ANALOGIES BETWEEN ELECTRICITY AND WATER FLOW

Quantity	Symbol	Units	What it is	Analogue	Units
Charge	q	Coulombs	Electric charge	Water	Gallons
Current	i=dq/dt	Amperes= coulomb/sec	Flowing charge	Water flow	Gallons per second
Voltage	v	volts	Elec. potential	water pressure	psi
Resis- tance	R=v/i v=iR	Ohms	need a field to move a charge	Resistance	Pressure drop:pipe
Conduc- tance	G=i/v G=1/R	Mhos (read backwards)	need a field to move a charge	conductance	Pressure drop:pipe
Ideal wire	R=0	0 Ohms	superconductor	Ideal pipe	no friction
Voltage source	Vs	v=constant	ideal battery or ideal generator	constant pres- sure pump	water tower
Current source	Is	i=constant	ideal solar cell	constant velo- city pump	fountain
Capacitor	i= Cdv/dt	Farads	Stores separ- ated charge	Water tower (stores water)	Gallons, or height
Inductor	v= Ldi/dt	Henrys	Links mag- netic field	None	None
Energy	W=qv	Joules	To move charge across voltage	Potential energy	PE=(mg)h

Another perspective, using height instead of pressure as analogous to voltage:

Quantity	What it is	Water Analogue
KCL (current law)	conservation of charge	water flow in=water flow out
Negative current	actual flow other way	actual flow is the other way
Resistors in series	R=R1+R2	Resistance increases w/length
Resistors in parallel	G=G1+G2	Pipes in parallel increase flow
Voltage (another way)	Electrical potential	Height (gravitational potential)
Kirchhhoff's (KVL) Voltage Law	potential is path-indpt in electric circuits	takes same energy to reach a height regardless of path
Ground potential	Reference voltage	Sea level
Node voltage	Voltage at a point	Height above sea level