Water-and-Pipe Analogy for Ohm’s Law

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An analogy for Ohm’s Law
An analogy for Ohm’s Law

Ohm’s Law also makes intuitive sense if you apply it to the water-and-pipe analogy. If we have a water pump that exerts pressure (voltage) to push water around a ”circuit” (current) through a restriction (resistance), we can model how the three variables interrelate.

If the resistance to water flow stays the same and the pump pressure increases, the flow rate must also increase.

Pressure = IncreaseVoltage = Increase
Flow rate = IncreaseCurrent = Increase
Resistance = SameResistance = Same

Ohm's law analogy (1)

If the pressure stays the same and the resistance increases (making it more difficult for the water to flow), then the flow rate must decrease:

Pressure = SameVoltage = Same
Flow rate = DecreaseCurrent = Decrease
Resistance = IncreaseResistance = Increase

Ohm's law analogy (2)

If the flow rate were to stay the same while the resistance to flow decreased, the required pressure from the pump would necessarily decrease:

Pressure = DecreaseVoltage = Decrease
Flow rate = SameCurrent = Same
Resistance = DecreaseResistance = Decrease

Ohm's law analogy (3)

Review of Water-and-Pipe Analogy for Ohm’s Law

  1. With resistance steady, current follows voltage (an increase in voltage means an increase in current, and vice versa).
  2. With voltage steady, changes in current and resistance are opposite (an increase in current means a decrease in resistance, and vice versa).
  3. With current steady, voltage follows resistance (an increase in resistance means an increase in voltage).

Resource: Lessons in electric circuits , Volume I – DC

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Edvard Csanyi

Edvard - Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV/MV switchgears and LV high power busbar trunking (<6300A) in power substations, commercial buildings and industry fascilities. Professional in AutoCAD programming. Present on