Why Alternating and Not Direct?
Do you wonder why ac is used at all? Isn’t it a lot more complicated than dc? Well, ac may be more complicated in theory, but in practice it is a lot simpler to...
Category: Alternating-Current Basics
Alternating-Current Basics
The Generator
Alternating current can be generated by a rotating coil of wire inside a powerful magnet, as shown in above Figure. An ac voltage appears between the ends of the wire coil. The ac voltage...
Expressions of Amplitude
Amplitude is also called magnitude, level, strength, or intensity. Depending on the quantity being measured, the amplitude of an ac wave can be specified in amperes (for current), volts (for voltage), or watts (for...
Fractions of a Cycle
Engineers break the ac cycle down into small parts for analysis and reference. One complete cycle can be compared to a single revolution around a circle. Degrees One method of specifying the phase of...
Frequency Spectrum
An oscilloscope shows a graph of amplitude as a function of time. Because time is on the horizontal axis and represents the independent variable or domain of the function, the oscilloscope is said to...
Complex and Irregular Waveforms
As long as a wave has a definite period, and as long as the polarity keeps switching back and forth between positive and negative, it is ac, no matter how complicated the actual shape...
Sawtooth Waves
Some ac waves rise and/or fall in straight, sloping lines as seen on an oscilloscope screen. The slope of the line indicates how fast the magnitude is changing. Such waves are called sawtooth waves...
Square Waves
On an oscilloscope, a square wave looks like a pair of parallel, dashed lines, one with positive polarity and the other with negative polarity (Following Fig. A). The oscilloscope shows a graph of voltage...
The Sine Wave
A sine wave. The period is the length of time it takes for one cycle to be completed. Sometimes, alternating current has a sine-wave, or sinusoidal, nature. This means that the direction of the...
Period and Frequency
In a periodic ac wave, the kind that is discussed in these topics (and throughout the rest of this book), the function of instantaneous amplitude versus time repeats itself over and over, so that...
Alternating Current
In ac, the polarity reverses at regular intervals. The instantaneous amplitude (that is, the amplitude at any given instant in time) of ac usually varies because of the repeated reversal of polarity. But there...