Question

make a battery from four lemon and tested with LED in the circuit

Answer 1

Using the knife, slice a penny-sized slit on the right side of your lemon.

Push the penny far into the lemon, leaving a small area to hook your alligator jumper to. This will be your positive terminal.

Now, create the negative terminal for your battery. Stick one of the galvanized nails into the left side of the lemon, about 2 inches away from the penny. It is important to have the nail and penny separated. If they touch, it will cause a short.

Repeat this process until you have 4 complete batteries.