The Passive Sign Convention is a widely used convention in electrical engineering and circuit analysis. It provides a standard way of representing the direction of current flow, voltage polarities, and power dissipation in circuit elements. The convention is based on assigning polarities and currents in a way that follows the actual physical behavior of the elements.
In the Passive Sign Convention:
Current direction: For passive circuit elements (like resistors, capacitors, and inductors), the current is assumed to flow from the higher voltage side to the lower voltage side of the element. This means that the positive sign of the current is taken in the direction of electron flow (opposite to the conventional current flow, which assumes current flows from positive to negative).
Voltage polarity: For passive circuit elements, the voltage across an element is considered positive when the higher voltage is at the terminal where the current enters the element, and negative when the higher voltage is at the terminal where the current exits the element.
Power dissipation: Positive power indicates power dissipation (i.e., energy being converted to heat or other forms of energy) in a circuit element. This happens when the current enters the positive voltage terminal. Conversely, negative power indicates power absorption (i.e., the element is consuming energy from the circuit) when the current enters the negative voltage terminal.
By using the Passive Sign Convention consistently in circuit analysis, it becomes easier to understand the behavior of individual circuit elements and calculate circuit parameters such as voltages, currents, and power dissipation accurately. It also ensures that the signs of various equations remain consistent throughout the analysis.