CURRENT AND FLOW: AN ELECTRICAL ENGINEER’S GUIDE TO THE CONCEPTS OF FLUID SYSTEMS

Unlike most of my colleagues I didn’t start out with a mechanical background.  While they were studying kinetics and machine design, I was studying digital electronics and industrial power.  When I started my career in the world of pumps, I had to learn a whole new set of concepts.  What was surprising was that while the terminology may be a bit different, the concepts are very similar.  Think of the following as a “Rosetta Stone” for translating the common terms and concepts of fluid systems to your more familiar terms and concepts of electrical systems. 
Electric current is the rate of flow of electric charge.  Think of this as the rate of the flow of electrons passing through a conductor like wire.  Current is most commonly represented by the symbol I and is most commonly measured in amperes (symbol A). 

Flow (or more accurately, flow rate) is measurement of the volume of liquid travelling through a pumping system over a period of time.  Flow rate is commonly represented by the symbol Q and is most commonly measured in gallons per minute (GPM) or cubic meters per hour (m³/hr).  Another common variation of this is mass flow rate wherein the rate of flow is measured by the weight of liquid transferred over a period of time.  This is commonly used by engineers who measure the weight of the vessels to determine the quantity of liquid transferred.  For mass flow rate the common units of measure are pounds per minute (lb/min), kilograms per hour (kg/hr), or variations thereof.