a floating body always displaces liquid equal to its own weight.
a floating body always displaces liquid equal to its own?
weight
in other words, for an object floating on a liquid surface (like a boat) or floating submerged in a fluid (like a submarine in water or dirigible in air) the weight of the displaced liquid equals the weight of the object. thus, only in the special case of floating does the buoyant force acting on an object equal the objects weight. consider a 1-ton block of solid iron. as iron is nearly eight times as dense as water, it displaces only 1/8 ton of water when submerged, which is not enough to keep it afloat. suppose the same iron block is reshaped into a bowl. it still weighs 1 ton, but when it is put in water, it displaces a greater volume of water than when it was a block. the deeper the iron bowl is immersed, the more water it displaces, and the greater the buoyant force acting on it. when the buoyant force equals 1 ton, it will sink no farther.
archimedes' principle
z-ram relies on the floating body effect, an artifact of the silicon on insulator (soi) process which places transistors in isolated tubs (the transistor body voltages "float" with respect to the wafer substrate beneath the tubs). the floating body effect causes a variable capacitance to appear between the bottom of the tub and the underlying substrate. the floating body effect is usually a parasitic effect that bedevils circuit designs, but also allows a dram-like cell to be built without adding a separate capacitor, the floating body effect then taking the place of the conventional capacitor. because the capacitor is located under the transistor (instead of adjacent to, or above the transistor as in conventional drams), another connotation of the name "z-ram" is that it extends in the negative z-direction.
z-ram