How to DIY a battery using three copper coins

This is a very simple little Handmade diy. It is mainly shared with children, with the purpose of cultivating childrens interest in natural science and improving childrens hands-on ability.
Experimental materials: three copper coins (five-cent coins in China), three washers, and three cardboards cut according to the size of the coins.

Soak the cardboard in vinegar , fully soak the cardboard, only three cardboards are needed between the three coins.

Place the gaskets on the aluminum foil in sequence , wet cardboard, copper coins, and then put the other two in the same order as before. Finally, they are stacked together to form a battery, with the positive electrode at the top and the negative electrode at the bottom. Finally, wrap the "battery" with insulating tapeOkay, and connect the wires!

Connect the wire to the calculator, Try turning it on, and it can actually drive the calculator!