Cola Light

Project Number: 64

Description: Assemble the liquid energy source using the instructions on page 4. Build the circuit and connect the red & black jumper wires; the red wire goes to the copper electrode. Set the meter (M6) to the 5V setting. Fill the compartments with cola soda (other soda flavors and lemon, tomato, or grapefruit juice also work). Set the slide switch (S5) to position B. The meter shows the voltage produced. Now set the slide switch to position C to connect the red LED (D1). The LED should be on, though it may be dim. The voltage shown on the meter may be lower now, because the cola may not be able to make as much electricity as the LED wants. If you watch the circuit, the LED brightness and the voltage may slowly drop as the cola reacts with the electrodes to produce electricity. Remove the meter from the circuit. The LED may be brighter, because all the electricity produced is going to the LED now. You can move the copper electrode with the snap on it over to the next compartment, as shown in the Liquid Battery project. The LED will be dimmer or it will not light at all, because the voltage is lower. If the copper and the zinc electrodes get corroded through use, use sandpaper, steel wool, or a scraper to remove the corrosion and to improve performance. Don't drink any soda or juice used in this project. Wash the electrodes and the liquid holder.

Snappy: When used to measure voltage (5V setting), your M6 meter has a high resistance of about 10K ohm, which is placed in parallel with the voltage you are measuring. A very small amount of current will be diverted into the meter, but this will usually not have any affect in the circuit. However, sometimes, if your voltage source can only produce a small amount of current, it does change the circuit operation. That is why the LED can get brighter when you remove the meter from this circuit. When used to measure current, your M6 meter has a resistance of about 500 ohm in the 0.5mA setting and about 10 ohm in the 50mA setting, which is placed in the circuit so the current flows through it. The meter resistance will reduce the current it is trying to measure, but the effect will be small if the meter is set to the appropriate current scale. Your M6 meter is a simple meter. Normal electronic test instruments can make better measurements, because they have less effects on the circuits they are measuring, but even they have limitations and they can be very expensive.