Lemon or potato battery
Zinc nails and copper wire pushed into lemons make a battery that lights an LED.
The big idea
A battery stores energy as chemicals. When the chemicals react, they release electricity. A lemon makes a simple chemical cell.
You will need
Tick things off as you gather them.
Step by step
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Step 1: Soften the lemons
Roll each lemon firmly on a table. This breaks the inside so the juice flows freely.
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Step 2: Push in the metals
Push a zinc nail and a piece of copper wire into each lemon, about 3 to 4 cm apart. They must not touch each other inside.
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Step 3: Join them in a chain
Use a wire to connect the copper in lemon 1 to the zinc nail in lemon 2. Then copper in lemon 2 to zinc in lemon 3. Keep going to the end.
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Step 4: Connect the LED
Connect the free copper at one end of the chain to the long leg of the LED. Connect the free nail at the other end to the short leg.
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Step 5: Look closely
Dim the room lights. The LED should glow faintly. If it does not, check that each metal is pushed in firmly and the legs are the right way round.
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Step 6: Measure the voltage
If you have a multimeter, measure one lemon, then two joined, then three. Note how the voltage grows.
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Step 7: Try other fruit
Swap in a potato, an orange or a tomato. Which gives the strongest glow?
What to look for
- One lemon is not enough to light an LED. Three or four joined together can.
- Each lemon adds roughly the same amount of voltage.
- The glow is dim, because the cell makes only a tiny current.
Why it works
Zinc is more eager to give up electrons than copper. The acid in the lemon lets charged particles move between the two metals. Electrons then flow along the wire from the zinc to the copper, through the LED, and light it. Joining lemons in a chain adds their voltages together, like stacking batteries in a torch. The energy comes from the zinc slowly being used up.
Try this next
- Press the nails closer together or further apart and see what happens.
- Try a different metal in place of copper.
- Count how long the LED stays lit.
Stay safe
Do not eat a lemon after the metals have been in it. Wash your hands. Many coins are not made of copper, so use copper wire.
Link to the grid
Large batteries store grid electricity the same way: chemical energy stored now, released when needed.
Learn how the grid works