<P> The explanation of this instability begins with the existence of tiny perturbations in the stream . These are always present, no matter how smooth the stream is . If the perturbations are resolved into sinusoidal components, we find that some components grow with time while others decay with time . Among those that grow with time, some grow at faster rates than others . Whether a component decays or grows, and how fast it grows is entirely a function of its wave number (a measure of how many peaks and troughs per centimeter) and the radii of the original cylindrical stream . </P> <P> J.W. Gibbs developed the thermodynamic theory of capillarity based on the idea of surfaces of discontinuity . He introduced and studied thermodynamics of two - dimensional objects--surfaces . These surfaces have area, mass, entropy, energy and free energy . As stated above, the mechanical work needed to increase a surface area A is dW = γ dA . Hence at constant temperature and pressure, surface tension equals Gibbs free energy per surface area: </P> <Dl> <Dd> γ = (∂ G ∂ A) T, P, n (\ displaystyle \ gamma = \ left ((\ frac (\ partial G) (\ partial A)) \ right) _ (T, P, n)) </Dd> </Dl> <Dd> γ = (∂ G ∂ A) T, P, n (\ displaystyle \ gamma = \ left ((\ frac (\ partial G) (\ partial A)) \ right) _ (T, P, n)) </Dd>

Define surface tension.state its si unit and dimensions