# How is a voltage source actually created

## Voltage sources - electric power for everyday life!

### What are voltage sources and what is an electrical voltage?

In electrical engineering, an active two-pole device, i.e. a component with two connections (terminals), is referred to as a voltage source if it supplies an electrical voltage. The current strength, however, is negligible in most cases. The electrical tension in electricity is something completely different from the compressive or tensile tension in mechanics.

If two opposite charges Q of two electrically charged bodies are displaced at a distance r against the Coulomb force, a displacement work W is carried out. This work of displacement is stored in the system as potential energy. The voltage U in joules per coulomb or volt is the potential difference in the potential energy between the two distances. If one shifts an electrical elementary charge e against a voltage U of one volt, an energy contribution is necessary, the electron volt eV.

### What is the difference between a voltage source and a current source?

Like the voltage source, a current source is also an active two-terminal network, with the difference that current is supplied to these connections. In contrast to the electrical voltage, the current is a flow of charge of freely moving electrons, the conduction electrons, which migrate from the negative pole of the terminal to the positive pole. The current strength at the current source is just as little dependent on the voltage as vice versa. Ideally, it is independent of the connected consumer. Different power sources deliver:

• Direct current
• Alternating current
• Three-phase current

The circuit symbol for a current source in a circuit is a circle with a solid center line, whereas a voltage source is identified as an isosceles U with a small circle on each of the legs.

### What types of voltage sources are there?

In electrics, an ideal voltage source is independent of current and supplies either a direct voltage or an alternating voltage. Examples of voltage sources are:

• galvanic element
• battery
• Solar cell

The galvanic element, as the first artificial source of electrical energy, is a direct voltage source, which makes use of the different solubility of different materials in an electrolyte. A battery with one cell that works according to this principle supplies a DC voltage of 1.5 volts. Cells connected in series n thus supply a direct voltage of n times 1.5 volts. Alternating voltages, on the other hand, are generated with a dynamo and change periodically over time. The voltage source can also be divided into ideal and real voltage sources. An ideal voltage source supplies a constant voltage regardless of current and consumer. Real voltage sources, on the other hand, are ideal voltage sources that deliver an open circuit voltage and are influenced by the internal resistance.

### Why do voltage sources have an internal resistance?

Substances with fewer or more freely movable charge carriers are called electrical conductors and are differentiated from non-conductors or insulators. The conductor, which, when a voltage is applied, opposes the flow of electrons with an internal resistance due to friction, is dependent on the voltage that causes a charge gradient. The voltage U in volts is directly proportional to the current I in amperes and the resistance in ohms (V / A). The different resistances of materials are directly related to their specific conductivity. The specific resistance or its reciprocal value, the conductivity, are material constants which, in connection with the length and the cross section of the conductive material, result in the electrical resistance.

### What is the relationship between the voltage source and the terminal voltage?

The internal resistance is an effect that occurs with all voltage sources and lines. If the voltage value of the terminal voltage is to largely correspond to the source voltage, the internal resistance of the voltage source must be as low as possible. If, on the other hand, the resistance of the voltage source drops to zero, the voltage is zero and an electrical short-circuit current is generated. There is therefore no uniform value for the output resistance at the voltage source and it is dependent on:

• small load changes (differential resistance)
• rapid changes (dynamic internal resistance)

The maximum current of the terminal voltage is determined by the static internal resistance (statics).

### When is a circuit created?

An electrical circuit is created by connecting electrical or electromechanical components in series or in parallel. An electrical energy source is required for an electrical circuit, that is to say a power generator in the form of a voltage source or a current source. A simple circuit therefore consists of a generator and a consumer, which are coupled to one another via cables. This circuit can be interrupted by a switch.

### What is the current strength of the voltage source?

In all subjects and grade levels you learn: In order for a voltage to flow in a circuit, an electrical voltage, the power source, must be present. In electronics, however, a distinction is made between voltage source and current source. The following applies here:

1. An ideal voltage source supplies a constant voltage, regardless of the value of the current strength.
2. An ideal power source always delivers the same amperage. The voltage required for this is automatically regulated by the power source.

These are idealized model types. In fact, the voltage drops when loaded with higher currents.