Passive, Active, Linear, and Nonlinear Circuits
Simply stated, electronic components that produce energy are active and create nonlinear circuits. Components that store or maintain energy are passive and create linear circuits.
In a circuit, an active component is a device that can control electric current with an external source of energy, either electric voltage or electric current. The part of the circuit that provides energy to the active component is called the direct current (DC) part of the circuit. An active circuit is a circuit with at least one active component. Active components provide power gain or amplification that produces voltage signaling that is discontinuous or nonlinear. Active components include diodes, transistors, and silicon-controlled rectifiers (SCRs). Examples of nonlinear circuits are mixers, modulators, and digital logic circuits.
Components that are incapable of controlling current by means of another electrical signal are called passive devices. An electronic circuit consisting entirely of passive components is called a passive circuit. Resistors, capacitors, inductors, and transformers are all considered passive devices. Passive components cannot introduce energy into a circuit. They also cannot rely on a source of power, except for what is available to them from the circuit they are connected to. Passive components cannot amplify the power of a signal, although they may increase the voltage or current. The signal processing in a passive circuit is continuous or analog.
Analog circuits are circuits where the signal is contiguous; it can assume any value between no power to full power. Digital circuits present a discrete signaling, assuming either no power or full power values (“all or nothing”), with no intermediate steps. A linear circuit is one in which the values of the electronic components (resistors, capacitors, inductors, etc.) do not change with the level of voltage or current in the circuit. Linear circuits are important because they can amplify and process electronic signals without distortion. An example of an electronic device that uses linear circuits is a sound system. A linear circuit is one that has no nonlinear electronic components in it. Examples of linear circuits include amplifiers, differentiators, integrators, and linear electronic filters.
The three types of active components shown are a diode (a cylinder with a lead coming out each end), a transistor (a component with three leads coming out of it), and an SCR (a component with three leads coming out of it). The three types of passive components are a resistor (a tube with colored stripes on it and a lead coming out of each end), an inductor (a circle with coils wound around it and two fine leads coming off one of the coils), and a capacitor (a cylinder with two leads coming out of the bottom of it).
Examples:
Direct Current vs. Alternating Current
Direct current (DC) is a type of current in which the flow of electrons goes one way only. Direct current is produced by sources such as batteries, power supplies, thermocouples, solar cells, or dynamos. Direct current is used to charge batteries and as power supply for electronic systems. Direct current can be obtained from alternating current by using a rectifier to convert AC into DC. Rectifiers force current to flow in one direction only and are commonly found in an AC to DC power supply.
Alternating current (AC) is an electric current in which the flow of electric current periodically reverses direction. AC is the form in which electric power is delivered to businesses and residences. The usual waveform of alternating current in most electric power circuits is a sine wave. In certain applications, different waveforms are used, such as triangular or square waves. Alternate current is produced in the electrical power plant by taking advantage of various forms of mechanical energy (water flowing from a dam or the spin of a wind turbine) to move large scale alternators. The alternators then transform the mechanical energy into electricity. Direct current produced by a solar plant may be converted into alternating current with an inverter or a motor-generator set.
The direct current graphic shows three batteries. The alternating current graphic shows an electrical wall outlet.
You can use this resources:
https://www.khanacademy.org/science/electrical-engineering
and other
For Lab – measurement of current with diode in circuit, inductance, capacitor . Other.
Example:
