Perhaps the most familiar source of DC voltage is a battery. AC circuits are a bit more complicated and will be discussed later in this chapter. “DC” and “AC” are sometimes attached to the word “current,” even though these phrases mean “direct-current current” and “alternating-current current.” The bottom line is that “DC” and “AC” are no longer exact equivalents for “direct current” and “alternating current” DC refers in a general way to quantities that don’t regularly change polarity or that have very low frequency, and AC refers in a general way to quantities that regularly change polarity at a frequency that is not “very low” in the context of a given system.įor now, we’ll focus on DC circuits. A DC voltage is a voltage that produces, or would produce, DC current, and an AC voltage produces or would produce AC current-and this introduces another terminology problem.
This can be a bit confusing at first: what is a direct-current voltage or an alternating-current voltage? This is not the best terminology, but it is completely standard. The terms “DC” and “AC” have become adjectives that are frequently used to describe a voltage.
This is in contrast to alternating current (AC), which regularly changes direction and is used all over the world for the distribution of electrical power. The most fundamental characteristic of direct current, though, is the following: it does not regularly change direction. There are two common ways of transferring electrical energy: direct current and alternating current.ĭirect current (DC) can increase or decrease in all sorts of ways, but the magnitude of the changes is usually small with respect to the average value. Two Common Types of Voltage: Direct and Alternating Current We simply want to design a functional circuit, and consequently, we think in terms of how much power is lost (i.e., dissipated) or used (i.e., consumed). However, in most cases, we are not intending to transfer energy. We don’t say “transferred” because, in general, the final state or location of the energy is not important.įor example, if the voltage across a resistor is 5 V and the current through the resistor is 0.5 A, the resistor is transferring 2.5 W of power (as heat) to the surrounding environment. When we are analyzing circuits, we typically discuss power using the term “dissipated” or “consumed” instead of “transferred.” This emphasizes the fact that the power leaves the electrical system or is used by an electrical component. On the right side of the equation, the two “coulomb” terms cancel out, and we are left with joules per second. The unit is watts (W), where one watt is equal to the transfer of one joule (J) of energy in one second (s).Įlectric power in watts is equal to voltage in volts multiplied by current in amperes. Electrical power, then, is the rate at which electrical energy is transferred. In a scientific context, power refers to the rate at which energy is transferred. Power in Electronics and How its Calculated Voltages are the same across all components It is astonishing to think of the diverse and sophisticated functionality that begins with electrical energy that can be transferred through two small copper wires. If these two points are connected by a conductive material, electrons will naturally move from the lower voltage to the higher voltage this movement is called electric current, denoted by I.Įlectricity is a particularly convenient and versatile form of energy, and this has made it a powerful tool in the hands of the countless clever individuals who have designed everything from large electrical equipment to tiny electronic devices. When the accumulation of electrons creates a difference in electric potential energy between two points, we have a voltage (in equations, voltage is denoted by V). The various forms of energy-thermal, mechanical, chemical, etc.-are manifestations of a fundamental entity that results in physical change as it is transferred from one object to another.Įlectricity is a form of energy that results from the existence and movement of charged particles called electrons. This abundance of perpetual activity is bound to the concept of energy. Objects are moving, chemical reactions are taking place, temperatures are increasing and decreasing.
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