Electrical – fluid (hydraulic) analogy

The following table shows some analogy between electrical and fluid systems. It is useful for people who want to understand one of these systems by comparing with another system. Also, it’s pretty useful for hydraulic circuit designers as they may get ideas from existing electronic circuits and apply it to hydraulics.

Electrical	Hydraulic
Electric current intensity (Ampere = Coulomb\sec)	Mass flow rate (kg\sec)
Electric potential difference (voltage difference)	Pressure gradient (difference)
Electric charge quantity	Fluid mass
Flexible wire	Flexible hose
PCB (Printed Circuit Board)	Rigid pipes
Diode	Check valve (one-way valve)
Electric capacitor	Elevated tank or accumulator
Triger diode DIAC	Pressure regulator valve
Battery	Pump
On /off switch	Valve fully-opened/fulley-closed
Electric resistance	Pipe friction, entrance and exit losses, and fittings losses.
Potentiometer (variable resistance)	Proportional valve
Fuse
Step down transformer: Reduces voltage and increases current intensity	Nozzle: Increases velocity and reduces pressure
Step up transformer: Increases voltage and decreases current intensity	Diffuser: Decreases velocity and increases pressure
Inductance: Shows some impedance when electric current changes and has zero impedance when current is fixed	Rotary motor: Shows some impedance when mass flow rate changes (due to rotor inertia).
AC current	Pulsating flow
Dielectric insulator	Seal
Reference → Earth (ground)	Reference → Free surface (atmospheric pressure)
Comparator	Differential valve
Logic gate OR	OR (shuttle) valve
Relay	Hydraulic-actuated valve
Optocoupler	Hydraulic coupling
Electric surge	Water hammer
Eddy current	Turbulent flow
KCL	Continuity equation
KVL	Bernoulli equation
Ameter	Flow meter
Voltameter	Pressure gauge
Medium: electric conductor	Medium: fluid
Electric resistivity	Fluid viscosity
Circuit breaker	Isolation valve
Amplifier	Hydraulic intensifier
Bundle cables	Laminar flow element