Physics
DC Circuit
A DC circuit is an electrical circuit where direct current (DC) flows in one direction. It typically consists of a power source, such as a battery, and various components like resistors, capacitors, and inductors. In a DC circuit, the voltage remains constant over time, making it different from an AC circuit where the voltage alternates.
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12 Key excerpts on "DC Circuit"
eBook - PDFElectronics
Fundamentals for the Water and Wastewater Maintenance Operator
- Frank R. Spellman, Joanne Drinan(Authors)
- 2000(Publication Date)
- CRC Press(Publisher)
Direct Current (D-C) Review TOPICS Current Flow Potential Difference (Voltage) Resistance Ohm's Law Series and Parallel Resistive Circuits Electric Power E-I Graph Kirchhoff's Laws Voltage and Current Dividers Switches Capacitors 3.1 INTRODUCTION Just as the foundation of a new house is usually constructed before the rest of the house is built upon it, the basics of electricity must be stud-ied first before attempting to study electronics. This chapter is a review on those basic aspects of d-c (direct current) that apply to electronics. By no means does it cover the whole d-c theory (for more in depth coverage of d-c, we recommend the first volume of this series: Electricity), but merely those topics that are essential to basic electronics. CURRENT FLOW Electron movement, or flow, in a conductor is called electric current. To produce current, the electrons must be moved by a potential difference (or voltage). The flow of water is usually measured as the number of Direct Current (D-C) Review 25 3 Direct Current (D-C) Review 3.2 Key Terms Used in This Chapter AMPERE The basic unit of electrical current. CAPACITOR CIRCUIT CONDUCTANCE CONDUCTOR DIRECT CURRENT (D-C) ELECTRON FUSE KIRCHHOFF'S LAWS LOAD OHM'S LAW POTENTIAL Two electrodes or sets of electrodes in the form of plates, separated from each other by an insulating material called the dielectric. The complete path of an electric current. The ability of a material to conduct or carry an electric current. It is the reci-procal of the resistance of the material and is expressed in mhos. Any material suitable for carrying electric current. An electric current that flows in one direction only. A negatively charged particle of matter. A protective device inserted in series with a circuit. It contains a metal that will melt or break when current is increased beyond a specific value for a definite period of time.
eBook - PDF- Michael Tammaro(Author)
- 2019(Publication Date)
- Wiley(Publisher)
An electric circuit is a conducting path along which charges flow, driven by differences in electric potential. The late 1800s saw the first widespread use of electric circuits with the advent of electric lighting. Since then, electric circuits have had an integral role in almost every technological development. The miniaturization of electric circuits and devices has led to tremendous breakthroughs in computers and communications. This photograph shows part of a silicon computer chip, which itself is a complex electrical circuit. The gold wires connect the chip to pins that allow it to be plugged into a circuit board. (The image here is a scanning electron micrograph at 90× magnification.) Eye of Science/Science Source/Photo Researchers** Direct Current Circuits 20 538 Electric Current and Electromotive Force | 539 20.1 Solve problems dealing with the basic definition of electric current. The movement of electric charges from place to place plays a fundamental role in almost every technology and convenience of modern life. The basic quantity that defines the movement of charges through conductors is called electric current, or simply current. A closed path of conducting material along which current flows is called an electric circuit. Here in Chapter 20 we explore electric circuits, restricting ourselves to direct current (DC) circuits—that is, those in which the current at a particular point is always in the same direction. Electric Current There are a wide variety of materials that conduct electricity. The charge carriers in liquid solutions or gases may be positive or negative ions. Electrons are the charge carriers in metals. The movement of electrons through a metal is pictured schematically in Animated Figure 20.1.1. In this two-dimensional view, the large circles represent the metal atoms, which are arranged in a regular array, called a lattice.
