# Source of electrical energy

**The source of electrical energy are classified into two group :**

- Voltage source
- Current source

**These sources are further classified into two types as:**

- Ideal sources
- 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 l_{L} 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 V_{1} =V_{2}

## 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 V_{L} or loads resistance R_{L}.

### 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.

**I _{1} = I_{2}**

**practical current sources**

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