is a flow of atomic particles called electrons. Certain materials, called conductors, allow electrons to flow through them. Most metals (copper, iron) are good conductors of electricity. Electrons will flow from the "-" electrode of a battery, through a conductor, towards the "+" electrode of a battery. Volts (voltage) is a measure of the force moving the electrons. (High voltage is dangerous!)






I have connected a volt meter to our single cell lemon battery. The meter tells us this lemon battery is creating a voltage of 0.906 volts.
Unfortunately this battery will not produce enough current (flowing electrons) to light a bulb.







To solve this problem we can combine battery cells to create higher voltages. Building more lemon batteries and connecting them with a metal wire from "+" to "-" adds the voltage from each cell.




The two lemon batteries above combine to produce a voltage of 1.788 volts. This combination still does not create enough current to light a small bulb. Note the red wire connecting the batteries is joined from "+" (penny) to "-" (galvanized nail).




Four lemon batteries create a voltage of 3.50 volts. We should be able to light up a small device like an LED (Light Emitting Diode).
Note the connecting wires go from "+" to "-" on each battery.




LED
To turn on an LED you must determine the "+" and "-" connections. If you look closely at the red plastic base of an LED you will notice a "flat" spot (indicated by arrow above). The wire that comes out beside the flat spot must connect to the "-" side of a battery, the other wire to the "+" side.

Important information about LEDs: LEDs are designed to work at very low voltages (~ 2V) and low currents. They will be damaged if connected to batteries rated at over 2 volts. LEDs require resistors to control current when used with batteries rated at over 2 volts. Lemon batteries produce low current. It is OK to connect an LED to a lemon battery.





In the above image, electrons flow from the "-" (nail) end of our lemon battery through the LED (making it glow) then back to the "+" (penny) end of the battery. This is an electronic circuit. The LED glows dimly with this configuration.




Improving your battery.
The quality of the copper and zinc can be a problem for a battery like this. Pennies in particular are rarely pure copper.
Try substituting a length of 14 gauge copper wire (common house wire) for the penny. Experiment with different lengths and configurations of electrodes. Other sources of zinc and copper may be found in the plumbing supply department of a hardware store.










LIM WEI BIN(26) 2E3
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