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Make electricity from a lemon (or
potato)
Electricity can also be made
by a chemical reaction. This method is used in batteries and
creates direct current (DC). Here is a sample recipe of making
electricity in chemical way. Material that you need for this
experiment are:
- Citrus fruit
(lemons or limes
work best)
- Copper electrode about 5 cm
long
- Zinc electrode about 5 cm
long
- One small light bulb (1.3
volts)
- Socket for light bulb
- Wires
- Alligator clips
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Step by step instructions:
| Note:
The instructions below suggests to cut certain lengths of
insulated wire and then remove the insulation from the ends. If
you are using connection wires with alligator clips in both
ends, you don't have to cut the wire and remove the insulation.
Use alligator clips for all connections. |
1. Roll the fruit under the
palm of your hand to soften but be careful you don't break the
skin. Work it gently on a piece of scrap paper or a paper towel. (If you
are using potato, skip this step)
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2. Mount your bulb socket (base)
on the board, cut about 1.5 feet wire and carefully remove the
insulation of about 1" on each end of your wires.
3. Connect one end of each
wire to an alligator clip and the other end to the bulb socket.
4. Screw the bulb and use a
small AA size battery to test your bulb. (To do this connect
alligator clips to the poles of your battery, light bulb should
lit.)
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5. Insert the electrodes into
the fruit about 5 cm apart. Don't allow the electrodes to go through
the bottom skin of the fruit. If your electrodes are large sheets,
cut as much as you need. Also electrodes should not touch each other.
6. Connect DC volt meter to the
electrodes, it should show some voltage. If you see some voltage,
connect alligator clips
to the electrodes to see if you get some light!
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Important notes:
- If you just use a Voltmeter
to show the electricity, you get a better result because small
amount of electricity can simply move the needle of a volt-meter,
but can not turn on a light bulb.
- More metal surface in contact
with the fruit will result in more electricity. Since the produced electricity
is so little, you have little chance on turning on a light bulb, but
you can definitely show the produced voltage using a multi-meter
and you can use that electricity to turn on a digital clock or
small digital calculator, because these two need much less electricity
than a bulb.
Investigate the probability of using other fruits and vegetables
to make electricity. Measure the pH of each "battery"
and see if there is a relationship between the pH of the juice
and the amount of light that is produced. If you have a multi
meter, you can measure the voltage and current produced.
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In this sample we are using
a copper sulfate solution as an electrolyte (plus a few drops
of sulfuric acid). One electrode is copper and the other is zinc.
It created 0.9 volts electricity that was able to turn on a 1.2
volts light bulb for about 1 minute.. |
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Light up an LED
| L.E.D. or Light Emitting
Diode is an electronic light source that needs less electrical
current to light up. Use of LEDs instead of miniature light bulbs is
recommended by ScienceProject.com because with LEDs, students will
have a better chance to get a visible light in their experiments. |
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Low
voltage LEDs are included in your kit
Although LEDs do not require
much current, they need a minimum voltage of about 3 volts.
| Each fruit battery
usually creates about one volt. To get a higher voltage you will
have to connect 2 or more fruit batteries in series. To do that, you
use alligator clip wire leads to connect the copper (+) electrode of
one battery to the Zinc (-) electrode of the next battery. At the
end, you will connect the LED to the Zinc electrode of the first
battery and copper electrode of the last battery.
We used (+) and (-) above just to
remind you that copper is always the positive electrode and zinc is
the negative electrode. |
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Identifying the polarity or
direction of electricity is especially important when you are trying to
light up an LED.
Each LED has 2 legs. One is
longer than the other. The longer leg must be connected to the positive
pole of the battery or copper. The shorter leg must be connected to the
negative electrode or Zinc.
If you don't have enough
copper and zinc electrodes, you may cut your existing electrodes in half
and make 2 electrodes form one; however, remember that electrodes cannot
be very small. The surface contact of the electrodes with the fruit must
be as much as possible in order to get the most electric current.
| LEDs require more
than 2 volts to light up. Picture in the right shows 3 potato
batteries connected in series so they can produce about 2.2
volts and light up an LED.
