Voltage Source

A voltage source is an active element in electrical circuits which delivers voltage to the circuit. An ideal voltage source should have no internal resistance (or Impedance in AC) and its output voltage is independent of the current passing through the element. The voltage delivered by an ideal voltage source is always

constant for any amount of current supplied by the source. Practically there is no such a voltage source and has some internal resistances. The internal resistance (or impedance) for a practical voltage source is represented by a resistance (or impedance in case of AC circuit) in series with the source.

Symbol of Voltage Source

The given below figures shows the voltage source and the representation of the practical voltage source with internal resistance indicated by resistor R_s.

ideal Voltage Source

practical voltage source

The output voltage delivered by a practical voltage source is given by V_t=V_s-R_si

In alternating current circuits the voltage and the currents are the functions of time and they can be represented with V_s(t),V_t(t) and i(t) and the internal resistance R_s can be replaced by internal Impedance Z_s.

Characteristics of Voltage source

The volt-ampere (V-I) characteristics of the voltage sources can be seen from the following figure. The characteristic of the ideal source is constant irrespective of the current whereas the voltage for a practical voltage will have some drop due the internal resistance.

V-I characteristics of voltage source

Related Topics:

Ideal Voltage Source

Practical Voltage Source