Resistor Color Coding

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Resistors use various color bands to specify their values. These color bands are used instead of numbers due to their simplicity and cost effective printing on tiny components.

The following table lists the various color codes

Inductance / Inductor

Inductance

Inductance or Inductor indicated by letter ‘L’ is a passive circuit element that stores energy in the form of magnetic field. Inductors are the coils generally wounded over a permeable medium. The windings in electrical machines and transformers

Voltage Source

A voltage source is an active element in electrical circuits which delivers voltage to the circuit. An ideal voltage source should have no internal resistance (or Impedance in AC) and its output voltage is independent of the current passing through the element. The voltage delivered by an ideal voltage source is always

Practical Current source

Practically the current sources don’t have infinite resistance across them but has some finite and high resistance. Due to the finite resistance the practical current source shows some dependency on the voltage across it. So the current delivered by a practical current

Star connection | Y connection

The star connection also called Y - connection or wye connection is a type of circuit configuration in electrical circuits. If three elements in a circuit viz. aa’, bb’ and cc’ are connected in such a way that their ends either a, b and c or a’, b’ and c’ connected all together while

Ideal current source

An ideal current source is an active electrical element which delivers current to the circuit and it has infinite internal resistance across it. The current delivered from the ideal current source is always constant and it is independent of the voltage. The current delivered

Practical voltage source

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A voltage source is an active element which deliver power to the circuit (for example, batteries are the voltage sources). Practically all the voltage sources have some internal resistance in contrast to its ideal case. A practical voltage source is modelled as, an ideal voltage source in series with its internal resistance indicated by a resistor. Due to the presence of the internal resistance the voltage delivered by a practical voltage source is no more constant as in the ideal case,

Ideal voltage source

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An ideal voltage source is an electrical element which delivers voltage to the circuit with no internal resistance. The voltage across the ideal voltage source is constant and it is independent of the current passing through the source. Ideal source is only a theoretical one for understanding and there is no such ideal source with zero internal resistance. Practically the voltage source has some internal resistance and its voltage depends on the

Classification of circuit elements

Classification of Network elements 

All the circuit elements in the electrical circuits can be classified into various types based on the following five classifications:

Active and Passive elements

(go to Active and Passive elements for full article)

In electrical networks the elements which deliver power to the circuit

Time variant and Time invariant Elements

Time invariant elements

An element or a system is said to be time invariant if parameters of the element do not vary with time. For example a resistor is a time invariant element whose value of resistance R or any response by it remains same irrespective of the instant of time when the voltage or current is applied to it. Its value may change with change with change in voltage or current like in a non-linear resistor but still it is called as a time invariant element as long as its response won't with respect to time. The given below figures shows

Unilateral and bilateral elements

Bilateral elements

The impedance offered by the bilateral elements is same for either direction of the current flow. The volt-ampere (V-I) characteristics of bilateral elements are symmetrical on I and III quadrants or on II and IV quadrants. The typical V-I characteristics of bilateral elements

Lumped and Distributed elements

Lumped elements

In electrical circuits if the physical size of the element is negligibly small when compared with wave length of electromagnetic wave propagation then the element is modelled as lumped elements. The lumped element can be represented with its parameters like resistance or inductance with its total value at a place.

Examples: Resistors, inductors, capacitors.

Distributed elements

If the physical size of the element is comparable with wavelength of electromagnetic wave propagation then such an element is modelled as distributed element. In these elements resistance, inductance or capacitance are distributed and cannot be separated and modelled at a single point. These are distributed throughout the circuit.

Example: Long transmission lines-in which the resistance, capacitance and inductance are distributed throughout the line. Elements in high frequency electronic circuits.

Identifying a lumped element or distributed element

Energy transfer in electrical circuits takes place in the form of electromagnetic wave propagation. The velocity of electromagnetic wave is equal to the speed of light which is 3x10⁸ m/s.

The velocity is given by ν=λf

Where ν=velocity=3x10⁸ m/s

             λ=wave length of electromagnetic wave

             f=frequency electromagnetic wave (usually the supply frequency is 60 Hz or 50 Hz but varies for some circuits with high frequency)

The wave length of electromagnetic wave propagation for 60 Hz is given by,

λ=ν/f ⟹ λ=(3x10⁸ )/60= 5000000 m= 5000 km

Consider a transmission line of length of 50 Km.

When this line is operating at 60 Hz, the length of the line is very small in comparison with the wave length of electromagnetic wave as 50 Km << 5000 Km so it can be modelled as lumped element.

Consider the same line operating at 3 KHz,

Then the wave length of electromagnetic wave propagation is,

λ=ν/f ⟹ λ= (3x10⁸ )/(3x10³)= 100000m= 100km.

Though length = 50 km is less than the wave length λ=100 km, the length of the line is comparable is length to that of the wave length of electromagnetic propagation and it has to modelled as distributed element.

Thus the long transmission lines and elements in high frequency circuit are referred to as distributed elements. Kirchoff's laws (KVL and KCL) are applicable only to lumped elements and do not applicable to distributed elements.

Also Read

Classification of circuit elements
Active and passive elements
Linear and Non Linear elements
Unilateral and bilateral elements

Active Elements and Passive Elements

The elements or components in electrical circuits can be classified in to either active or passive elements or components. Active elements are the energy sources which deliver power to the network whereas passive elements are the elements in the network which consume energy.

Active Elements

Power supply elements such as voltage sources and current sources either independent or dependent which deliver power are called active elements. For an active element the ratio of the voltage across it to the current flowing is negative i.e. \[\frac{V}{I}<0\]. For Non-linear elements \[\frac{dV}{dI}<0\].

The graphical representations of active elements can be as follows.

characteristics of active elements

Passive Elements

The elements which consume energy are called passive elements. These elements either convert energy into another form or store energy in electric or magnetic field. The elements such as a resistor, inductor and capacitor are called passive elements. For linear passive elements the ratio of voltage to current is positive i.e \[\frac{V}{I}>0\] and for Non-Linear elements \[\frac{dV}{dI}>0\]

Characteristics of passive element