Basic Concepts of Electrical Engineering you should Learn Today


Basic Concepts of Electrical Engineering

  1. Linear vs Nonlinear components

  2. Active vs Passive components

  3. Unilateral vs Bilateral components

  4. NTC vs PTC

  5. Conductors vs Insulators

  6. Conventional vs Electrons flow


Linear vs Nonlinear components

A linear circuit is one that has no nonlinear electronic components in it. Examples of linear circuits are amplifiers, differentiators, and integrators, linear electronic filters, or any circuit composed exclusively of ideal resistors, capacitors, inductors, op-amps (in the “non-saturated” region), and other “linear” circuit elements.

Some examples of nonlinear electronic components are: diodes, transistors, and iron core inductors and transformers when the core is saturated. Some examples of circuits that operate in a nonlinear way are mixers, modulators, rectifiers, radio receiver detectors and digital logic circuits.

The behavior of such linear circuit elements as resistors, capacitors, and inductors can be specified by a single number (resistance, capacitance, inductance, respectively). In contrast, a nonlinear element’s behavior is specified by its detailed transfer function, which may be given by a curved line on a graph.

Active vs Passive components

Active components are parts of a circuit that rely on an external power source to control or modify electrical signals. Active components such as transistors and silicon-controlled rectifiers (SCRs) use electricity to control electricity.

Passive components like resistors, transformers, and diodes don’t need an external power source to function. These components use some other property to control the electrical signal. As a result, they only require the current traveling through the connected circuit. Resistors impede the flow of electrons without introducing more electricity into the system.

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Passive Active
Resistor Transistors
Capacitor SCR
Inductor Triac
Transformer BJT, FET, UJT
Diode Gas tube, Thyratron

Unilateral vs Bilateral components

Unilateral Element:

A unilateral contract is a contract agreement in which an offeror promises to pay after the occurrence of a specified act. In general, unilateral contracts are most often used when an offeror has an open request in which they are willing to pay for a specified act.

An example of a unilateral contract is an insurance policy contract, which is usually partially unilateral. In a unilateral contract, the offeror is the only party with a contractual obligation.

Bilateral Element:

Bilateral elements are defined as the elements through which magnitude of current is independent of polarity of supply voltage. This means, the V-I characteristics of such type of element does not get affected by the polarity of voltage. A resistor, inductor, capacitors are example of bilateral circuit elements.



NTC stands for Negative Temperature Coefficient. The NTC thermistor provides variable resistance based on temperature. As temperature increases, the resistance drops from high to low and allows current to pass through. When used for inrush current mitigation, it provides an additional series resistance at power on. As the thermistor self heats with current flow, the resistance drops to a negligible amount during steady-state, allowing normal current flow. 

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NTC thermistors are the most commonly used thermistor. They fit a wide range of applications, including automotive, military, industrial, and emissions controls. Various items around your home contain NTC thermistors, including your oven, air conditioning, and fire detector.


PTC stands for Positive Temperature Coefficient. The PTC thermistor also provides variable resistance based on temperature. As temperature rises, resistance increases from low to high and blocks the overcurrent. Specific scenarios require a PTC thermistor over an NTC thermistor. These include equipment with a near-zero reset time, extreme temperature conditions, and systems that experience frequent shorts.

Conductors vs Insulators


  1. They allow the current of electricity to flow through them.
  2. They have large numbers of free electrons
  3. Metals like silver, copper, iron, gold and wet wood are conductors.
  4. Metals like silver, copper, iron, gold and wet wood are conductors.


  1. They do not allow the current of electricity to flow through them.
  2. They have a small number of free electrons.
  3. Cotton, dry wood, rubber, glass are insulators.
  4. They can be charged by rubbing.

Conventional vs Electrons flow

Conventional Current assumes that current flows out of the positive terminal, through the circuit and into the negative terminal of the source. This was the convention chosen during the discovery of electricity. They were wrong!

Electron Flow is what actually happens and electrons flow out of the negative terminal, through the circuit and into the positive terminal of the source.

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