eBook - ePubLearn Audio Electronics with Arduino
Practical Audio Circuits with Arduino Control
- Charlie Cullen(Author)
- 2020(Publication Date)
- Focal Press(Publisher)
Chapter 3 DC Circuits In this chapter, we will learn how to analyse direct current (DC) circuits. The basic principle behind DC Circuits is that they are time-invariant – they do not change. This means we can specify voltage and current values and assume that these will remain the same as long as the power supply to the circuit is connected, which differs from the alternating current (AC) circuits we will encounter later in the book. This chapter represents our first real introduction to electronic circuit analysis, where we will learn the basic equations and rules of series and parallel circuits. You may find the maths in the chapter examples takes a little time to work through (particularly for parallel circuits) but remember that the equations themselves are quite straightforward – it’s the scales and symbols that take some time to get used to. We will begin by learning about Ohm’s Law, a fundamental equation that defines the relationship between voltage, current and resistance in a circuit. Ohm’s Law was briefly introduced in chapter 1 as an example of a relatively straightforward equation used in electronics, and now we will learn how to work with it in practical terms. We will also encounter two other fundamental aspects of DC Circuit analysis – Kirchoff’s Voltage Law (KVL) and Kirchoff’s Current Law (KCL). These two laws are used in all electronic circuits, so this chapter will spend a little time deriving them and explaining their use
- Miguel F. Acevedo(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
3 Fundamentals of Direct Current Electric CircuitsThis chapter is one of several providing a very basic review of those major concepts of electrical circuits that we need in order to understand electrical power systems. In this chapter, we review basic electrical quantities and circuits, introducing Ohm’s law and the fundamentals of circuit analysis methods including Kirchhoff’s voltage and current laws, nodal and mesh analysis, and Thévenin and Norton theorems. In preparation for understanding power transfer, we cover modeling of voltage and current sources and the basics of maximum power transfer. In this chapter, we will focus on direct current (DC) circuits, and later, in Chapter 5 , we introduce alternating current (AC) circuits. This topic is expanded in Chapter 8 discussing AC circuit analysis and power calculation for AC circuits, and in Chapter 10 when we introduce transformers and three-phase circuits. Basic DC Circuit analysis is covered in many textbooks used in introductory circuit analysis courses and can serve as supplementary material [1–3 ]. Reviews are also available in textbooks devoted to renewable energy [4 ,5 ].3.1 Basics of Electric Circuits3.1.1 Principles of Electrical QuantitiesElectrical charge is a fundamental property of matter that can both generate and interact with electromagnetic fields. Charge can be positive or negative; at the subatomic level, protons represent positive charge, whereas electrons have negative charge. The unit of charge is the coulomb or C, where 1 C is the equivalent charge of 6.2 × 1018 electrons. In a conductor, free electrons can flow and represent a movement of negative charge.Voltage is the potential energy difference between two points in an electric field, measured per unit charge. Being potential energy means it is available to perform the work of moving a unit charge against an electric field. Intuitively, voltage is the energy available to cause electrons to flow through a conductor. Its unit is volt or V, which is defined as joule/coulomb (J/C), and is named volt in honor of Alessandro Volta. In general, work and charge vary with time. Denoting charge by q , voltage by v , and work by w
eBook - PDF- Charles A. Gross, Thaddeus A. Roppel(Authors)
- 2012(Publication Date)
- CRC Press(Publisher)
41 Electrical Circuit Concepts 2.4 The dc Mode The term “dc” historically means “direct current,” but it means “time invari-ant” in contemporary usage . A “DC Circuit” is a circuit operating in the dc mode . Observe that, for dc: v L di dt i C dv dt = ⋅ = = ⋅ = 0 0 This means that inductors and capacitors become shorts, and opens, respectively, and hence are trivialized . When a general circuit is redrawn for dc operation, the L ’s and C ’s “disappear,” the “ L ’s” are replaced by shorts, and the “ C ’s” are replaced by opens! Thus, the basic set of ideal circuit elements is reduced from five ( v -source, i -source, R , L , and C ) to three ( v -source, i -source, and R ) for the DC Circuit . There is a conventional notation that is commonly used in electrical engineering, and one which we will use as well (except when otherwise noted) . v i v t i t or or instantaneous voltage or c = = ( ) ( ) urrent or constant (dc) voltage or current V I = For the DC Circuit, the v , i relation for the resistor is Ohm’s law ( Ω L) . Example 2.5 Consider the circuit of Figure 2 .6a, for which v ( t ) = 100 V for − ∞ ≤ t ≤ + ∞ , putting the circuit in the dc mode . Draw the corresponding DC Circuit, replacing L ’s with shorts and C ’s with opens . Solution: See Figure 2 .6b and 2 .6c . Note the alternate symbol for a dc voltage source . Also note that nodes d , e , and f are eliminated ( d merges with c , e is trivial since it terminates in an open, and f merges with o ) . Fundamentals of Electrical Engineering 42 THE SERIES CONNECTION There are usually some simplifications that one can make in a given circuit which will simplify its analysis . One such simplification is series reduc-tion . Consider “ n ” resistors connected as shown in Figure 2 .7a, such that the same current flows through each .
