We are making paper circuits at school. The students will be making a circuit using double-sided copper tape, an LED (in various colors, R/Y 2.0-2.2 volts, B/G/W 3.0-3.2 volts) and a power source.
Which battery should we use? Maybe a CR2032 or CR2025?
Small lithium coin cells have a relatively high internal resistance and thus may serve as the current limitation to protect LEDs from over-current (more on this here). The only difference between 2032 and 2025 cells is size and capacity. (The first two digits, 20, refers to the diameter. The last two digits, 32 and 25, refer to the cylinder length or thickness in this case. The -25 is 2.5 mm thick, while the -32 is 3.2 mm thick.)
If your project has any dimensional requirements (e.g. battery must fit into some enclosure) then your choice will largely be dictated by that. Otherwise, the 2032 will have greater capacity and run the LED for a longer period of time. The datasheets I linked above list the following capacities:
If the run time isn't important, go with whatever cell you can get more affordably (I'm assuming you are a teacher and your budget is limited.)
