Measuring the Voltage of Fruits

In Glogpedia

by Andrewzhen
Last updated 6 years ago

Energy & Environment

Toggle fullscreen Print glog
Measuring the Voltage of Fruits


-Using a multimeter, you can measure AC voltage, DC voltage, resistance, and electrical current. In my case, I am using DC current because I am measuring a "battery." -An AAA battery measures 1.5 volts, while an AA battery also measures 1.5 volts. One fresh Granny Smith apple or lemon could almost produce as much voltage as an AAA battery. -The penny is the cathode (positive) while the galvanized nail is the anode (negative). -In our homes today, we use AC voltage because it is a safer alternative to DC voltage. Thomas Edison wanted to use DC voltage, but was beat out by Nikola Tesla, who supported AC voltage. -Today's pennies do not have as much pure copper as they used to. -Builders like to use galvanized nails because the zinc that covers the nail helps protect the nail, as it offers water resistence and helps prevent cracks. -Granny Smith apples aren't part of the citrus family, but are high in acidity. -You could also use liquids that are high in acid, such as vinegar, and conduct and experiment similar to this one. -Potatos can also produce electricity because they contain phosphoric acid, which can also serve as an electrolyte. -The chemical reaction that creates the electricity is called oxidation-reduction.

-two (2) boxes Alligator Clips -two (2) Galvanized Nails -two (2) copper pennies -one (1) multimeter (to measure voltage)-one (1) timer

Voltage of Fruits

Testable Question


What did I do?



Materials Used

My Hypothesis

What I think will happen

The fresh lemons, and the fresh Granny Smith apples both measured at about 1.2 volts. I then measured the voltage of an AA battery, I was surprised to find that an AA battery only clocks in at 1.5 volts. That means that one of these fruits could produce almost enough voltage to match that of an AA battery! After 30 minutes, the lemon is completely dead in terms of voltage, while the apple still has voltage, but is slowly, but steadily decreasing in voltage. After one week in the fridge (note these are different lemons and oranges), there seems to be a big change in the voltage of the lemon, but not the apple. It seems like time does affect the voltage of fruit, so the answer to my testable question is yes. Check out the graphs to the right! The blue points represent what the voltage of the lemon was after a certain time, while the red line represents the voltage of the Granny Smith apple after a certain time. In the graphs to the right, I also drew a "trendline" for both fruits in the two graphs. A trendline, also known as the line of best fit, approximates the rate of change in your data. The X axis, also known as the independent variable, represents the time in minutes. Meanwhile, the Y axis, or the dependent variable, represents the voltage of the two fruits I tested.

The first part of my exeriment was to research and buy materials. (see Materials Used) I then tested the voltage of a lemon by putting a penny into one side of the lemon, and putting a galvanized nail into the other. I used the alligator clips, and clipped them onto the penny and the nail. The last step is to connect the multimeter. The multimeter has two different wires, the negative wire, and the positive wire. I tried connecting the positive wire to the nail, and when that didn't work, I connected the positive wire to the penny, and the dial of the multimeter shot right up. Then, I tested whether time would affect the voltage of the fruits. I got out my trusty timer and measured how long each fruit took until it ran out of voltage. I then left the bag of the Granny Smith apples, and the bag of the lemons in the refrigerator for a week each. After a week, I took out a different lemon, and a different apple, and measured their voltage.

Measuring the

Will time affect the voltage of fruit?


What happened?

ConclusionWhy did it happen?

I hypothesized that the voltages of the lemons and the apples would remain similar when kept in the refrigerator. The results from the graph suggest that my hypothesis is partially correct, because the voltage the apple produced remained steady after a week in the refrigerator, while the lemon lost much of its voltage. In both of the graphs, the blue dots represent the voltage of the lemon at a certain time, while the red dots represnt the apple I tested at a certain time. In the first graph, the voltages of the lemon and apple were measured over a 30' period, and the same experiment was repeated a week later. In both times, the voltage produced by apple declined slowly whereas those of the lemons dramatically decreased. Also noteworthy, the lemon produced less voltage after being kept in the fridge for a week. Why is that? It is because the lemons will dry up in the refrigerator as there is very little protecting the juice. This together with the damages sustained by the nails and pennies could also explain the quick loss of voltage once I started the experiment. Meanwhile, apples have a hard inside, which helps prevent the juice inside from drying up.


AbstractSome facts about my investigation

Did You Know That?The process of these fruits creating an electrical current is actually quite simple. The battery, which consists of the galvanized nail, penny, and the fruit (that is high in acidity) is actually called a voltaic battery, or a voltaic pile. A voltaic battery changes chemical energy to electrical energy. The nail and the penny are called electrodes, which are the positive and negative sides of a battery. The acid inside the fruit is called the elctrolyte, electrolytes can carry electricity, but the fruit itself cannot produce electricity. But with the help of two metals, copper, and zinc, you can make a battery. The galvanized nail has a zinc coating, and as the zinc dissolves in the electrolyte of the fruit, the chemical reaction called oxidation reduction occurs. Electrons from the nail flow into the acid of the fruit, while electrons from the acid of the fruit flows into the copper. Therefore completing the circuit.

A huge limitation I had was that the fresh Granny Smith apples' voltage took too long to run out. I eventually stopped the experiment when it had been 30 minutes and the voltage still wasn't at zero. Another limitation is that the multimeter I used was an old analog one, unlike today's digital multimeters, the one I used was not accurate to the nearest hundreths of a volt.


Table of Fresh Fruit

Table of One Week Old Fruit in Refrigerator

Data and Observations

As I was measuring the voltage of the two fruits, I noticed that no matter what side of the fruit the penny was on, it was always the positive of the battery. Meanwhile, the nail was always the negative. I also observed that when I connected the positive wire of the multimeter, to the nail, the dial of the multimeter would go backwards. The same can be said for when I connect the negative wire of the multimeter to the penny.

If lemons and apples are both kept fresh in the refrigerator for a certain amount of time, the voltage they produce will remain steady.


    There are no comments for this Glog.