eBook - PDFElectricity
Fundamentals for the Water and Wastewater Maintenance Operator
- Frank R. Spellman, Joanne Drinan(Authors)
- 2000(Publication Date)
- CRC Press(Publisher)
TOPICS The Simple Electric Circuit Ohm's Law Electric Power Electric Energy Series D-C Circuit Characteristics Parallel D-C Circuits Series-Parallel Circuits INTRODUCTION In Chapters 1 and 2, we introduced some of the basic concepts of electricity. Now we will use those fundamental ideas along with the con- cepts contained in Ohm's Law to begin to understand the direct current (d-c) electric circuit. THE SIMPLE ELECTRIC CIRCUIT An electric circuit includes an energy source [source of electromo- tive force (ernf) or voltage; that is, a battery or generator], a conductor (wire), a load, and a means of control (see Figure 3.1). The energy source could be a battery, as in Figure 3.1, or some other means of producing a voltage. The load that dissipates the energy could be a lamp, a resistor, or some other device (or devices) that does useful work, such as an electric toaster, a power drill, radio, or soldering iron. Conductors are wires that offer low resistance to current (see Chapter 4); they connect all the loads in the circuit to the voltage source. No electrical device dissipates energy unless current flows through it. Because conductors, or wires, are not per- fect conductors, they heat up (dissipate energy), so they are actually part of the load. For simplicity, however, we usually think of the connecting D-C ~ircuits 41 wiring as having no resistance, because it would be tedious to assign a very low resistance value to the wires every time we wanted to solve a problem. Control devices might be switches, variable resistors, circuit breakers, fuses, or relays. A complete pathway for current flow, or closed circuit (Figure 3.1), is an unbroken path for current from the emf, through a load, and back to the source. A circuit is called open (see Figure 3.2) if a break in the cir- cuit (e.g., open switch) does not provide a complete path for current. 42 DC Circuits
eBook - PDF- David Halliday, Robert Resnick, Kenneth S. Krane(Authors)
- 2019(Publication Date)
- Wiley(Publisher)
When currents are flowing in the wires, the conclu- sions of electrostatics are no longer valid; in particular, we know from our discussion in Section 29-4 (see Eq. 29-12) that when a current i flows in a conductor there is a potential difference V iR across the conductor. However, the DC CircuitS I n Chapter 29 we discussed some general properties of current and resistance. In this chapter we begin to study the behavior of specific electric circuits that in- clude resistive elements, which may be individual resistors or the internal resistances of circuit elements such as batteries or wires. We confine our study in this chapter to direct current (DC) circuits, in which the direction of the current does not change with time. In DC Circuits that contain only batteries and resistors, the magnitude of the current does not vary with time, whereas in DC Circuits containing capacitors, the magnitude of the current may be time dependent. Alternating current (AC) circuits, in which the current changes direction periodi- cally, are considered in Chapter 37. CHAPTER 31 CHAPTER 31 Figure 31-1. A battery is connected to an electrical device by two wires. The direction of the current is opposite to the direc- tion of motion of the electrons. – + Current Wire Wire Battery Electrons Device resistance of the wires is usually very small compared with the resistance of the device in our circuit, so we are usually justified in neglecting the effect of the wires; in particular, we assume that there is no potential drop in the wires, and in this case the full voltage difference of the battery terminals does appear across the terminals of the device. The battery can be considered a “pump” for charge, as if it were bringing positive charge through the battery from the negative terminal to the positive one. In actuality, it is usually the motion of the negatively charged electrons that is responsible for the current flow.
eBook - PDFPhysics of Electronic Materials
Principles and Applications
- Jørgen Rammer(Author)
- 2017(Publication Date)
- Cambridge University Press(Publisher)
5 Electric Circuit Theory Electronics is about pushing electrons around inside matter in a controlled manner, creating flows of electric charge in circuits. This should be done to provide calculated voltages over components, thereby providing the right current flows, ensuring the right voltage drops over other components, etc. Designing the functioning of electronic circuits can be done without understanding the physics of the components. All that is needed is knowledge of the components’ current–voltage relationships, their I – V characteristics: what is the cur-rent response through a component to an electric potential difference, or voltage, between its terminals, or vice versa, what is the needed current through a device to provide a certain voltage across its terminals. The art and craft of electronics then emerges from understand-ing electronic circuitry as represented by symbolic circuit diagrams. The main intention of this book is to provide the physical understanding of the I – V characteristics of electronic components, the physics of electronics, but electric circuits are discussed throughout the chapters, here basic circuit theory. 5.1 Wires and Currents An electric circuit consists of electronic components connected by wires , thin filaments of good conducting material such as a clean metal. The resistance of a wire is assumed so small in comparison with the resistance of other components that the wires can be assumed perfect conductors, i.e. having zero resistivity or infinite conductivity. Inside a perfect con-ductor, the electric field vanishes, since the slightest field would create an infinite current, i.e. instantaneously nullifying it. The electric potential is thus the same in a wire, and no charge inhomogeneity exists in wires. In a wire an electric current thus flows without the presence of a voltage difference; the charged electrons flow like an incompressible liquid.
eBook - PDF- SA Chuturgoon(Author)
- 2021(Publication Date)
- Troupant(Publisher)
41 Direct current (DC) circuit theory TVET FIRST 4 Module Overview of Module 4 Energy cannot be created or destroyed, but it can be converted from one form into another. Direct current (DC) electrical energy is stored in batteries in the form of chemical energy and converted into electrical energy when needed. In this module we are going to learn how to solve electric circuits supplied from a DC source. When you have completed this module, you should be able to: Unit 4.1: Basic electricity, Ohm’s law and Joule’s law ● State what is meant by: { Current. { Potential difference (voltage). { Resistance. ● State Ohm’s law. ● State Joule’s law. ● Use Joule’s law to determine the heat energy dissipated in electrical circuits. ● Calculate the cost of electrical energy (kW × hours × tariff). Unit 4.2: Methods of connecting resistors in a circuit ● Use Ohm’s law to determine current, voltage, resistance, volt drop and power in a circuit having resistance connected in series, parallel and series-parallel (maximum four resistors). Unit 4.3: Factors influencing the resistance of a conductor ● State the factors that affect the resistance of a conductor. ● State what is meant by resistivity. ● Calculate the resistance of a conductor at constant temperature. ● Define temperature coefficient of resistance. ● State how temperature affects the resistance of pure metals, alloys, carbon, electrolytes and insulators. ● Explain the difference between positive and negative temperature coefficients. ● Calculate the resistance of a conductor at any temperature with the initial resistance given at zero degrees Celsius. Unit 4.4: Cells and batteries ● State the function of a cell or battery. ● Differentiate between primary and secondary cells. ● Explain with the aid of a circuit the difference between emf and potential difference.
eBook - PDF- Tommy Ferreira, Trevor Adams, Tommy Ferreira, Trevor Adams(Authors)
- 2021(Publication Date)
- Future Managers(Publisher)
Without a good understanding of these basic concepts, definitions and laws, you will find it difficult to understand electrical trade theory or any other electrical subject. 4.1 Ohm’s law 4.1.1 Terminology Current Current refers to a flow of electrically charged particles past a certain point in a circuit in a given time. The particles can be negatively charged electrons (electron flow) or positively charged protons (conventional current flow), as seen in Figure 4.1. The common symbol for current is the uppercase letter ‘I’. The standard unit of measurement is the ampere (commonly referred to as ‘amps’), and the symbol used is a capital ‘A’. D i r e c t i o n o f c u r r e n t D ir e c t i o n o f c u r r e n t F l o w o f e l e c t r o n s F l o w o f e lectr o n s Figure 4.1: Circuit showing current flow and electron flow Potential difference (voltage) Just as a difference in water pressure must exist for water to flow between two points, a difference in electrical pressure must be present to cause electrical current to flow. The greater the pressure, the greater the flow will be in both cases. The difference in electrical pressure between two points is termed ‘potential difference’. The unit of measurement for voltage is volt, and the symbol used to represent volt is a capital ‘V’. Definition Volt – the unit of measurement of force used to produce an electric current 35 N1 Electrical Trade Theory Resistance Resistance is the opposition to the free flow of electrons within a circuit. The device or wire designed specifically to oppose the flow of current in a circuit is known as a resistor. If it is designed so that its value can be adjusted, it is known as a variable resistor or a rheostat. A variable resistor is made to be readily adjustable. A preset resistor is one that is set to a certain critical value by the manufacturer of a product.
