Calculation of Stress, how to do?

When it comes to electrical energy, electricity and the like, the term electrical voltage is very common, after all it is one of the fundamental electrical quantities for any electrical or electronic equipment and its values ​​are considered from the beginning of the projects until their execution. It is extremely important to know the nominal values ​​of the electrical voltage to design conductors, transformers and circuit breakers for example.

What is the electrical voltage?

DDP (potential difference) also known as the electrical voltage is the difference in electrical potential between two points, that is, it is the force that drives free electrons, consequently generating the electric current. Electrical voltage can also be understood as the amount of energy generated to move an electrical charge.

To better understand what electrical tension is, we will use as an example a tire on a wooden surface, where the tire represents the electric current and the slope of the wood is the electrical tension.

At this moment the wood is on a straight surface with its edges levelled, in that case, there is no difference in height between the ends of the wood, so the tire will remain stationary at the same point. This means that the difference in gravitational potential between the ends is equal to zero, that is, there will be no tire passing through the surface of the wood.

Potential difference is zero.

Now imagine that one of these ends of the wood has been suspended and its ends are not level, so we have a higher end of the wood that you hear, causing the tire to move out of its point of origin. Now we have a difference in gravitational potential between the ends of the wood, causing the tire to leave its point of origin. The difference between the upper and lower ends of the wood is an analogy to the difference in electrical potential that exists in a circuit.

The potential difference between two points.

Voltage Drop

The voltage drop is an irregularity caused both by the distances travelled by the electric current in an electrical circuit and the demand for electrical voltage by the circuit components. Another factor that influences the voltage drop is the inductive reactance, caused by non-resistive loads. However, it is considered for small consumers and small loads that the electric current is distributed evenly among the conductors despite the generated magnetic field.

According to NBR 5410, we must pay attention to the dimensioning for factors such as the voltage drop in the conductors, in such a way that precautions must be taken to prevent a voltage drop or a total lack of electrical voltage, associated or not with the subsequent one. restoration of electrical power will present danger to people or damage to part of the installation, equipment for use and goods in general.

Visual demonstration of electrical voltage drop:

In the figure below we have a 9V battery that provides electrical power to the circuit, allowing the LED of approximately 2V and 20mA to light. In this example, the 350 ohm resistor is a resistive element, responsible for the voltage drop, to prevent the LED from being damaged. When electrical current passes through the resistor, the LED lights up, thus demanding an amount of electrical voltage that the battery must be able to supply.

Note that in the batteries there are signs of (+) and one of (-), which represent the potential difference, where the (+) represents a greater electrical potential in relation to the other pole of the battery, and the Higher potential is where the electric current comes from the source. The (-) pole of the battery represents a lower potential, which is where the electric current returns, thus making a cycle, which in this case remains until the source discharges and cannot support providing more electrical energy for the load.

Serial circuit, battery and LED.

The circuit above is a series circuit, as it is a circuit whose components are connected sequentially in a single loop. The electric current flows through the entire circuit, passing through each resistor or element in sequence, that is, the electric current is the same at all points in the circuit.

One way to calculate the electrical voltage drop caused by the resistor so as not to damage the LED is by applying the ohm law. Knowing that the maximum electrical current that can flow throughout the circuit is 20mA and the resistance of the resistor is 350 ohms it is possible to calculate the potential difference in the resistor.

Ohm’s law, electrical voltage drop.

The voltage drop caused by the resistor was 7V, thus maintaining the integrity of the LED, leaving only 2V to supply it.

In the case of parallel circuits it is a little different, as we can see the circuit diagram in the image below.

Demonstration of the parallel circuit.

The analysis for electrical voltage is even simpler, because the electrical voltage that the resistors (loads) “see” is the same as the nominal electrical voltage of the battery, so they have the same value, because all the loads are connected to the same points. There are also some formulas for finding the value of the electrical voltage, which will depend on each analysis.

In addition to the series and parallel circuits, we have the mixed circuit, which is the junction of the series and parallel circuit, as we can see in the image illustrated below:

Mixed circuit connecting LED’s.

The resistor is in series with the LED and there are three associations of LEDs with resistors that are in parallel with each other and also parallel with the battery, featuring a parallel series association circuit.

Formulas for calculating electrical voltage:

An electric field resulting from the interaction of the charges present in the batteries when interacting with the charges in the conductors causes the movement of these charges, which are configured in a flow which originates the electric current. Thus, it can be concluded that the electrical voltage is analogous to the amount of energy that a generator provides to move an electrical charge through a conductor.

This concept allows us to understand the formula below:

Calculation of the electric voltage in relation to the electric field and the load.

Ohm’s Law

There is a very simple relationship between electrical current, electrical voltage and resistance. Write this formula down on paper to memorize it, as you will need it to solve problems related to various electrical calculations:

Ohm’s law in the calculation of electrical voltage.

It is also possible to calculate electrical voltage through electrical power, as we can see in the image below:

Method of calculating the electrical voltage.

Kirchhoff’s Second Law

In Kirchhoff’s second law he says that in a mesh, the sum of the electrical tension is always equal to zero. The loop is all closed circuit through which an electric current flows, in some cases a circuit may have more than one loop and using the ohm law with Kirchhoff’s second law it is possible to determine the current that passes through a given loop and voltage drops in loads.

Analysis of a series circuit.

The above equations are some of the ways that make it possible to calculate this quantity (electrical voltage). There are even more possibilities, we must evaluate the problem we have and choose which form is the one that best suits the calculation process and thus find the value of the electrical voltage.