In the hydraulic-electrical analogy, which electrical quantity corresponds to the flow rate of water in a pipe?

• A. Voltage
• B. Current
• C. Resistance
• D. Power

Answer: (B)

In this analogy, the quantity that measures how much stuff moves per unit time is the flow rate. For water, that’s the amount of water passing a point each second; for electricity, it’s the charge passing a point each second, which is electrical current. So current best represents the water flow rate because both describe how much stuff moves per unit time.

Voltage corresponds to pressure difference pushing the water, not the rate of flow. Resistance represents how the pipe’s properties—friction, diameter, roughness—impede flow, shaping the actual current but not equal to it. Power is the rate of energy transfer, which in hydraulics would be pressure difference times flow, not the flow rate itself.