Physics
Voltage Source
A voltage source is a device that provides a constant electric potential difference, or voltage, between its terminals. It is commonly used in electrical circuits to supply a consistent voltage to power various components. Voltage sources can be either direct current (DC) or alternating current (AC) and are essential for the operation of many electrical devices.
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5 Key excerpts on "Voltage Source"
- Dennis L. Eggleston(Author)
- 2011(Publication Date)
- Cambridge University Press(Publisher)
1 Basic concepts and resistor circuits 1.1 Basics We start our study of electronics with definitions and the basic laws that apply to all circuits. This is followed by an introduction to our first circuit element – the resistor. In electronics, we are interested in keeping track of two basic quantities: the currents and voltages in a circuit. If you can make these quantities behave like you want, you have succeeded. Current measures the flow of charge past a point in the circuit. The units of current are thus coulombs per second or amperes , abbreviated as A. In this text we will use the symbol I or i for current. As charges move in circuits, they undergo collisions with atoms and lose some of their energy. It thus takes some work to move charges around a circuit. The work per unit charge required to move some charge between two points is called the voltage between those points. (In physics, this work per unit charge is equivalent to the difference in electrostatic potential between the two points, so the term potential difference is sometimes used for voltage.) The units of voltage are thus joules per coulomb or volts , abbreviated V. In this text we will use the symbol V or v for voltage. In a circuit, there are sources and sinks of energy. Some sources of energy (or voltage) include batteries (which convert chemical energy to electrical energy), gen-erators (mechanical to electrical energy), solar cells (radiant to electrical energy), and power supplies and signal generators (electrical to electrical energy). All other electrical components are sinks of energy. Let’s see how this works. The simplest circuit will involve one Voltage Source and one sink, with connecting wires as shown in Fig. 1.1 . By convention, we denote the two sides of the Voltage Source as + and − . A positive charge moving from the − side to the + side of the source gains energy. Thus we say that the voltage across the source is positive.
eBook - PDF- SA Chuturgoon(Author)
- 2021(Publication Date)
- Troupant(Publisher)
Simply put, potential difference is an electrical pressure that produces current flow in a closed electric circuit . It is also known as terminal voltage . Potential difference is represented by the symbol V or PD and is measured in joules per coulomb or volts. elementary charge: charge carried by a single electron electricity (current flow): flow of charge (electrons) in a specific direction conventional current flow: flow of current from the positive terminal of a battery to the negative terminal of the battery electron flow: the flow of current from the negative terminal of a battery to the positive terminal of the battery circuit: a movement that starts and finishes at the same point closed electric circuit: a complete electrical connection around which current flows terminal voltage: potential difference between the terminals of a cell when current flows 44 Module 4 TVET FIRST 4.1.3 Electromotive force Electromotive force is an electrical potential produced by any source of electrical energy. Its function is to initiate and maintain a potential difference. Electromotive force (emf) is represented by the symbol E and is also measured in volts (V). Definition of electromotive force (emf) Electromotive force is the voltage measured across the ends of an energy source of an open circuit . (Remember that no current is flowing in an open circuit.) Sources of electromotive force The following are sources of electromotive force or sources of electrical energy: • Cells or batteries. • Generators . • Solar energy . • Heat. • Friction . Electromotive force versus potential difference Did you notice that potential difference and electromotive force are both measured in volts? Over the years people have started to refer to both potential difference and electromotive force as voltage (which also means electrical potential). So, let us talk about the differences between the two in order to avoid confusion.
