This test will assess your knowledge of and ability to apply the principles of basic electronics. The handbook includes information on alternating current ac and direct current dc theory, circuits, motors, and generators. Both ac and dc describe types of current flow in a circuit. As it will be shown later, alternators operate with both alternating ac and directcurrent dc electric power. Network theory response of ac circuits in the previous chapter, we discussed the transient response and steady state response of dc circuit. Designed for new electronics learners who have little to no knowledge of the field. In this section a pool of electrical topics ranging from atomic structure, ohms law to ac machines are covered. Dc is current that flows in one direction with a constant voltage polarity while ac is current that changes direction periodically along with its voltage polarity. Ac circuit calculations for resistive circuits are the same as for dc.
While direct current has one form of power, alternating current has three different forms of power that are related in a. Written with the student electrician in mind, dc theory, 3e uses a readerfriendly approach and begins with the basics of electricity and dc circuits, including how properties of materials are categorized within conductors, semiconductors, and insulators. Ac and dc current this is the third characteristic of electricity. For the smallsignal model to apply, the transistor must stay in the active saturation region for the entire range of input signals. Overview the acdc motor theory course was specifically developed for electricians and electronic technicians as well as for the multicraft training needs of process and manufacturing facilities. To explain the details of why this is so, a bit of background knowledge about ac. Thomas edison and alessandro volta were pioneers in dc.
Basic acdc circuit theory, analysis and problems photo credit. Therefore ac is prevented from flowing or is choked off while dc is allowed to pass. An essential part of an acdc power supply circuit is the. Ac vs dc alternating current vs direct current difference.
Ac motors are different from dc or direct current motors in their use of alternating current, which changes direction. In direct current dc, the electric charge current only flows in one direction. Understand the electrical principles of direct cur rent dc. The input to a dc dc converter is an unregulated dc voltage vg. Brush up on some basic electrical theory and deepen your knowledge about electricity.
Volume 3 of 4 module 7 basic ac theory this module describes the basic concepts of alternating current ac electrical circuits and discusses the associated terminology. Most students of electricity begin their study with what is known as direct current dc, which is electricity flowing in a constant direction, andor possessing a voltage with constant polarity. Whats the difference between alternating current and direct current. This test is comprised of 90 questions in the following areas.
Finding motor hp horse power, kva kilovolt ampere kw input, when motor hp is known kw kilowatts amperes, when kva is known. For this reason, the ac generator will be discussed first. This effect is used in power supply circuits where the public ac mains line supply has to be converted to a dc supply suitable for powering electronic circuits. The dc can be considered a particular case of the general ac, with frequency equal to zero. The frequency of an alternated circuit is measured by the number of times the. Ohms law is designed for new electronics learners who have little to no knowledge of the field. The handbook includes information on alternating current ac and direct current dc theory, circuits, motors, and. The approach adopted is that of starting with the basic laws of dc electricity and expanding. Ac motors do not require the brushes power contacts or commutators that dc motors need. While direct current has one form of power, alternating current has three different forms of power that are related in a unique relationship. Ac motors transform electrical energy to mechanical energy. These ac motors revolutionized industries and paved the way for uses in. When ac theory is introduced, and especially when there is a bias towards radio frequencies, the very first new idea required by many people at least is a correct understanding of the word electricity. In 1886, ganz works, an electric company located in budapest, electrified all of rome with ac.
Objective identify the components of an ac motor and explain their function. Electrical science module 2 basic dc theory ntc sites. You can also go to print custom pages to select the part of the pdf that you want. Its operation is based on the principle that when a current carrying conductor is placed in a. Network theory response of ac circuits tutorialspoint. Pdf dc motor dc motor theory cahtayu cahtayu academia. This exam will test you level of comprehension on the basic ac theory section of the electrical training course.
Ohms law will help viewers to write ohms law in three different forms as well as cover. Understand the requirements and configurations of electrical circuits. Dc dc power converters are employed in a variety of applications, including power supplies for personal computers, office equipment, spacecraft power systems, laptop computers, and telecommunications equipment, as well as dc motor drives. Electric charge in alternating current ac, on the other hand, changes direction. Ac motors are still heavily used in modern life, and you may find them in appliances and gadgets in your own home.
In particular, if a coil rotates in the presence of a magnetic field, the induced emf varies sinusoidally with time and leads to an alternating current ac, and provides a source of ac. Ac waveform and ac circuit theory ac sinusoidal waveforms are created by rotating a coil within a magnetic field and alternating voltages and currents form the basis of ac theory direct current or d. Circuit theory i superposition the superposition principle states that the voltage across or current through an element in a linear circuit is the algebraic sum of the voltages across or currents through that element due to each independent source acting alone. This type of voltage is called alternating current ac voltage. This course consists of 11 interactive, online lessons that address ac and dc motor theory. Direct current also known as dc is the flow of charged particles in one unchanging direction most commonly found as electron flow through conductive materials. Ac circuits dc circuits discrete components digital. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Alternating current vs direct current ac vs dc ac and dc differ in several ways from generation to transmission, and distribution, but for the sake of simplicity, we will keep the comparison to their characteristics for this post. Dc motor principle a machine that converts dc power into mechanical energy is known as dc motor. Basic ac theory i i direct current dc alternating current ac i i figure 1. Pdf file contains bookmarks, thumbnails, and hyperlinks to help you navigate through the document.
