Partial differentiation is used to differentiate mathematical functions having more than one variable in them. In ordinary differentiation, we find derivative with respect to one variable only, as function contains only one variable. So partial differentiation is more general than ordinary differentiation.
Partial differentiation is used for finding maxima and minima in optimization problems.
Also Partial derivatives are used in vector calculus and differential geometry.
Fluid mechanics, heat and mass transfer, and electromagnetic theory are all modeled by partial differential equations and all have plenty of real life applications.
For example,
Fluid mechanics is used to understand how the circulatory system works, how to get rockets and planes to fly, and even to some extent how the weather behaves.
Heat and mass transfer is used to understand how drug delivery devices work, how kidney dialysis works, and how to control heat for temperature-sensitive things. It probably also explains why thermoses work!
Electromagnetism is used for all electricity out there, and everything that involves light at all, from X rays to pulse optometry and laser pointers.
Consider the transverse vibrations in an elastic membrane. The membrane subjected to a transverse load (perpendicular to the plane of the frame) of magnitude q of (x, y), where (x, y) is a system of Cartesian coordinates in the plane of the unloaded membrane. We are interested in calculating the transverse deflection w at (x, y), corresponding to an equilibrium configuration. The transverse vibrations of a tensed membrane are given by solving the PDE equation w xx plus w yy equals to minus q upon T plus rho h upon T into wtt. Here, h is the thickness of the membrane
Link for application of Engg Mathematics : https://studiousguy.com/examples-of-mathematics/