First, flip all the lemons, one at a time. Squeeze by hand while turning until it feels a little "soft". This is done to produce more juice in lemons. This step is very important; Because this can help you get the best effect of lemon battery. Screw the galvanized screw into the lemon at about 1/3. Carefully cut a1/3cm incision on the other side of the lemon with a knife. Note: It is best to use a knife by an adult. Anyway, please use this knife "carefully" and "slowly". Insert the copper coin into the incision until half of the copper coin is in the lemon. Note: Make sure you use shiny new coins. If the coin is old and dull, polish it with Burgess. Believe it or not, you can get current from lemon now! Like other batteries, the coin is its positive pole (+) and the screw is its negative pole (-). Unfortunately, this kind of battery is very fragile. But if you have several such batteries, you can connect them together to form a lemon battery pack. Insert coins and screws into the other two lemons like this. Then, connect the screws on the first lemon with the coins on the second lemon with wires and clips, and so on, thus connecting the three lemon batteries together. At the same time, connect the wire to the first coin and the last screw with clips. Finally, mark the clip connecting the first coin with "+"and the clip connecting the last screw with "-". Like a real battery, a lemon battery has a positive electrode (+) and a negative electrode (-). When connected in series like this, the voltage or potential generated by these lemon batteries is the same as that generated by several small flashlight batteries in series, which is about 2.5 volts to 3 volts. But the lemon battery pack can't generate enough current to make the flashlight bulb glow. How can we see that the battery pack is really realized? One way is to connect electrical equipment that only needs 2.5 volts to 3 volts and does not need too much current to the battery pack. You can use a device called light emitting diode, which can also be called led for short. Very low voltage, very low current can make LED shine. The description on the LED packaging box we use is: 5 mm red LED, 1.8 volts, 20 mA. This means that the LED has a diameter of 5mm and only needs 1.8V and 20mA to emit light. In fact, a current less than 20 mA can make the LED emit light slightly. Our lemon battery has enough voltage but not enough current. So we need to find some ways to observe the weak light. We put it in a film box to keep it out of the outside light. Using nails, carefully drill two small holes about half the height outside the film shell. You can ask an adult to help you achieve this step. Next, mark a hole with+and use-. Bend the LED pin outward into a smooth curve. Then look at the LED carefully. It's basically round. However, if you tilt it to a specific angle, you will see a plane near the needle. The needle closest to this plane is the negative electrode. In the photo, the pin on the left is the negative electrode of the LED. Can you see the facet near the leftmost pin? Align the negative lead of the LED with the small hole marked with "-"on the film casing. Insert the LED into the film box. Pass the negative lead of LED through the hole marked with "-",and then pass the other (positive) lead through the hole marked with "+". Pull the pins out of the holes and check them to make sure they are consistent with the labels. Also put a label on the top of the film shell. Make sure the LED is facing us. Let's get everything ready and wait for the last moment. Align the side marked with "+"on the film box with LED with the clip marked with "+"on the lemon battery pack. Put the clip marked "-"on the lemon battery pack on the side marked "-"on the film box. Now everything is ready! Connect the positive electrode of LED to the positive electrode of lemon battery. Connect the negative electrode of LED to the negative electrode of lemon battery. The LED is shining! But the light emitted by LED is very dim, because the current emitted by battery pack is too small. The black film shell can help you observe the dim light. The end of the LED acts as a magnifying glass. When you look directly at the end of the LED, you can easily see the luminous phenomenon. This proves that you really succeeded in making a usable lemon battery! Congratulations!