Electricity & Megnetism

Average power of electric current

We know that electric current is nothing more than the orderly flow of electric charges in a conductor of electricity. The electric current that reaches our homes is called alternating electric current. This type of electric current is generated through electromagnetic induction.

Generally, instead of using maximum values ​​of electromotive force and electric current intensity, we use the so-called effective values ​​of electromotive force and alternating current, defined in the paragraph above.

In physics, we call the effective value of an alternating electric current the intensity i ef  of a constant and direct electric current that dissipates the same amount of energy, in a time interval equal to the period T , that an alternating electric current dissipates when it passes through the same resistor.

We can show that both the effective electromotive force (or effective electric voltage) and the effective electric current intensity are related to the maximum values ​​through the following equations:

When we say that the electrical voltage between the terminals of an outlet in the city of Goiânia is 220 V, we are actually saying that the effective value of this electrical voltage is exactly 220 V. Therefore, the maximum value of the electrical voltage at this outlet is equal to:

The average power ( Avg Pot ) dissipated in a resistor, when traversed by an alternating electric current, is defined as the energy dissipated in a period divided by the period itself. Mathematically, we have:


We have:

In the above equation we have:

ef is the effective electric current through the resistor

U ef  is the effective voltage between the ends of the resistor

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