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Course: Exploratorium > Unit 3
Lesson 2: Penny BatteryWhat's going on: Chemical energy into electrical energy
What's the science behind this activity? A battery is chemical energy converted into electrical energy. Created by Exploratorium.
Want to join the conversation?
- Everybody knows that batteries go dead after a while. Do these penny batteries go dead? How? What does it take to revive them? New salt water pads? Re-sand the batteries? New pennies?(21 votes)
- Yes, these penny batteries do go dead after a while, but they can go as long as any battery if you make them big enough. You can revive them but you don't need to get new pennies or re-sand them. You only need to get new salt water pads because the salt water pads are the ones that pass the electricity through the penny battery.
PS. You can also use cardboard instead of salt water pads.(15 votes)
- If you added more pennies, would it be more powerful?(2 votes)
- How can you design a more powerful penny battery?(2 votes)
- The video says that "electrons are created". Isn't that impossible due to the Law of the Conservation of Mass and the Law of the Conversation of Energy?(2 votes)
- It means that electrons are being transferred from one metal to the other.(1 vote)
- So if you added more pennies with zinc sides and more salt water/vinger salt pads with a copper coin at say the very top, it increases the voltage?(2 votes)
- so the Voltage of the battery was determined by the chemistry and types of metal. But what kind of chemistry is the best for a battery is it salt and vinegar or there may be some better chemicals?(1 vote)
- The reaction forming electrons is what creates the batteries electric charge. This is a basic self-made battery, helping us understand why the electrons are created and how they flow through the battery, thus powering the LED.(1 vote)
- What reactions create the electrons in the activity?(1 vote)
- Znº --> 2e- + Zn(II) is my guess.
I also suspect that Cu+ and 1e- —> Cuº
Or Cu2+ and 2e- —> Cuº(1 vote)
- Will more pennies generate more volts(1 vote)
- Could a regular battery be used in place of this self-made battery as the energy source for the LED?(1 vote)
- Yes, absolutely. But 1 AA or AAA battery probably won't have enough voltage (1.5 V) to turn on an LED, and a 9V battery might burn out the LED and break it. So a watch battery with 3V will work great. My son did just that today at school. Or put 2 AA or AAA batteries end to end (+ to -) and use 2 wires to connect the + end to (I think the longer wire sticking out of the LED) and the - of the other battery to other (the shorter) wire of the LED. (Or maybe + to shorter wire of the LED and the - to the longer, I not positive.)(1 vote)
- Can't u also use quarters(1 vote)
- No, because quarters are made of a mixture of copper and nickel and the battery needs 1 side of copper and 1 side of zinc to work.(1 vote)
Video transcript
- [Voiceover] So, how
does this battery work? A battery is just a device that converts chemical energy into electrical energy. In each of these four cells, there are two reactions taking place, one that creates electrons
and one that uses them, and when those electrons flow, that's what we call electricity. On the surface where the zinc is in contact with the saltwater, there's a reaction that creates electrons, and on the surface where the copper is in contact with the saltwater, there's a reaction that uses electrons. When you connect the top and
the bottom of this battery with something that conducts electricity, then those electrons will
flow through that object, like this LED. The voltage or electric
potential that each cell produces is determined by the
chemistry of this battery, and a zinc/copper cell produces
a little over half a volt. So four of these cells makes a battery that produces a little over two volts. A red LED requires around 1.7
volts of power to light up. So your two-volt battery is
plenty to light your red LED.