| 60 | | * cut a slit at each end of the lemon with the knife |
| 61 | | * slip the penny (or copper wire) half-way into one slit |
| 62 | | * slip the washer (or nail) half-way into the other |
| 63 | | * use your multimeter to measure the voltage between the penny and the washer (should be nearly 1V) |
| 64 | | * What happened: lemon juice is acidic and reacts with the copper penny and the zinc-plated washer. The reaction with the zinc results in extra electrons at the washer giving it a negative charge; the reaction with the copper yields hydrogen ions leaving it positively charged. If a conductive path (circuit) exists from the washer to the penny, as electrons flow through the circuit, they allow the zinc-lemon reaction and the copper-lemon reaction to proceed and you've made electricity flow! |
| | 60 | * The two metals (copper and zinc) will form the electrodes (terminals) of the battery. If you are using a penny and a washer, use your knife to cut a small slit at each end of the lemon, a little smaller than the round object's diameter to make it easier to insert the electrodes. |
| | 61 | * slip the copper into one end of the lemon, leaving some of it sticking out to serve as a battery terminal |
| | 62 | * slip the zinc into the other end of the lemon, leaving some of it sticking out to serve as the other battery teminal |
| | 63 | * use your multimeter to measure the voltage between the zinc and copper terminals |
| | 64 | * Bonus points for AP chemistry students: calculate the electron volts associated with each of the two reactions in the battery |
| | 65 | * What happened: the citric acid in the lemon juice reacts with the copper and the zinc: the Zinc reaction releases electrons (oxidation) and the Copper reaction consumes electrons (reduction). If you've taken chemistry, you've learned about ''redox'' reactions; to see this in more detail watch [https://www.youtube.com/watch?v=Rt7-VrmZuds this 9 minute video]. If a conductive path (circuit) exists from the Zinc anode to the Copper cathode, as electrons flow through the circuit, they allow the redox reaction to proceed, and you can use the flowing electrons (electricity) to do work! |
| 85 | | * What happened: the two jumper wires and the filament in the bulb provide a path (circuit) for the electrons to flow from the negative battery terminal to the positive battery terminal. As the electrons flow through the circuit, the resistance they encounter as they push their way through the bulb's filament cause it to get hot, glow, and emit light. |
| | 86 | * What happened: the two jumper wires and the filament in the bulb provide a path (circuit) for the electrons to flow from the negative battery terminal to the positive battery terminal. As the electrons flow through the circuit, the resistance they encounter as they push their way through the bulb's filament cause it to get hot, glow, and emit light. The LED works a little differently, but the concept is the same: some of the electrical energy moving through the LED is converted to light energy. |
| | 87 | * Bonus activity: make your own light bulb. See the [https://www.youtube.com/watch?v=wucmSj7Z-dA Crazy Russian Hacker]. Note: if you wanted the filament to last longer, you would fill the glass with an inert gas like Argon and seal it. |
