Electrical analogy for a single-tank liquid system: in the standard hydraulic–electrical analogy, which variable corresponds to electrical voltage?

Introduction / Context:
Analogies help engineers visualize dynamic behavior across domains. The hydraulic–electrical analogy maps variables in fluid systems to electrical circuit counterparts. Understanding these mappings is valuable for intuition about transient responses and controller design.

Given Data / Assumptions:

• System: single tank with inlet and outlet.
• Electrical analogy: voltage ↔ pressure head; current ↔ flow; capacitance ↔ storage capacity.
• Level is proportional to hydrostatic pressure head.

Concept / Approach:
In the analogy, the potential difference driving current in a circuit corresponds to pressure difference driving flow in a hydraulic system. For a tank, the hydrostatic head is directly related to liquid level. Therefore, tank level (head) is analogous to electrical voltage; flow rate corresponds to current; and the tank’s cross-sectional area acts like capacitance storing “charge” in the form of volume per unit head.

Step-by-Step Solution:
Identify electrical voltage as potential energy per unit charge.Map to hydraulic potential: pressure head due to level.Conclude that liquid level (head) corresponds to electrical voltage in the analogy.

Verification / Alternative check:
Mathematically, continuity gives A * dh/dt = q_in − q_out, which mirrors capacitor equation C * dv/dt = i_in − i_out, where A ↔ C and h (level) ↔ v (voltage).

Why Other Options Are Wrong:
Heat content: Belongs to thermal analogies, not directly to hydraulic–electrical mapping.Liquid volume: Closer to electrical charge (C * V), not voltage itself.Flow rate: Corresponds to current, not voltage.Area: Corresponds to capacitance, not voltage.

Common Pitfalls:
Confusing storage (capacitance) with potential (voltage) and mixing thermal–electrical with hydraulic–electrical analogies.

Final Answer:
Liquid level (pressure head)