Any person, if he, of course, has not given up the benefits of civilization, is surrounded by many electrical devices. You don’t need to go far for examples: a TV, a telephone, the most ordinary incandescent lamp , etc. The basis of all such devices is an electric circuit. Many literary sources give similar definitions, however, with reference to the simplest variety. Why is it so, because modern electronic devices are so complex that they are trusted in computerized systems? Indeed, it is strange, especially if we recall the central processors of personal computers with their millions of transistors - they also have a direct current circuit. The reason for the above simplification of the definition is that any, even the most complex, electrical circuit can be represented in the form of a large number of simple components. By the way, that is why it becomes possible to perform the necessary calculations using well-known formulas.
So, with a simple and complex decided. Now let’s explain what an electric circuit is. In order to be more clear, consider the simplest example - an electric flashlight. And not the one in which the control chip is used (switching modes, blinking, etc.), but the most common one - with a battery, a light bulb and a toggle switch. It consists of a housing in which the light source itself , a switch, a battery compartment with two contacts are located. By inserting the battery into the housing and clicking the switch, you can achieve a bright directional glow of the lamp. Having completed these actions, we formed just what is called an electrical circuit (in a professional slang, we assembled a circuit). The current of the electric power source (battery) rushed along the path: the positive pole contact is the conductor, the toggle switch is the lamp is the negative pole. This is called the "simplest electrical circuit." In the example with a flashlight, there are three elements: an emf source, a toggle switch, and a lamp. It is worth noting that the movement of electrons (current) is possible only in a closed circuit, so if you turn off the toggle switch and break the circuit, it will disappear, although the source voltage remains. By the way, all processes can be described and calculated not only through current, but also through voltage, power, EMF.
A universal calculation tool is Ohm's law. In this case, it looks like:
I = E / (R + r),
where I - current, Amperes; E - EMF, Volts; R - bulb resistance, Ohm; r is the resistance of the emf source, Ohm. In the example used, the influence of the resistances of the conductor and the toggle switch is not taken into account, since it is negligible.
So, the electric circuit and its elements can include a power source, resistors, capacitors, inductors, semiconductor components, etc. Moreover, all this must be connected together by conductors, forming a continuous path for the passage of current.
Simple chains are divided into unbranched and branched. In the first case, the same current passes through all the constituent elements (the rule is for series connection of consumers). In the second case, one or more branches are additionally added, connected to the considered simplest circuit through nodes. In this case, a mixed connection of circuit elements is formed, so the value of the current flowing in each branch is different. Here, a branch is a section of an electric circuit, through all the elements of which the same current flows, and the opposite ends of which are connected at two nodes. Accordingly, a node is a point in an electrical circuit at which three or more branches converge. On schematic diagrams, nodes are often just designated by dots, which simplifies the perception (reading).