A floating object can be used to actuate a switch mechanism when the liquid level in an tank
rises past a certain point. If the liquid is electrically conductive, the liquid itself can be used as
a conductor to bridge between two metal probes inserted into the tank at the required depth.
The conductivity technique is usually implemented with a special design of relay triggered by
a small amount of current through the conductive liquid. In most cases it is impractical and
dangerous to switch the full load current of the circuit through a liquid.