A TWO-CENT BATTERY that embodies the fundamental principle of all primary electric cells is easily made. Press a "red" copper cent against one side of a piece of blotting paper saturated with salt water, vinegar, or citrus juice, and press one of the new zinc-coated cents against the other side. Wind several dozen turns of fine, insulated copper wire around a pocket compass so the coil parallels the direction of the needle. If you hold one end of the wire against the copper cent and the other end against the zinc-coated cent, the needle will swing widely. Reverse the wires, and the needle will swing the other way.


BEND ONE END of a copper plate and an amalgamated zinc plate and hang the plates over opposite sides of a tumbler containing dilute sulphuric acid, and you will have a simple battery cell. Provide binding posts and connect the cell to a 11/2-volt flashlight bulb. It will light brightly and then, after a few seconds, will go out because hydrogen bubbles accumulating on the copper plate increase resistance so greatly that they practically stop the current. This action is called "polarization." Wipe off the copper plate, and current will flow again.


DIMES AND PENNIES, piled a shown in the diagram with the pairs separated by squares of blotting paper moistened with salt water, will make a stunt battery. As the copper is acted upon by the salt water more strongly than the silver, current is produced. Alessandro Volta made the first battery in about 1799 by using a similar pile of copper and zinc disks. The word "volt" honors him.

For a stunt, you can make a battery that will show a reading on a sensitive voltmeter or a home-made galvanometer, using only a half dozen pennies, as many dimes, and some bits of blotting paper moistened in salt water, following the directions given on this page.

science Stunts