5 Interesting Facts about Voltage Sources (Only Few People Know)


An electrical circuit has several elements with different functions. Among the most essential elements is voltage sources that deliver electric power. In fact, there are two types of electrical sources: voltage and current source. But here, you are about to know more about voltage source, its function and types.

This kind of source is most commonly used in electrical networks. The two-terminal device delivers continuous force to move the electrons through the network’s wire. Here are some interesting facts about voltage source you need to know.

Voltage Sources

Voltage Source Definition

A voltage source can be defined as a two-terminal device that delivers or generates electric power into a connected network. The source can also maintain fixed voltage that does not change. This kind of electrical source can be categorized as direct source (DC) or alternating source (AC).

The constant voltage delivered by the device is called as a DC voltage while the voltage that varies is called as an AC voltage. In everyday practices, batteries are the real example of DC sources and the wall socket is the example of AC source.

In fact, voltage source is a passive element which can convert thermal, chemical, mechanical, or other forms of energy into electrical energy. For instance, chemical energy is converted into electrical energy by a battery. Or else, mechanical energy is converted into electrical energy by a DC generator.

As time goes by, innovative technology can convert other energy sources into electrical energy. Sophisticated devices can convert energy from renewable sources such as waves, wind, heat, and sun into electrical energy.

Types of Voltage Source

There are two types of voltage sources, namely independent and dependent sources. Each type is divided into two other types, each of which comes with different characteristics. Figure out each kind of voltage source below.

Independent voltage source

This source refers to a device that can deliver steady voltages to the AC or DC circuits. As the name implies, this source does not depend on other elements in the circuit. This type of source is divided into two types, direct source (DC) and alternating source (AC).

The direct source can produce constant voltage as the electrons flow in one direction. For this reason, the voltage value will not change. Battery and DC generator are the example of this direct voltage source.

Meanwhile, alternating source can deliver alternating voltage. At regular intervals, the polarity get reversed and cause the current flows in different direction from time to time.

Dependent voltage source

Dependent Voltage Source Symbols

Dependent voltage sources are devices that can deliver unsteady output voltage. Additionally, it depends on other elements in the circuit such as the voltage or current in other part of the network. This voltage source is divided into two types: voltage controlled and current controlled voltage source.

The voltage controlled is when the source depends on voltage of other part of the circuit. But when it depends on the current of other part of the circuit, it is referred to as current controlled.

Ideal vs Practical Voltage Sources

Ideal and Practical Voltage Source

An ideal voltage source can be described as a 2-terminal active element which can supply and maintain constant voltage across the terminals. This voltage source is also known as independent source since it does not depend other elements in the circuit.

Another important point about ideal voltage sources is the internal resistance value that should be zero. That means the device can perform efficiently up to 100 percent. The example of ideal voltage source is automobile battery that offers constant voltage and delivers power in one direction.

Meanwhile, practical voltage source has a small voltage drop so the output voltage reduces. In practices, internal resistance can also reduce the voltage. Fortunately, the internal resistance can be minimized to reduce the power loss. Therefore, the real voltage source can be close to the ideal one.

In fact, there is no ideal voltage source in everyday practices. All sources have internal resistance as well as non-zero impedance. And yet, practical voltage can be modeled in a linear circuit analysis by combining ideal voltage source with non-zero resistance in series.

Connecting Voltage Sources

Voltage sources, particularly the ideal ones, can be connected one another. The connection can be in parallel or series, with series voltages are added together while voltage in parallel should be in the same value. Unequal voltage sources are not possible to be connected in parallel.

Voltage source in series

Voltage Source in Series

Ideal voltage source can be connected in series with connected polarities. In series aiding sources, the plus terminal voltage must be connected to the negative terminal, allowing the current to flow similarly. Meanwhile, series opposing sources come with plus or negative terminals are connected one another.

To find the value, larger voltage is subtracted by the smaller voltage. That means when the series opposing sources come with the same voltages, the voltage value will be zero.

Voltage source in parallel

Even though it is not best practice, the sources can be connected in parallel in a specific condition—the voltage must be in the same value. When you need to connect ideal sources with different voltage value, it is not possible to do in parallel configuration. Even star delta transformation cannot help.

Voltage Source vs Current Source

Some people use voltage and current sources interchangeably while some others consider that both of them are different electrical sources. You can never find the truth before comparing one another.

Most electrical energy sources are considered voltage sources. The ideal source does not provide energy when loaded by open circuit, but it delivers almost infinite energy as well as current when its load resistance nearly reaches zero.

Meanwhile, current sources deliver constant currents as long as the connected load has low impedance. The ideal source does not provide energy to a short circuit. Additionally, it delivers almost infinite energy when the load resistance nearly reaches infinity. In real practices, no ideal sources really exist as most sources have non-zero and finite impedance. For this reason, voltage sources can be considered as current sources and vice versa. Both of them are often called duals as they can be converted into one another using Thevenin’s or Norton’s theorem.

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