ELECTRIC SOURCES

Definition: A source of electrical power (electrical energy), a device that supplies electrical current. It can be electrochemical (battery or fuel cell) or an electromechanical device (dynamo) or a specialized electronic instrument. Also called "power source (supply)".

There are two types of electric sources namely voltage source and current source.

Voltage source:

A voltage source is a two terminal device which can maintain a fixed voltage.

•         Time Invariant Voltage Source: the output terminal voltage of the source changes with time.

•         Time Variant Voltage Source: the output terminal voltage of the source does not change with time.

•         Ideal Voltage Source: Delivers constant voltage irrespective of the current drawn through its terminals. So it produces infinite energy. It has no internal resistance. So no loss.

•         Practical Voltage Source: Has internal resistance. Hence has losses.

Current source:

The current source is a simple circuit, which will provide a current which remains constant regardless of the load placed at its output.

•         Time Invariant Current Source: the source in which current is not varying with time.

•         Time Variant Current Source: the source in which current is varying with time.

•         Ideal Current Source: Delivers constant current irrespective of the voltage drawn across its terminals. So it produces infinite energy. There is no internal resistance. So no loss.

•         Practical Current Source: Has internal resistance. So has losses.

Dependent and Independent Sources:

Dependent Sources: Produces current or voltage dependent on other circuit elements.

•         Voltage Dependent Voltage Source: Produces output voltage as a function of another voltage value.

•         Voltage Dependent Current Source: Produces output current as a function of a voltage value.

•         Current Dependent Current Source: Produces output current as a function of another current value.

•         Current Dependent Voltage Source: Produces output current as a function of a voltage value.

Independent Sources:

Independent sources produce current or voltage independent of other circuit elements.

·         Independent Voltage Source: produces current necessary to maintain constant voltage output independent of other circuit elements.

·         Independent Current Source: produces voltage necessary to maintain constant current output independent of other circuit elements.