Question: Explain Ideal And Practical Voltage & Current Source With V-I Characteristics Of Ideal And Practical Voltage And Current Source ?

### Voltage source

**Voltage source** can be classified (a)** Ideal voltage source** (b) **Practical voltage source**

#### (a) **Ideal voltage source **

**Ideal voltage source** is defined as, a source which supply a constant value of **terminal voltage** for all values of current ‘l’ drawn out from it. This is because of the fact that an **ideal voltage source** has zero** internal resistance**. Fig I(a) shows the symbol used to represent an **ideal voltage source** and Fig.1 (b) shows its **output characteristic of ideal voltage source** and **current source circuit** with **voltage source symbol**

** (b)Practical voltage source **

In a **practical** **voltage source**, the terminal voltage V_{AB} reduces with the rise in output current l. The output current ‘I’ can be increased by decreasing the **load resistance** connected across the terminal A and B (not in figure)]. This drop in voltage is because every **practical voltage source** has some **internal resistance** present in it. A **practical voltage source** can be approximated by an **ideal voltage source** with a** resistance** ‘Rs’ in series with it, where Rs is the **internal resistance**. **Voltage source circuit** or **characteristic of practical voltage source** is shown in fig. 2(a) .

From fig. 2(a),

If ‘I’ increases. then from above equation V_{AB} will decrease.

**Current Source **

**Current source can be classified as : **

(a) Ideal Current Source (b) Practical Current Source Ideal current source supply a constant value Of output current ‘ I_{L}’ for all **values of voltage** appearing across it’s terminals A and B.

However, a **practical current source** supply a reducing current for increasing values of voltage appearing across it’s terminals A and B. This happens because of the fact that like a **practical voltage source**, a **practical current source** too has an internal in it due to which it cannot give out constant current for use. This **internal resistance** is absent in an **ideal current Source**. A **practical current source** can be approximated by an **ideal current source** with a ‘R_{P}‘ in parallel with it. R_{P} is the internal resistance.

Internal of **ideal and** **practical voltage source** are shown in Fig.3(a) and Fig.3(b) respectively, Fig. 3(c) shows their **output characteristics of ideal current source** and **Ideal** **current source circuit** with **current source symbol** .

From Fig. 3(b).

If V_{AB} increases, then from above equation I_{L }will decrease.

**Conversion of Sources**

While solving complicated circuits, it is normally required to convert a current source into it’s **equivalent voltage source** and vice-versa. This can be done by using Ohm’s law. For example consider the following **current source** and sec how it’s equivalent **voltage source** is obtained. Fig(1). ** conversion of current into voltage source ** with **voltage source symbol** .

V = IR = 10 x 200 = 2000V

Rs = Rp=200 ohm

Now, consider a **voltage source** and see how it’s equivalent **voltage source** can be obtained.fig (2) shows **conversion of voltage source into current source** with **current source symbol**.

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