Electric power: What is and how is calculated
Do you want to know how electric power is calculated? In our guide, you will learn the power formula, practical examples and much more.
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Understanding the electrical power and how it is calculated is essential for Promote efficient energy use and minimize environmental impact. Is that, with the immense dependence on technology and electricity in our life, the knowledge of these Concepts becomes a valuable tool for consumers and professionals in the sector Electric The proper management of electrical power contributes not only to the optimization of resources, but also to long -term sustainability!
1 Meaning of electrical power
We all ever hear about "electrical power" but, do we really know what it is? As fundamental concept in the field of electricity, electrical power plays a role crucial in our daily lives and in the functioning of numerous devices and systems.
Electrical power is defined as the speed with which work is done or transferred energy in an electrical circuit. In other words, it represents the amount of energy that consumes or It supplies an electrical device over a certain period of time.
2 Types of power
Deepening this guide, we must take into account that the electrical power is classified into two Types: Active (or real) power and reactive power. The active power is the one that really performs useful work, while reactive power is related to energy transfer between inductive and capacitive components of the circuit, without doing direct work.
What better than deepening examples? Active power is the spark that drives actions direct and useful, such as lighting a light or moving a vehicle, while the reactive power is more related to temporary energy storage, ready to be used on devices than They need a momentary impulse without doing a direct job at that time.
3 Electric power formulas
In this section we are forced to get mathematical, but do not be scared, then we will take it to practice with more practical examples. The first fact that you have to know is that the unit of Measurement of power in the international system is the watt (W).
The calculation of electrical power is based on OHM's law and Joule's law. The formula fundamental to calculate the power (P) is:
where:
- P is the power in watts (W).
- V is the potential or voltage difference in volts (V).
- I is the current in amps (a).
- cos (θ) is the power factor, which indicates the efficiency in energy conversion.
In direct current circuits (CC), the calculation is easier, since the factor is not considered of power
The formula is simplified to:
P = V⋅I
In the case of alternating current (CA) circuits, both active power must be taken into account Like reactive.
The total power is expressed as:
S = P+JQ
where:
- S It is the apparent power in voltial (VA).
- P is the active power in watts (W).
- Q is reactive power in reactive voltial (VAR).
- J is the imaginary unit.
Remember that optimizing power factor is essential to improve energy efficiency and Reduce losses in the electrical system!
4 Practical examples
Electric power in the Light Invoice
To calculate the electric power on the light invoice, we would need to know both the consumption of Electricity (expressed in kilowatts-Hora, KWH) as the contracted power (expressed in kilowatts, kW). The contracted power is the maximum amount of energy that can be consumed simultaneously in a home or business and is established when hiring the electrical service with the supply company. Suppose in your light bill, you have consumed a total of 300 kWh During the month. In addition, the power hired for your home is 5 kW. To calculate the power Medium electric (or active power), we can use the formula:
| Electrical power (kW) = | Energy consumption (kWh) |
| Hours in the month |
It is important to keep in mind that the result will be in kilowatts (kW). If we assume there are 30 days In the month and that every day it has approximately 24 hours, we can calculate the electrical power of The following way:
| Electrical power (kW) = | 300 kWh |
| 30 days x 24 hours/day |
| Electrical power (kW) = | 300 kWh |
| 720 |
| Electrical power (kW) = | 0.4167 kW |
So, the average electrical power in your home is approximately 0.4167 kW.
Now, to verify if the contracted power is sufficient, we can compare it with the power 5 kW hired. In this case, the contracted power is more than enough to cover your Average demand, since 0.4167 kW is significantly lower than the contracted power of 5 kW.
Electrical power in everyday devices
We are going to imagine a simple scenario in which we want to calculate the electrical power used For a lamp in a home. For this, we need to know two key factors: voltage (v) to that operates the lamp and the current (i) that flows through it.
Suppose the lamp works at 120 volts and the current that passes through it is 1.5 amps. As we already saw in the previous section, to calculate the active (real) power, We use the formula:
P = V⋅I
P = 120V⋅1.5a
P = 180W
The active power of the lamp is 180 watts. This means that the lamp consumes 180 watts of electric power while it is lit.
Now, suppose we want to take into account the apparent power, which includes both power active as the reactive. Suppose that, in this case, the power factor (cos (θ)) is 0.9. The Formula for apparent power (s) is:
S = p/cos (θ)
We replace the known values:
S = 180W/0.9
S = 200va
Then, the apparent power of the lamp is 200 voltial. This figure includes both the active energy such as reactive and gives us a more complete image of the electrical performance of the lamp in the circuit.
Keep in mind that this practical example illustrates how to calculate electric power on a device simple, taking into account both active and apparent power. You can keep inventing situations and calculating the power.