Difference between Ideal and Real voltage source
An ideal voltage source will maintain the desired voltage across its terminal irrespective of the magnitude and direction of the current being drawn from it.
An actual voltage source’s output voltage drops when more current is drawn (as shown in the following figure). It is modeled as an ideal voltage source with series resistance. The voltage drop happens because of drop (also called IR drop) across the RS. So, the effective voltage across the load resistance drops, which is undesirable. Therefore a voltage source having less source resistance is usually preferred.
Difference between Ideal and Real current source
An ideal current source will push/pull the desired current across its two terminals irrespective of the magnitude and direction of the voltage.
An actual current source’s output current changes depending on the output voltage. Usually, it is modeled as an ideal current source with a large parallel resistance. As the voltage increase, the parallel resistance (RP) steals some current due to which there is lesser current available for RL.