Where did the australian rock band ac dc get their name from. A constant voltage source is called a dc voltage with a voltage that varies periodically with time is called an ac voltage. Module 6 dc motors this module describes the types of dc motors and includes discussions of speed control, applications, and load characteristics. Acdc power supplies xp power offers the worlds strongest range of ac to dc power supplies, with products ranging from 3 watts to over 5000 watts. The simplest elementary generator that can be built is an ac generator. Dc can be found in just about every home and electronic device, as it is more practical compared to ac from power stations for many consumer devices. When ac theory is introduced, and especially when there is a bias towards radio frequencies, the. Series resistances still add, parallel resistances still. The teaching of basic science often involves what are known as lies to children, and. The difference between ac and dc lies in the direction in. Read about simple ac circuit calculations basic ac theory in our free electronics textbook network sites. Dc circuits is an electrical training video that will help viewers to understand kirchhoffs law as well as cover superposition, thevenins, and nortons theorem. Basic electrical theory overview of ac motors, transformers and measuring instruments instructor. Most students of electricity begin their study with what is known as direct current.
There are two types of current, direct current dc and alternating current ac. Electrical theory electrician exams practice tests. We can find the following quantities by using below formulas chart electrical formulas in dc full load current in amperes alternating current ac motors alternating current ac single. An understanding of how an ac generator develops an ac output will help the student analyze the ac power generation process. Ac circuits dc circuits discrete components digital circuits general example question. How to select the proper equation to calculate current, voltage, or resistance. In this post we cover ohms law, ac and dc current, circuits and more. If the flow of electron does not change his path and is in unidirectional flows or movements inside a circuit it is called as dc or direct current. Ac motors are widely used to drive machinery for a wide variety of applications.
In the analysis of an ac circuit, voltage and current phasors are used with resistances and reactances in much the same way that voltages and currents are used with resistances in the analysis of a dc circuit. The major difference between the ac and dc, which is also the cause of their different characteristics, is the. Dc to ac converters converts dc to ac power by switching the dc input voltage or current in a predetermined sequence so as to generate ac voltage or current output. Many of our power supplies are classed as the worlds smallest and are designed with a focus on low noise, high efficiency and reliability.
Understand the electrical principles of alternating current ac. Electricity or current is nothing but the movement of electrons through a conductor, like a wire. Generate the dc voltages needed for most electronics starting with the ac power that comes through the power line 120 v rms 9df 9sin 7 w f 60 hz t 16. A dc motor is an electrical machine that converts electrical energy into mechanical energy the working of dc motor is based on the principle that when a current carrying conductor is placed in a magnetic field, it experiences a mechanical force. Jan 27, 2010 this feature is not available right now. Finding motor hp horse power, kva kilovolt ampere kw input, when motor hp is known kw kilowatts amperes, when kva is. The purpose of a rectifier circuit is to convert ac power to dc.
Direct vs alternating current distribution systemsthat are far more ef. With this method, voltage forces electrons to flow first in one direction, then in the opposite direction, alternating very quickly. But inorder to understand the work in depth knowledge in electrical basics is required. Understand the requirements of electrical circuit computations. Looking over his notes from ac theory, the student proceeds to build this power supply circuit complete with a lowpass. Dcdc power converters are employed in a variety of applications, including power supplies for personal computers, office equipment, spacecraft power systems, laptop computers, and telecommunications equipment, as well as dc motor drives.
Coverage gradually progresses to tackle more complex topics, like dc parallel circuits, dc. Dc motors although ac motors are used in most of the cases, dc motors have many applications and used for multipurpose applications. Most students of electricity begin their study with what is known as direct current dc, which is electricity flowing in a. Learn about ac circuit theory, what is alternating current ac, how it works, basic ac source and ac generators, difference between ac and dc and how transformers are used in ac circuits. With this method, the voltage forces the electrons to flow. Ac induction motor speed control so what can we do to control the speed of an ac induction motor. Electrical fundamentals introduction to direct current dc theory. Ohms law will help viewers to write ohms law in three different forms as well as cover how to select the proper equation to calculate current, voltage, or resistance. The input to a dcdc converter is an unregulated dc voltage vg.
Solve for unknown quantities of resistance, current, and voltage in a parallel circuit. Electrical basic theory is tested in almost all the license exams for understanding the ability of the electrical knowledge of the candidate. Why, alternating current and direct current, of course. To understand how these motors operate, a knowledge of the basic theory of operation of ac motors is necessary. Thomas edison, on the other hand, had constructed 121 dc power stations in the united states by 1887. As you study this and the following modules on ac alternating current theory, notice that the circuits described use two main components, inductors and capacitors, which in many ways seem to have.
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