Understanding electrical circuit and its elements

Scientific and technological progress requires the continuous introduction of increasingly sophisticated technologies using electrical components. A vivid example of the developments of today are mobile phones or multifunctional portable computers. All these devices are built upon a basic electrical circuits, which is what I am sharing with you today.

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A Basic Electrical Circuit

An electrical circuit is a collection of various devices connected in a specific pattern that provides a path for the flow of electrical current. What are it's basic elements?

In principle, elements of the electrical circuit are: current source, load and conductors. The simplest electrical circuit is shown in Figure A.

Figure A. The simplest electrical circuit. Image source: wikimedia commons

Note here that the composition of the electrical circuit may include other elements, as well as switching devices, protection devices.

As we know, for the emergence of current it is necessary to connect two points, one of which has an excess of electrons in comparison with the other. In other words, it is necessary to create a potential difference between these two given points. Now for creating a potential difference in the circuit, a current source is used. The source of current in the electrical circuit can be various devices such as solar cells, generators, batteries, chemical elements, etc.

Any consumer of electric power is considered to be a load in an electrical circuit. The load exerts resistance to the electric current and the magnitude of the flowing current depends on the value of the load resistance. Current from the source of current to the load flows through the conductors. As conductors try to use materials which have the least resistance (copper, silver, gold).

It is important that in order to current to flow in the circuit, the circuit must be closed!

Types of electrical circuits

When there are two or more electrical devices present in a circuit with an energy source, there are a couple of basic means by which to connect them. In electrical engineering, the following electrical circuits exist depending upon the type of connection of electrical circuit elements:

1. a series of electrical circuits;
2. parallel electric circuit;
3. series-parallel electric circuit.

Series and parallel resistor configurations have very different electrical properties. While the third type, series-parallel circuit utilize both properties.

Sequential electric circuit.

In the series electrical circuit (Figure B.), all the elements of the circuit are in series with each other, that is, the end of the first with the beginning of the second, the end of the second with the beginning of the first, and so on. The defining characteristic of a series circuit is that there is only one path for electrons to flow.

Figure B. Serial electrical circuit. Image source: wikimedia commons

With this connection of the circuit elements, the current has only one path from the current source to the load. In this case, the total current of the circuit I, will be equal to the current through each element of the circuit:

I_tot = I1

when connected in series, the current is equal to the sum of the currents. It is the same all over the chain.
There is the same current, it is simply shown in this case as the current of each of the loads, which is the same and common for the whole section of the circuit.

The voltage drop along the entire circuit, that is, in section AB (Ua-b), will be equal to the voltage E applied to this section and is equal to the sum of the voltage drops on all sections of the circuit (resistors):

E_tot = Ua-b = E1 + E2

Parallel electrical circuit.

In a parallel electrical circuit (Figure C.), all elements are connected in such a way that their beginning is connected to one common point, and the ends to the other. In a purely parallel circuit, there are never more than two sets of electrically common points, no matter how many components are connected. There are many paths for electrons to flow, but only one voltage across all components.

Figure C. Parallel electrical circuit.Image source: wikimedia commons

In this case, the current has several paths from the source to the loads, and the total current of the circuit I will be equal to the sum of the currents of the parallel branches:

I = I1 + I2

The voltage drop across all resistors will be equal to the applied voltage to the section with parallel connection of the resistors:

U₀ = U₁ = U₂

A series-parallel electrical circuit.

A series-parallel electrical circuit is a combination of a series and a parallel circuit, that is, its elements are switched on in series and in parallel (Figure D).

Figure D. Sequential parallel electrical circuit. Image source: wikimedia commons

Conclusion

We can clearly see the difference;

• In a series circuit, all components are connected end-to-end, forming a single path for electrons to flow.
• In a parallel circuit, all components are connected across each other, forming exactly two sets of electrically common points.
  We also saw that a sequential parallel circuit is a combination of these two types of circuits.

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References for Further Reading

• Topology electrical circuits

• Resistors in Series and Parallel

• Two Types of Connections

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