Unilateral elements in electrical circuits are components whose behavior or properties depend on the direction of current flow. They exhibit different characteristics for current flowing in different directions. Common examples of unilateral elements include:
1. **Diodes**: Diodes allow current to flow in only one direction (from the anode to the cathode) and block it in the reverse direction. They are essential in rectification circuits.
2. **Transistors (BJTs and FETs)**: Bipolar Junction Transistors (BJTs) and Field-Effect Transistors (FETs) are also unilateral. They control the flow of current through them based on the input signal or voltage applied. For instance, a BJT requires a base current to allow a larger collector current, while an FET uses a gate voltage to control the drain current.
3. **LEDs (Light Emitting Diodes)**: LEDs are a special type of diode that emits light when current flows through them in the forward direction. They behave like diodes in terms of current directionality.
4. **Zener Diodes**: Zener diodes are designed to allow current to flow in both directions but have a specific breakdown voltage in the reverse direction. They are used for voltage regulation.
These elements are characterized by their directional nature, meaning their behavior changes with the direction of the current, unlike bilateral elements (like resistors, capacitors, and inductors) that exhibit the same behavior regardless of the current direction.