eBook - PDFElectronic Systems
Study Topics in Physics Book 8
- William Bolton(Author)
- 2013(Publication Date)
- Butterworth-Heinemann(Publisher)
Teaching note Experiments appropriate to this chapter may be found in Nuffield Advanced Physics: Teachers' Guide 6. 22 Direc t-curren t circu its 23 Direct-current circuits A current / through a resistor of resistance R occurs when there is potential difference V across it, V = IR Units: R - Ω, / - A, V-V. (Book 4: Basic Electricity and Magnetism , chapter 1, considers this relationship in more detail.) When we have a network of resistors and different branches in a circuit along which the current can flow then measurements with an ammeter show that the sum of the currents entering any junction is equal to the sum of the currents leaving that junction. Thus, for the junction point in Figure 2.1 we have Λ + / 2 A +U +h This statement is known as one of Kirchoff's laws. The law is a conse-quence of the conservation of charge since, as charge does not accumulate at the junction, the amount of charge that arrives at the junction in a certain time must be equal to the amount leaving it in the same time. Figure 2.2 shows a simple circuit containing a battery and a resistor. The battery has an internal resistance R x and an e.m.f./s'. Measurements show (see Book 4: Basic Electricity and Magnetism , chapter 1, for an introductory consideration of this topic) that the e.m.f. is equal to the potential drop across the internal resistance R x and the resistor R. Figure 2.2 E.m.f. E | R E = R { I + RI The e.m.f. is, however, the energy per unit charge utilised in the current through both the internal resistance and the external circuit resistance. The RI product and the R^I product represent the potential differences across those resistances. Potential difference is, however, the energy dissipated per unit charge. Thus the equation above represents a state-ment of the conservation of energy for the circuit. The energy per unit charge supplied by the battery equals the energy dissipated per unit charge in the resistances.
eBook - PDF- John Matolyak, Ajawad Haija(Authors)
- 2013(Publication Date)
- CRC Press(Publisher)
275 © 2010 Taylor & Francis Group, LLC Direct Current Circuits 15.1 INTRODUCTION Electric circuits are an excellent example of employing the properties of electric charges, covered in Chapters 13 and 14, for practical purposes. Circuits generally consist of (1) a source of charge, for example, a battery or an electric generator, (2) a conducting path for charge and hence energy flow, (3) a “load,” that is, a charge/energy consuming device such as a radio, light bulb, and electric motor. 15.1.1 C ELLS AND B ATTERIES AS A S OURCE OF C HARGE A simple chemical cell can be constructed by placing two dissimilar metals, say A and B, in a dilute acid. As an example, the metals (electrodes), generally in the shape of rods, could be copper and zinc. Most metals dissociate (dissolve) slightly in the acid. The dissociation results in a positive ion being removed from the metal and entering the acid solution. That metal ion leaves behind at least one electron and therefore negatively charges the rod from which it came. Over time, as the process continues, the rod becomes negative enough to attract some of the positive ions in solution back to it. Eventually, an equilibrium is reached so that the number of positive ions leaving the rod equals the number attracted back to it. The electrode now is negatively charged, so a potential difference exists between it and the solution, which is at a higher potential. A similar process occurs with rod B and it likewise reaches an ion dissociation–attraction equilibrium. But metal B is dissimilar to electrode A and suppose it is more electronegative, that is, retains more electrons per dissociation than A. Both A and B are negative, so they are at a lower potential than the solution, but because of its greater electron retention, B is at a lower potential than A. This potential difference is tradition-ally called the electromotive force (a misnomer) or emf of the cell.
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