Circuit Fundamentals

# Electric circuit elements / active elements

A circuit is an interconnection of circuit elements. And analysing circuits we determine voltages and currents through the circuit elements. Let’s assume that all elements in our electric circuits are ideal – ideal models. There are two types of elements in electric circuits: ideal passive and ideal active elements. The difference between them is that passive elements can not generate electrical power in a circuit, active elements can.

Active electric elements are current and voltage sources, while passive elements  are resistors, conductors, inductors and some others.

Let’s take a look at the types of power sources.

### Power sources can be two types: independent and dependent ones

Ideal independent source is the source delivering voltage or current into a circuirt  independetly of other elements.

It means that this source can deliver any current or voltage necessary, independently of the level of voltage/current of the circuit elements.

Ideal dependent source is a source which quantity is controlled by another circuit element. There are four types of depandent source elements:

• A voltage-controlled voltage source (VCVS);
• A current-controlled voltage source (CCVS);
• A voltage-controlled current source (VCCS);
• A current-controlled current source (CCCS).

Here are the symbols used for the sources listed above: