Fruit Battery
Lesson Plan Amount of time Demo takes:​
(​
3-5​
)
Try this at home!
Materials
1. ​
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Lemons or limes, cut in lengthwise quarters (1-2 lemons, 1 lemon/hr of demos)
Note: other citrus fruit will work - the more acidic the better
2. ​
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Pennies or copper nails (20 total)
3. ​
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Galvanized/zinc-coated nails or screws (20)
4. ​
Light bulb or other low volt, low amp electrical equipment (calculator, digital
clock, etc.) (5 bulbs)
5. ​
​
Multimeter (1)
6. ​
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Copper wire (1 yd)
7. ​
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Knife to cut lemons (1)
8. ​
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Wire cutters (1)
Set up instructions
1. ​
With knife, quarter lemon/fruit lengthwise and cut a slit in the peel to place
penny into. One slice of lemon (or the lemon as a whole) will not create
enough voltage and amps to power the light bulb, but may power a digital
number display such as a calculator or clock.
2. ​
Stick a galvanized nail into the lemon peel. This will be the negative side of
the “battery.” Do this for every lemon in your series.
3. ​
​
In the slit you made in the lemon peel, slide a penny in halfway. This will be
the positive side of the “battery.”
Whether you slice the lemons or leave them whole, this is what the setup should look like
http://www.quantumbalancing.com/images/lembat3.jpg 1/4 4.​
​
Make a series with the lemons and wire: attach the lemons
positive-to-negative to each other, and then to the object you are going to
power. LED lights have both a positive and negative wire coming out of the
bulb. Use the multimeter to find out how many volts you are getting. If you
have less than 1.5 V the light bulb will most likely not light or be very dim. Add
more lemon slices to increase the voltage.
Using multimeter to check voltage
Plug the red cord into V​
Ω​
mA
Plug the black cord into COM
Turn knob left to 2V
Uncap the ends
Place one end on the + side of the battery, one end on the - side.
SAFETY!
1. ​
​
Keep knife out of reach of children.
Lesson’s big idea
●​
​
How do batteries work? ​
The electrons in the piece of fruit will move as
quickly as they can from the negative end to the positive end when a
circuit is completed. Oxidation (the loss of electrons) will happen at
the negative zinc end. Reduction (the gaining of electrons) will happen
at the positive copper end of the battery. As the electrons flow
through this circuit, they will illuminate the light bulb.
●​
​
What is voltage (or, what are volts)? V
​oltage is the name given to an
electric potential difference - the measure of the energy of electricity. It
can be thought of as electromotive force - the difference in electric
potential between two points. Voltage is measured in units called volts.
● What is an amp? ​
Amperes (affectionately referred to as amps) measure
the rate of flow of the electrical charge (current). It is possible to have
enough voltage but not enough amps to power a device. This may be a
limiting factor when you increase the voltage by adding lemons to a
series, but not increasing the rate of flow (this would be sort of like
trying
to add more water to a tank, but not changing anything about the pipe
leading out of it. There would be more water, but no increase in
outward flow).
● Why do we set the lemons up in a series? ​
A single lemon will not produce
2/4 enough volts to light the bulb. By setting up a series, we are able to add
each lemon’s voltage to the total to get a high enough voltage to power
the bulb. When doing this demonstration, use the multimeter to show
the readings for one lemon, two lemons, and so on to show how each
adds to the total in a series.
Instructional Procedure
1. ​
​
Follow set up procedure. If lemons dry out or are not producing enough
energy, use new ones.
2. ​
​
Discuss the vocabulary (voltage, amps, series) to describe how a battery
works and why the lemon is able to power a light bulb.
3.​
​
​
This link​
(hydraulic analogy on Wikipedia) is a helpful analogy to explain the
​
many terms involved when teaching about electricity. It uses a hydraulic
analogy: the “pipes” that carry electricity are the wires, the volume of flow is
the volts, etc. Teaching using an analogy can be extremely helpful because you
are building on someone’s prior knowledge and they will better be able to
follow the new vocabulary as you relate it to that prior knowledge.
4. ​
​
A bit more about volts​
: for simplicity, voltage is always measured between
two points (they may be very close together). Voltage can be caused by static
electric fields, current running through a magnetic field, changing magnetic
fields, or some combination of the three. Electric potential is the measure of
how much energy is required to move a unit of charge to a particular place. We
can measure voltage using a voltmeter.
5. ​
​
A little bit about series and parallel circuits: ​
There are many ways to connect
the components of a circuit. The two most common ways are to do so in series
or in parallel. Connecting elements of a circuit in series simply means to connect
them along a path, one to another in a line. That way, the same current flows
through all the components. That’s what we are doing with the lemons in this
demonstration. The alternative would be connecting in parallel, which allows
“lines/arms” to run parallel to each other and have the same voltage on each
component, but not necessarily the same current.
Assessment/sample questions you can ask
1. ​
​
How does a battery work?
2. ​
​
What is voltage?
3. ​
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What is an electrical series?
4. ​
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Where are some other places that series/parallel circuits are useful in
everyday life?
3/4 Clean Up
Clean up between demonstrations if needed. When completely finished
gather all materials listed for this demonstration and make sure everything is
accounted for. If something was used up, broken or damaged. Let someone
know so it can get replaced or fixed. Wipe down all the equipment to ensure it
lasts as long as possible.
Discard fruit that has been used. Discard corroded equipment (that no longer
will work) and request replacement parts for the kit.
References
http://www.youtube.com/watch?v=AY9qcDCFeVI&feature=r
elmfu​
http://www.howstuffworks.com/battery.htm ​
http://en.wikipedia.org/wiki/Ampere http://en.wikipedia.org/wiki/Voltage http://en.wikipedia.org/wiki/Series_and_parallel_circuits
Next Generation Science Standards
K-4 Content Standard B, Physical Science, Light, heat, electricity and
magnetism
5-8 Content Standard B, Physical Science, Transfer of energy
9-12 Content Standard B, Physical Science, Interactions of energy and matter
4/4