# Source of electrical energy

The source of electrical energy are classified into two group :

1. Voltage source
2. Current source

These sources are further classified into two types as:

1. Ideal sources
2. Practical source

## Voltage source

### Ideal Voltage Source

An ideal voltages sources are defined as the voltage source which provides a constant terminal voltage across the load for any variation of load current lL or load resistances R.

### Practical Voltage Source

It is not possible to get the ideal voltage source producing a strictly constant voltage across its terminals while supplying the current.

Voltage source in series

The two practical voltage sources in series can be combined together to get a single equivalent voltage source.

Voltage sources in parallel

For parallel combinations of two ideal sources, their voltages must be same with the same polarities as V1 =V2

## Current sources

### Ideal current sources

An ideal current source is defined as the current source which provides a constant current through the load for any variation of load voltage VL or loads resistance RL.

### Practical current Practical

Practically it is impossible to visualize the ideal current source supplying a strictly constant current through the load across terminals a and B.

Current sources series

For series combinations of two ideal current sources, their current must be the same in magnitude and directions.

I1 = I2
practical current sources

The two practical current sources in parallel can be combined together to get a single equivalent current source.