How to build a bridge from electricity and waterS

Mixing electricity and water is rarely a good time for the mixer, but it does make for some entertaining videos. In one particular case - that of a water bridge - the experience is even educational. Under just the right circumstances, electricity and water form a floating bridge between two containers.

First demonstrated by William Armstrong in the mid-1800s, the water bridge, or water thread, is still being studied today. Grab two beakers and set them down on an insulated surface. Fill each to the brim with deionized water. Either string a tiny thread between the two beakers or let the water in them touch just at the spout. Then apply a charge difference between them and slowly move them apart. Generally the thread gets swept into one beaker or the other right away, and left behind is a floating bridge of water.

The water is being transported along the bridge from the positively charged beaker to the negatively charged beaker, although they flow can reverse occasionally. The bridge can grow to be about two centimeters wide. It holds as long as the charge remains and the water doesn't get too hot.

Scientists think that an electrostatic charge builds up on the surface of the water. An electrostatic charge is charge that sits on the surface of an insulator. Water molecules tend to hold more of their electrons on one side than on the other, causing one side of each molecule to have a slightly negative charge while the other side has a slightly positive charge. The electrostatic charge causes the initial bridge to form. Scientists believe that the charge, and the structure, move inside the water itself - studies have shown that the bridge gets denser towards its center, away from the two beakers. These structure supports and moves the water from one beaker to another, holding out against both gravity and water's tendency to break up into drops when not contained. Once the water temperature climbs too high, the chaotic jiggling of the water molecules breaks up the bridge. In the meantime, it's a pretty good show.

Via Physics.org and AIP.

Top Image: José Manuel Suárez