- Voltage Source Definition: A voltage source is defined as a device that delivers electric power to a connected circuit.
- Independent Voltage Source: Delivers a steady voltage and does not depend on other circuit elements.
- Direct and Alternating Voltage Sources: Direct voltage sources provide constant output, while alternating voltage sources change polarity at intervals.
- Dependent Voltage Source: The output depends on other quantities in the circuit, such as voltage or current elsewhere.
- Ideal vs. Real Voltage Source: Ideal sources have no internal resistance and are 100% efficient, whereas real sources have internal resistance, causing minor voltage drops.
What is a Voltage Source?
A voltage source is defined as a device that delivers electric power to a connected circuit. Simply put, it pushes electrons through a wire, similar to how a pump moves water. Voltage sources power many electrical devices and systems.
A voltage source usually comes as a two-terminal device, meaning it has two points for connection – one for the incoming electrons and one for the outgoing. This concept forms the backbone of our day-to-day electricity usage, powering everything from your mobile phone to your kitchen appliances.
Types of Voltage Sources
The main types of voltage sources include:
- Independent Voltage Source: They are of two subtypes – Direct Voltage Source and Alternating Voltage Source.
- Dependent Voltage Source: They are of two subtypes – Voltage Controlled Voltage Source and Current Controlled Voltage Source.
Independent Voltage Source
An independent voltage source provides a steady voltage, either fixed or variable, and does not rely on other circuit elements.
Direct Voltage Source or Time Invariant Voltage Source
The voltage source which can produce or deliver constant voltage as output is termed as Direct Voltage Source. The flow of electrons will be in one direction that is polarity will be always same. The movement of electrons or currents will be in one direction always. The value of voltage will not alter with time. Example: DC generator, battery, Cells etc.
Alternating Voltage Source
An Alternating Voltage Source produces an output that changes polarity at regular intervals. This causes the current to flow first in one direction, then in the opposite direction. Examples include DC to AC converters and alternators.
Dependent or Controlled Voltage Source
A dependent voltage source delivers an output that varies and depends on other quantities, like voltage or current, in different parts of the circuit.
They have four terminals. When the voltage source depends on voltage in any other part of the circuit, then it is called Voltage Controlled Voltage Source (VCVS).
When the voltage source depends on current in any other part of the circuit, then it is called Current Controlled Voltage Source (CCVS) (shown in the figure below).
Ideal Voltage Source
The voltage source can deliver constant voltage to the circuit and it is also referred to as an independent voltage source as it is independent of the current that the circuit draws. The value of internal resistance is zero here. That is, no power is wasted owing to internal resistance.
In spite of the load resistance or current in the circuit, this voltage source will give steady voltage. It performs as a 100% efficient voltage source. All of the voltage of the ideal voltage source can drop perfectly to the load in the circuit.
To understand an ideal voltage source, we can take an example of a circuit shown above. The battery shown here is an ideal voltage source that delivers 1.7V. The internal resistance RIN = 0Ω. The resistance load in the circuit RLOAD = 7Ω. Here, we can see the load will receive all of the 1.7V of the battery.
Real or Practical Voltage Source
Next, we can consider a circuit with a practical voltage source having an internal resistance of 1Ω in a similar circuit which is explained above. Due to the internal resistance, there will be a small amount of voltage drop in the RIN.
So, the output voltage will be reduced to 1.49V from 1.7V. So in practical cases, there will be a reduction in source voltage due to the internal resistance.
We can now conclude that the ideal voltage source is kept as model and the real voltage source is made with minimum internal resistance to get the voltage source close to the ideal one with minimum power loss.
