• The ideal voltage source and current source are shown in figure 1.2

• Fig. 1.2

1. ideal DC voltage source

2. ideal DC current source 

3. practical voltage source

4. practical current source

• A voltage source is said to be idle if the output terminals are open such that i=0. A current source is said to be idle when the output terminals are shorted together with the voltage v=0. A non-ideal voltage source has series resistance and a non-ideal current source has parallel resistance.

Dependent or Controlled Sources:

• The ideal voltage source and current source are shown in figure 1.3. The voltage or current source whose value is not fixed but is dependent on a voltage or current at some other location in the network is known as dependent or controlled sources. There are four basic types of controlled sources.

• Fig.

1. Voltage Controlled Voltage Source (VCVS)

2. Voltage Controlled Current Source (VCVS) 

3. Current Controlled Voltage Source (CCVS)

4. Current Controlled Current Source (CCCS)

Ohms Law

• George Simon Ohm (1789 - 1854), found the relationship between voltage and current as expressed below.

   and              (6)

• Where V is the voltage in volts (V), I is the current in Amperes (A), R is the resistance in ohms (Ω) and G is the conductance in Siemens (S).