Parallel circuit

Among the ways of distributing electrical energy, the parallel circuit is the most widely used standard, since it is present in most homes and appliances, but it is also used on a large scale to supply energy in large cities, for what it is worth. worth reviewing what it is and how it works.

We could say that a parallel electrical circuit is an interconnection of electrical components, where the input and output terminals of all the devices that are connected coincide with each other. In other words, it is a configuration in which an electric current is distributed in various branches, but the generators, capacitors and other elements are connected in parallel: positive with positive and negative with negative.

Thanks to the parallel connection, each device receives exactly the same voltage throughout the entire scheme. This is why parallel circuits are widely used in our homes, in order to maintain voltage on all loads, so that the failure of one element does not affect the rest. Surely you have noticed that when the light bulb in the room burns out, the one in the bathroom continues to work perfectly and vice versa. But this happens with all kinds of products, from Christmas lights, to electronic devices, for example, an Awesafe car GPS can have this type of system, but also a portable soldering iron and even toys that work with several batteries.

Main characteristics of parallel circuits

Because it is a parallel connection, this type of circuit has certain properties that differentiate it from other schemes, for this reason, it is good to analyze in more detail some of the characteristics that arise from the general definition.

All terminals connected in parallel have the same voltage

Harnessing voltage in parallel is one of the benefits of this electrical circuit. As we have seen, even if we have many elements connected, they will all have access to the same voltage level, therefore, the voltage between vertical nodes does not vary. This is why the equation used in electrical circuit exercises of this type is: Vt = V1 = V2 = V3 = … = Vn. That is, the total voltage (Vt) is equal to the voltage at any point in the configuration.

In this sense, if we connect batteries in parallel, the voltage level between nodes is maintained, as long as we make a correct connection, which is why the positive with positive and negative with negative polarity is of great importance. In this way, it is possible to connect several bulbs to a switch and, although they are different, each one can provide its maximum capacity. 

The intensity is calculated by adding the branch currents

In such a system, the flow of electrical charge is divided among the nodes in the configuration. Therefore, to obtain the total parallel current (It), all the branch currents must be added, which is why the formula to calculate the current intensity in one of these circuits is It = I1 + I2 + I3 + … + In.

The greater the number of resistors, the lower the total resistance of the system.

If we add the inverse of all the resistances in parallel, we can obtain the inverse of the total resistance of the system. In this case, the greater the number of resistors connected to the circuit, the lower the total equivalent resistance and, conversely, if the number of resistors decreases, then the intensity of the current increases. For this reason, the algebraic expression for the sum of resistances in parallel is as follows: 1/RT = 1/R1 + 1/R2 + 1/ R3… +1/ Rn.

In this way, if we want to calculate 2 resistors in parallel, we have to find the total equivalent resistance (Req), for example, we could say that R1 = 30Ω and R2 = 20Ω. Therefore, it would be like this:

1/Req = 1/30 + 1/20

1/Req = 2/60 + 3/60

1/Req = 5/60

Req = 60/5

Req = 12 Ω

Operation of a parallel circuit 

The parallel circuit is responsible for providing electrical energy in a system through the use of one or more sources connected in parallel, as in the case of the cells or batteries that we have mentioned. In this way, the electrical voltage circulates throughout the circuit, crossing the nodes through the different branches, according to the energy needs of the devices connected to each branch.

In this sense, one of the advantages of this type of circuit is that it is a robust and reliable configuration, since if there is an adequate power source, the branches can be in constant operation, even if one of them is disconnected or has some fault. For this reason, these circuits are not only used to distribute energy in the house and connect light bulbs in parallel, but also have great performance in more complex applications, where backup mechanisms are necessary so that the general operation of the system is guaranteed even if it happens. any eventuality. In this way, it is also easier to activate and disconnect each branch of the circuit independently.

What are the differences compared to a series circuit?

In a series circuit, the current has a single path and reaches all the connected terminals in succession. As more terminals are added, the resistance increases. In this sense, series circuits work practically the opposite of parallel circuits, that is, all the elements of the circuit are traversed by the same intensity, so the total intensity is found with the formula It = I1 = I2 = …. = In. For its part, the total series resistance is calculated by adding all the resistances of the system: Rt = R1 + R2 + … + Rn. This is the main difference between series and parallel circuit.