Difference between Ideal and practical, Voltage and Current Source

Electrical sources are devices that convert other forms of energy to electrical energy. Other forms may be mechanical, kinetic, chemical, or potential energy. In other words, sources are active elements of electric circuits. It produces 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 and practical and voltage/current sources?

Ideal sources are those imaginary electrical sources. That provides 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.

Types of Voltage Sources

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

Ideal voltage source

The ideal voltage source provides a constant voltage at its terminal regardless of the 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 Source

An imaginary voltage source can provide a constant voltage to load ranging from zero to infinity. Such a voltage source has zero internal resistance, R_s, and is called an 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, the Practical Voltage Source has internal resistance and slightly variable voltage.

Types of Current Sources

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

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What is an Ideal Current Source?

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

What is a Practical Current Source?

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

Difference between an 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.

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

Difference between Independent and Dependent Source

Independent Source

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

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Depended Source

In the case of dependent sources, the output of the source depends upon some circuit parameter. By changing those parameters in the circuit output of the source is 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 the current source depends on current.
3. Voltage-controlled Voltage Source (VCVS), where the voltage source depends on another voltage.
4. Current-controlled Voltage Source (CCCS), where the voltage source depends on the current source.