Electrode
Electrode is a metal piece that moves electricity into or out of something, like the zinc strip in a potato battery.
A metal spoon rests in a glass of juice. The spoon is the electrode — it is the solid bridge between the liquid and the wire you clip to it. One spoon lets electricity enter the juice; a second spoon on the other side lets it leave. The juice only conducts because both spoons are there to carry the current in and out.
Explaining electrode by grade level
A potato battery has two metal strips stuck into it. One strip sends power out. The other strip takes power in. Each metal strip is called an electrode.
Projects that explore electrode
Electrodes do not have to look alike. In a Biefeld-Brown lifter, copper wire runs along the top of a frame while aluminum foil wraps around the lower section — two very different electrodes in the same circuit. A power supply moves electricity into one and out of the other. The strong voltage that builds between them produces enough force to lift the entire frame off the ground.
Electrodes can be used to test whether a material conducts electricity. You insert copper electrodes into a beaker of wet soil and connect them to a battery and a milliammeter. Electricity moves into the soil through one electrode and out through the other, and the milliammeter shows how much current passes through.
The same electrodes can behave very differently depending on what surrounds them. Here, copper electrodes sit in two beakers — one filled with distilled water, one with sea water. Electricity barely moves through the distilled water. In sea water, though, the current jumps high enough to light a bulb. What sits between the electrodes matters as much as the electrodes themselves.
A penny and a galvanized nail serve as the electrodes here. Each one moves electricity into or out of the lemon, turning a piece of fruit into a working battery.