Ideal & Practical Voltage Sources

There are two types of electric sources: Ideal and practical sources. As the name suggests the ideal source is always imaginary, while the practical source is the one which we use in our practical circuits.

Voltage Source

The voltage source is the type of source which provides us potential difference in particular. Basically the voltage source and current sources are distinguished to understand their properties separately, otherwise, in real practical circuits, in general, voltage source and current source are not differentiable – I am saying this in a very broad sense!

Ideal Voltage Source

The ideal voltage source is imaginary. Its internal resistance is zero. Hence its PD i.e. output voltage is equal to its e.m.f. (E) as shown below.

Practical Voltage Source

The practical voltage source is real. Its internal resistance is greater than zero. Hence its PD is always less than its e.m.f. (E) as shown below.

Current Source

There are two types of current sources: ideal and practical current sources. Again as the name suggests, the ideal current source is imaginary and the practical current source is the one which we use in our practical circuits.

Ideal Current Source

The ideal current source is imaginary. Its internal resistance is infinite. Hence it can give constant current at its output, as shown below.

Practical Current Source

The practical current source is real. Its internal resistance is less than infinity. Hence it cannot give constant current at the output.