LEDs do not require much
current, so it is possible to cut electrodes in half and use
them to make more fruit batteries. |
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| Although the picture
is not clear enough, in this battery a total of 6 electrodes are
used. First the large potato is sliced and then electrodes and
slices are placed next to each other from left to right:
Potato - Zinc - Potato - Copper
- Zinc - Potato - Copper - Zinc - Potato - Copper - Potato.
The first Zinc is connected to
the short leg of LED. The last copper is connected to the
long leg of LED. |
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Make Electricity from Copper Sulfate Electrolyte
For this experiment we decided
to use copper sulfate as electrolyte because copper sulfate is
available @ ChemicalStore.com. You can also get copper and zinc
electrodes from MiniScience.com.
If you could not find zinc, just get a galvanized iron. It does
the same thing in a few seconds until the layer of zinc is destroyed.
You will need to add a few drops of sulfuric acid for the process
to speed up and turn on the light. Sulfuric acid also is known
as battery acid and can be purchased from auto parts store. You
need diluted sulfuric acid (about 5 to 10%). Acid sulfuric is
very corrosive and you must have gloves, goggles and protecting
clothing while handling it.
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Material needed are:
- 2 plastic or ceramic cup
- 2 sheets of copper (2"
x 4")
- 2 sheets of zinc (2"
x 4")
- 50 grams copper sulfate
- 10 cc Sulfuric Acid 10%
- One 1.2 Volts bulb with socket
- Three wires (with alligator
clips if possible)
- One Multi-meter (Set to Voltage)
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In the first experiment,
secure a copper plate and a zinc plate on the sides of the cup
as your electrodes. As the picture shows you can bend the sheet
toward outside. Use two wires to connect the electrodes to the
light bulb holder and screw the bulb. Temporarily remove the
zinc plate and then fill up the cup with copper sulfate solution.
Now insert the zinc electrode.
Although the process starts and electricity is being produced,
the light bulb may still be off. Add a few drops of sulfuric
acid to expedite the process and get some light. To stop the
process remove the zinc plate. If you want to test the voltage,
make sure you unscrew the bulb first. |
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This process will release
hydrogen that is hazardous and breathing that will cause choking. So
do the experiment in a well ventilated place and avoid keeping
your head right above the cup.
This chemical reaction creates
about 0.7 volts that is barely light up a 1.2 Volts bulb. But
is not able to light up a 2.5 volts bulb that is shown in this
picture. |
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In the next experiment
we connected two cups together as shown in the picture. That
created about 1.2 volts and produced a small light on our 2.5
volts bulb.
Now you know why I insist on
low voltage bulb for this test. |
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This picture shows the bulb
in the last experiment. |
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Testing other electrolytes such
as salt water and lemon juice produced much less electricity
and no lights at all. |
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We decided to repeat
the first experiment with 5 small cups and smaller pieces of
copper and zinc plated screw instead of zinc.
Multi-meter showed that each
cup is producing 0.7 volts and 5 cups together produced 2.3 volts. |
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Even though we had 2.3 volts
of electricity, it could not turn on the light. The reason is
that small electrodes can not create enough electric current. |
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Latest Update: (Make a Sandwich)
| This new experiment
using copper sulfate produced a long lasting bright light.
Procedure:
Make about 30 mL saturated
solution of Copper Sulfate. |
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| Cut 2 pieces of felt
about 1/2" smaller than your copper and zinc plates both in
length and width.
Place one copper electrode on the
table and connect it to one side of the light bulb. |
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| Insert one piece of
felt in saturated copper sulfate and place it on the center of the
copper plate.
Place a zinc plate over the felt.
Place another copper plate over
the zinc plate. |
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| Insert another felt in
copper sulfate and then place it on the center of the top copper
plate.
Finally place another zinc on the
top and connect that to the other side of the light bulb. You
should get the light. |
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* Notes:
- Felt should get wet, but it should
not have any excess liquid running off the felt.
- You may substitute the felt with any
thick, absorbent cotton fabric.
- Copper Sulfate is not included in
your kit, but it may be purchased from hardware stores and pool
chemical suppliers.
- As a result of this experiment, a
layer of black copper oxide will be formed on the zinc as shown on
the above picture.
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