2.1 Introduction
If I needed to describe the distance between two cities, I could provide an answer consisting of a
single number in miles, kilometers, or some other unit of linear measurement. However, if I were to
describe how to travel from one city to another, I would have to provide more information than just
the distance between those two cities; I would also have to provide information about the direction
to travel, as well.
The kind of information that expresses a single dimension, such as linear distance, is called a
scalar quantity in mathematics. Scalar numbers are the kind of numbers you’ve used in most all of
your mathematical applications so far. The voltage produced by a battery, for example, is a scalar
quantity. So is the resistance of a piece of wire (ohms), or the current through it (amps).
However, when we begin to analyze alternating current circuits, we find that quantities of voltage,
current, and even resistance (called impedance in AC) are not the familiar one-dimensional quantities
we’re used to measuring in DC circuits. Rather, these quantities, because they’re dynamic
(alternating in direction and amplitude), possess other dimensions that must be taken into account.
Frequency and phase shift are two of these dimensions that come into play. Even with relatively
simple AC circuits, where we’re only dealing with a single frequency, we still have the dimension of
phase shift to contend with in addition to the amplitude.
2.1 IntroductionIf I needed to describe the distance between two cities, I could provide an answer consisting of asingle number in miles, kilometers, or some other unit of linear measurement. However, if I were todescribe how to travel from one city to another, I would have to provide more information than justthe distance between those two cities; I would also have to provide information about the directionto travel, as well.The kind of information that expresses a single dimension, such as linear distance, is called ascalar quantity in mathematics. Scalar numbers are the kind of numbers you’ve used in most all ofyour mathematical applications so far. The voltage produced by a battery, for example, is a scalarquantity. So is the resistance of a piece of wire (ohms), or the current through it (amps).However, when we begin to analyze alternating current circuits, we find that quantities of voltage,current, and even resistance (called impedance in AC) are not the familiar one-dimensional quantitieswe’re used to measuring in DC circuits. Rather, these quantities, because they’re dynamic(alternating in direction and amplitude), possess other dimensions that must be taken into account.Frequency and phase shift are two of these dimensions that come into play. Even with relativelysimple AC circuits, where we’re only dealing with a single frequency, we still have the dimension ofphase shift to contend with in addition to the amplitude.
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