eBook - PDF- A. Henderson(Author)
- 2014(Publication Date)
- Arnold(Publisher)
In that case, however, the source currents cannot be calculated. Two current sources in series are forbidden if the sum of the source strengths is not zero (for in this case KirchhofF s current law for the node between the two sources) is not valid. Two current sources in series are not forbidden if the sum of the source strengths is zero. In that case the source voltages cannot be calculated. In network theory it often happens that there is analogy between two formulas, between two elements or between two circuits. For instance, one Kirchhoff's law turns into the other if one substitutes voltage for current and vice versa. We therefore say that the current law is the dual of the voltage law and vice versa. The dual character is also found in • voltage - current • open nodes - short circuit • resistance - conductance In the following chapters we shall often meet this phenomenon of duality. 1.3 Energy and power The voltage V A B between two points A and B is defined as the work needed to move a unit charge (1 C concentrated in a point) from point B to point A. If the charge is Aq the work is therefore AW = (V A - V B )Aq = V AB Aq, (1.14) in which VA and VB are the potentials of the points A and B. If VAB is constant (d.c.) and if the work is done in a time At, the average power is p _ A W _ Aq r At v At ' in which V = VAB-For At -> 0 we obtain P = VI. (1.15) So the power, in the case of d.c, is the product of voltage and current. Energy is expressed in joule (J), power in watt (W). Power can be consumed or supplied. If a current I flows through a network N with two terminals (also called a one-port) and if the polarity of the voltage V is such that I flows from + to - the power consumed is positive (Figure 1.11). 18 d.c. currents and d.c. voltages The Voltage Source transports (positive) charge from minus to plus and so delivers electrical energy to N (this energy is supplied by the chemical or mechanical system outside the network).
eBook - ePub- Stephen Sangwine(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
Power sources and power supplies 4 ObjectivesTo introduce the main sources of electrical energy used in electronic systems, including mains supplies, batteries, and photovoltaic cells.To introduce the concept of a power supply.To discuss the characterization and performance of power supplies.To explain the functions of the main subcircuits found in a power supply.To explain the operation of linear and switching voltage regulators.All electronic circuits and systems require energy to operate. Energy is required to move electric charge; to produce heat, light, or sound; to produce mechanical movement; and to manipulate information (as in a computer). Energy is a conserved physical quantity: in a closed system energy can be neither created nor destroyed, although it can be converted from one form to another. In electronic engineering, we are usually concerned with electrical energy, although other forms of energy are also important. Heat, for example, is produced in electronic circuits, usually as a by-product of a useful function, and is discussed in Chapter 7 . Energy may be stored as chemical energy in a cell or battery. Chemical energy sources are discussed later in this chapter.Energy is the capacity to do work. The International System of Units (SI) unit of energy is the joule (J).While the importance of energy should not be forgotten, electronic engineers more frequently use the concept of power. Power can be used to quantify the rate at which heat is produced in a resistor, the mechanical output of a motor, or the rate at which an electronic system takes energy from its energy source.Power is the rate of conversion, utilization, or transport of energy. The SI unit of power is the watt (W), which is 1 J s−1 .The terms a.c. and d.c. stand for alternating current and direct current respectively. We customarily talk about a.c. voltage and d.c. voltage, even though technically this is nonsense — what is an “alternating- current voltage?” We can avoid the term d.c
eBook - PDFTHE LTSPICE XVII SIMULATOR
Commands and Applications
- Gilles Brocard(Author)
- 2021(Publication Date)
- Adolf Würth GmbH & Co. KG(Publisher)
Figure 17.1 523 17 Voltage and current source editor 17 .3 All simulations need an independent source 17 .3 All simulations need an independent source The configuration of a voltage or current source must be adapted to the simulation chosen . To be able to simulate a circuit, you must always add a source which calls the system and whose parameters correspond to the simulation chosen. DC op pnt For simulation of an operating point , at least one independent DC source is required, which is generally also the power supply for the system. Parameters: DC voltage or current. DC transfer For a transfer function simulation around an operating point, an independent DC source is required, which is also often the power supply for the system. Parameters: DC voltage or current. DC sweep For an automatic simulation of several points of constant bias, you need one to three independent DC sources which are either power sources or secondary bias sources. Parameters: DC voltage or current. AC analysis For a frequency simulation in the linear domain , an independent source configured as an AC signal is required. This will be the excitation source of the system, similar to a low-frequency, arbitrary or high-frequency generator for an assembly on the bench. Parameters: AC voltage or current (right part of the source editor). Noise For a noise frequency simulation in the linear domain , an independent AC source is required, which is the excitation source of the system, similar to a low-frequency, arbitrary or high-frequency generator for an assembly on the bench. Parameters: AC voltage or current + the source impedance which influences the noise level (right part of the source editor).
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