DC Network Theorems - Independent and Dependent Sources
DC Network Theorems – Independent and Dependent Sources
Those voltage or current sources, which do not depend on any other quantity in the circuit, are called independent sources. An independent d.c. voltage source is shown in Figure given below.
whereas a time-varying voltage source is shown in Figure given below.
The positive sign shows that terminal A is positive with respect to terminal B. In other words, potential of terminal A is v volts higher than that of terminal B.
Similarly, Fig given below, shows an ideal constant current source
Figure given below depicts a time-varying current source.
The arrow shows the direction of flow of the current at any moment under consideration.
A dependent voltage or current source is one which depends on some other quantity in the circuit which may be either a voltage or a current. Such a source is represented by a diamond-shaped symbol as shown in Figures given below. To avoid confusions with an independent source. There are four possible dependent sources :
1. Voltage-dependent voltage source
2. Current-dependent voltage source
3. Voltage-dependent current source
4. Current-dependent current source
Such sources can also be either constant sources or time-varying sources. Such sources are often met in electronic circuits. As seen above, the voltage or current source is dependent on the and is proportional to another current or voltage. The constants of proportionality are written as a, r, g and β. The constants a and β have no units, r has the unit of ohms and g has the unit of siemens.
Independent sources actually exist as physical entities such as a battery, a d.c. generator and an alternator etc. But dependent sources are parts of models that are used to represent electrical properties of electronic devices such as operational amplifiers and transistors etc.
Read article – Units of Resistivity
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