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1.1: Introduction

  • Page ID
    25014
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    Little Background and Perspective

    This text focuses on the analysis of DC (direct current) electrical circuits. It assumes no prior knowledge of electrical quantities, systems or circuit theory. As with any new endeavor, it is important to define the terminology and tools to be used at the outset. We shall be examining the basic electrical quantities, their relationships, proper terminology, and a variety of analysis techniques and theorems that have broad application in the field. In this regard, our analytical “tools” are the appropriate mathematics and standards, and the scientific method, which are detailed in this chapter. The definition of specific electrical quantities and their relationships begins in Chapter Two. Various analysis techniques and theorems are detailed in subsequent chapters.

    The initial research into electricity occurred in the late eighteenth and early nineteenth centuries by individuals such as Alessandro Volta, André-Marie Ampère, Michael Faraday and Georg Ohm. This work was expanded later in the nineteenth century by Gustav Kirchhoff, James Clerk Maxwell, Léon Charles Thévenin and others. The late 1800s and early 1900s saw the practical application of electrical theory to solve practical problems (i.e., the field of electrical engineering). Perhaps the two names most associated with this period are Thomas Edison and Nikola Tesla. Numerous other individuals made contributions as well, eventually leading to the age of electronics, fully coming into its own by the mid-twentieth century with the introduction of solid state devices such as the bipolar junction transistor. The pace of these developments has been quite rapid. For example, a little over a century ago the average person did not have ready access to something as simple as a modern flashlight. To put this into perspective, if we were to scale all of human history from the emergence of modern homo sapiens to today into a single year; radio, television, digital computers and all the rest would show up only within the last couple of hours before midnight on the last day of the year.

    At this point we need to distinguish between electricity and electronics. The term electricity tends to refer to the general relationships between electrical quantities such as voltage and current. In practical use, an electrical system tends to refer to a system where electrical energy is used directly to perform some manner of physical work. Examples include commercial and residential wiring systems for lighting, heating and the like. Electrical power generation and transmission would normally fall into this category, such as the high voltage transmission line seen in Figure 1.1.1 .

    clipboard_e077bb062b954462e73129fafcfdda64e.png

    Figure 1.1.1 : 345,000 volt transmission lines.

    In contrast, electronic systems, or simply electronics, tends to refer to systems where electrical signals are used to represent, store and/or manipulate some kind of information. This runs the gamut from radio and television to computing devices, cell phones, non-acoustic musical instruments, etc. Some of these applications may be obvious, where the individual interacts directly with the device such as a cell phone or tablet. On the other hand, the human interaction may be minimal such as with the engine management system of a modern car. A good example of a modern device packed with electronics is the DSLR, or Digital Single Lens Reflex camera. These devices include numerous electronic sensors and actuators to adjust to ambient light, for automatic focus, and the like. An example is shown in Figure 1.1.2 . The usage and scale of power transmission lines versus digital cameras may seem to be wildly separated but, ultimately, they are both made possible by the application of the basic laws of electrical circuit theory.

    clipboard_eb8dff7d443fef32998cee70315fa8c78.png

    Figure 1.1.2 : A digital SLR camera.

    Another good example of the shear scale of difference is to look at a single electrical device such as a DC motor. Figure 1.1.3 shows a simple DC hobby motor, the kind of device that might be used for a motorized toy. This device runs on 12 volts, as available from a battery, and draws only a few hundredths of an amp of current (to put this in perspective, the typical old-fashioned incandescent light bulb draws between one half and one amp of current from a 120 volt socket).

    clipboard_e2d6ae139ab72af2afa9b55ae4a9139c9.png

    Figure 1.1.3 : A DC hobby motor

    Compare this to the industrial DC motor seen in Figure 1.1.4 . This is a 4000 horsepower motor used to reduce eight inch thick copper slabs down to 1/2 inch thickness. It draws 4680 amps maximum at 700 volts. It clearly dwarfs the technician standing nearby.

    clipboard_e84eeecdd7e6c42fa1a5efcfa70de1596.png

    Figure 1.1.4 : An industrial DC motor

    Now that we have a little background and perspective, it's time to look at mathematics, specifically, how we represent and manipulate values that may be very, very large or very, very small, all while keeping appropriate accuracy.


    This page titled 1.1: Introduction is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by James M. Fiore via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.