Types of Sources

TYPES OF SOURCES

According to their terminal voltage-current characteristics, energy source are categorized into ideal voltage sources and ideal current sources.

Ideal voltage source:

An ideal voltage source is a two terminal element in which the voltage V_s is completely independent of the current i_s through its terminals. An ideal voltage source is shown in fig 1.7.

It is observed that V-I characteristics for an ideal voltage source at any time the value of the terminal voltage V_s is constant with respect to the value of current i_s

Practical voltage source:

In practical voltage sources, the internal resistance is represented in series with the source. In this, the voltage across the terminals falls as the current through it increases. The terminal voltage V_t = V_s - i_s R. Practical voltage source is shown in fig 1.8.

Ideal current source:

An ideal current source is a two terminal element in which the current i_s completely independent of the voltage V_s across its terminals. An ideal current source is shown in fig 1.9.

At any time value of the current i_s is constant with respect to the voltage across it.

Practical current source:

In many practical current sources the resistance is in parallel with a source. The magnitude of the current falls as the voltage across its terminals increases. The terminal current i_t = i_s – ﴾V_S /R﴿. Practical current source is shown fig 1.10.