Difference between ideal and practical/Voltage and Current Source

Sources are devices that convert mechanical, kinetic, chemical or any other form of energy into electrical energy. In other words, sources are active elements of electric circuits that produce electrical energy. Division by function, sources can be classified as voltage and current sources. Theoretically, there are ideal and practical sources. The question is what is the difference between ideal/practical and voltage/current sources?

Ideal sources are those imaginary electrical sources that provide constant voltage or current to the circuit regardless of the load current. These ideal sources don’t have any internal resistance. Where it is impossible to build a source with zero internal resistance. So, all the real sources are called practical sources.

The difference between Ideal and Practical sources is based on the dependency of the source output over the load resistance.

Voltage Source

The electrical sources are those devices that provide voltage to a circuit and their terminal voltage is completely or partially independent of current drawn from it. The purpose of the voltage source is to provide voltage rather than the current and current source is to provide current rather voltage. Theoretically, there are two types of voltage sources available in electrical networks, ideal voltage source, and practical voltage source.  

Ideal voltage source

The ideal voltage source provides a constant voltage at its terminal regardless of current drawn out of it. Ideal voltage sources are only theoretical and can’t be developed in a laboratory. An ideal voltage source doesn’t’ have internal resistance and no voltage drop occurs due to the resistance, so the terminal voltage remains constant.

Practical Voltage Source

Practical voltage sources are real and used in daily life. A practical voltage source has internal resistance that causes a drop in terminal voltage due to the current flow.

Difference between Ideal and practical voltage and current source

Difference between Ideal and practical voltage source

An imaginary voltage source, which can provide a constant voltage to load ranging from zero to infinity. Such voltage source is having zero internal resistance, $R_{s}$ and is called Ideal Voltage Source. Practically it is not possible to build a voltage source with no internal resistance and constant voltage for that long range of the load.

 Practical voltage sources always have some resistance value in series with an ideal voltage source. And because of that series resistance, voltage drops when current passes through it. So, Practical Voltage Source has internal resistance and slightly variable voltage.

Ideal and Practical Voltage Source

Current Source

Current sources are active network elements that provide the same current to any load connected across it. The purpose of a voltage source provides current to a load rather than voltage. Ideal current sources are providing the exact same current to any resistance connected to it. Where practical current sources may vary current resistance.

Ideal Current source

The ideal current source provides exactly the same current to any load resistance and doesn’t change its current with changing a load resistance. Ideal current creation in a lab is not possible and they are only theoretical.

Practical Current Source

Practical current sources are used in day to day life and are easy in manufacturing. They change their current with changing the load resistance due to the internal resistance in it. 

Difference between ideal and practical current source

An imaginary current source, which provides a constant current to any load ranging from zero to infinity. Remember that the current provided is independent of voltage. The ideal current source is supposed to have infinite internal resistance, $R_{s}$. Again it is not practically possible to make one.

Practical Current Source has some internal resistance connected in parallel to Ideal Current Source. And some of the current flow through it and the amount of flow depends upon the load.

Ideal and Practical Current Source

Difference between Dependent and Independent Sources

A voltage source not depending upon other circuit parameters are an independent source. Independent sources provide almost constant voltage/current irrespective of different circuit elements (slightly changed caused by internal resistance).

In case of dependent sources, the output of the source depends upon some circuit parameter. By changing those parameters in circuit output of the source are adjusted. There are four types of dependent sources:

  1. Voltage-controlled Current Source (VCCS), where the current source is dependent on voltage.
  2. Current-controlled Current Source (CCCS), where current source is dependent on current.
  3. Voltage-controlled Voltage Source (VCVS), where the voltage source is dependent on another voltage.
  4. Current-controlled Voltage Source (CCCS), where voltage source is dependent on current source. \(\)
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  1. Jason December 21, 2019

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