After the discovery of electricity, it began to be widely used in industry, although research on its nature continued. The basic laws were established that made it possible to calculate the simplest elements of the chain using Ohm's law. But complex electric circuits had already begun to appear, and often difficulties arose with their calculations. At this time, thanks to the works of the German physicist Kirgoff, the law of Kirgof appeared, which allowed to describe any electrical circuit.
Here it is necessary to make preliminary explanations on some elements of the circuit. In an electrical circuit, a node is a connection together of several (usually three or more) conductors, suitable from different places and after connecting diverging to other points. For an electrical circuit, a loop is a closed path through which an electric current passes . The circuit consists of several independent nodes, and each node occurs no more than once.
These laws have become a working tool for many generations of engineers, allowing you to solve the most complex problems. They concern primarily branched chains. The first law of Kirgoff states that the total current flowing into a node is equal to the sum of the currents flowing from it. Here you can draw an analogy with water. If two rivers join together, then the amount of water flowing through both rivers is equal to the amount of water flowing further after the confluence of the rivers.
In principle, everything is clear and understandable here. You just need to remember the law of conservation of energy. Kirghoff's law formulated above can be considered its consequence. How many electrons have come to the node of the chain, the same number of electrons must go. If all the current flowing into the node of the electric circuit does not completely leave the node, then the accumulation of charge will begin to occur in the node, but this does not actually happen. Everything is fully consistent with the current law of conservation of energy - nothing arises from anywhere and does not disappear to nowhere.
No less simple to understand and the second law of Kirgoff. It relates to complex, branched chains consisting of several elements. Such a circuit can be divided into a number of separate simple contours. If there are additional sources in the circuit, for example, a battery, then the electrons flowing in the circuit can receive additional energy or lose it on resistances and other elements.
Describing the behavior of the electric current in such circuits, the second law of Kirgoff states that in an electric circuit in a closed circuit, the sum of the EMF is equal to the total voltage drop in the circuit, i.e. the sum of the stresses in the closed loop is zero. Given the law of conservation of energy, everything is clear here too. In a closed circuit, energy cannot come from anywhere, except from an existing source. If energy is taken from nowhere, then we can talk about creating a perpetual motion machine. In this case, the current, passing through a closed circuit, will have to increase. In reality, nothing like this happens, as there is no perpetual motion machine.
Apply the laws of Kirgoff, both the first and second, for calculating the elements of chains. First of all, for calculating the operating modes and determining the necessary values of the circuit elements. These elements can be connected in different ways, forming nodes and contours. Compounds can be either sequential or parallel.
Thanks to the laws described, it is always possible to determine the operating modes of various elements, the voltages acting on them, the currents flowing, and the selection of electrical and radio products that are suitable for the operating conditions. Engineers often use these laws when calculating a wide variety of electronic and electrical circuits. This calculation allows you to ensure the correct and durable operation of the products.
This is what the laws of Kirgof are, the first and second. This is a simplified statement, formulas and possible examples of calculations are not given here, but the essence of the laws themselves is given, their relationship with the law of conservation of energy is shown, and examples of possible use are given.