A voltage source establishes and maintains an electrical potential difference, or voltage, between two points in a circuit. This potential difference provides the energy to drive electric current. In electronics, the “ideal voltage source” is a theoretical model. It simplifies complex electrical systems, helping engineers and students grasp underlying principles. This construct represents a perfect version of a real-world power supply, used primarily for analysis rather than as a physical device.
What Makes a Voltage Source Ideal?
An ideal voltage source possesses specific characteristics. Its defining feature is its ability to deliver a constant voltage across its terminals, irrespective of the current drawn by a connected load. This means the output voltage remains fixed, whether the circuit demands a small current or a large one.
This consistent voltage output is possible because an ideal voltage source has zero internal resistance. In a real source, internal resistance causes some voltage to drop within the source as current flows, leading to a reduced terminal voltage. With zero internal resistance, an ideal source ensures the entire generated voltage is available at its terminals, allowing it to supply current without internal voltage loss.
The Difference Between Ideal and Real
Real-world voltage sources, such as batteries, generators, or power supplies, differ from their ideal counterparts due to internal resistance. This internal resistance is an inherent property of the physical materials and electrochemical processes within the source. It acts like a resistor connected in series with the ideal voltage source model.
When current flows from a real voltage source to a connected load, a portion of the voltage is dropped across this internal resistance, following Ohm’s Law. Consequently, the voltage measured at the terminals of a real source decreases as the current drawn from it increases. For example, a battery’s voltage might drop when a high-power device is connected. This voltage reduction becomes more noticeable with higher internal resistance or greater current demand.
The internal resistance of a battery, for instance, can be influenced by factors like its chemistry, age, temperature, and state of charge. A fresh AA alkaline battery might have an internal resistance ranging from 0.1 to 0.9 Ohms. As a battery discharges or ages, its internal resistance increases, leading to a more pronounced voltage drop under load and a reduced ability to deliver power efficiently.
Why We Use Ideal Models
Ideal voltage source models are valuable tools in electrical engineering and circuit design. They simplify the complex behavior of real-world components, making it easier to analyze and understand fundamental circuit operations. By starting with simplified models, engineers can focus on the core principles of how circuits function without being overwhelmed by real-world imperfections.
This simplification allows for quicker calculations and a clearer understanding of circuit responses. The ideal model serves as a building block for advanced analysis. Once the basic circuit behavior is understood using ideal components, real-world factors like internal resistance can be introduced to refine the analysis and predict actual performance.