Physics
Voltage
Voltage is a measure of the electric potential difference between two points in a circuit. It is the driving force that pushes electric charges through a conductor. Voltage is measured in volts and is essential for the flow of current in an electrical circuit.
Written by Perlego with AI-assistance
Related key terms
1 of 5
10 Key excerpts on "Voltage"
eBook - PDFElectrotechnics N4 Student's Book
TVET FIRST
- SA Chuturgoon(Author)
- 2021(Publication Date)
- Troupant(Publisher)
1.1.2 Potential difference Definition of potential difference The potential difference between two points in a circuit is the work done when 1 C of charge is moved from one point to another. Simply put, potential difference is an electrical pressure that produces current flow in a closed electric circuit . It is also known as terminal Voltage . electricity (current flow): flow of charge (electrons) in a specific direction electron: negative charge carrier orbital: the path followed by an electron around the nucleus of an atom nucleus: the centre of an atom, which is made up of protons and neutrons proton: positive charge carrier neutron: particle with no electrical charge atom: the smallest particle of an element valence electron: electron in the outermost orbital of an atom excited (electron): in an energy state higher than its normal or ground state elementary charge: charge carried by a single electron 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 Starter activity Discuss the following in class: ● In our previous encounters with electricity related subjects, we came across terminology such as terminal Voltage, electromotive force, Voltage and Voltage drop. What is the difference between these concepts? ● If it is said that emf produces current flow, then give examples of the various sources of an emf. ● What is the difference between a dynamically induced emf and a statically induced emf? 3 Principles of electricity TVET FIRST Potential difference is represented by the symbol V or PD and is measured in joules per coulomb or volts (V). Definition of coulomb The coulomb is the SI unit of electrical charge equal to the quantity of electricity conveyed in 1 s by a current of 1 A.
eBook - ePubElectrical Engineering
Fundamentals
- Viktor Hacker, Christof Sumereder(Authors)
- 2020(Publication Date)
- De Gruyter Oldenbourg(Publisher)
φ of the field at that point.Defining equation:φ =W pQ +1.9 Voltage V
Voltage is the difference in electric potential between two points. In a static electric field, Voltage is defined as the work needed to move a unit charge between two points.The necessary charge to transport a chargeQ +from object 1 to object 2 equals the difference of the potential energiesof the charges on the two objects.W=1 , 2W−p , 2Wp , 1The potential difference equals the work for the unit charge:Q += 1 A sφ 2−φ 1=WQ1 , 2It is called Voltage V (14 ).Defining equation:V =W1 , 2Q +V = V15 SI unit:V o l tV =JA sThe Voltage between two objects therefore is the work that is necessary to transport the unit chargefrom the negatively charged object to the positively charged object. If this Voltage is expended, the charges are separated.Q += 1A sVoltage can cause electric current: If there is a Voltage between two particles and these two particles are connected through a conductor, current flows. (More specifically: There is an electric field between the two particles. This field exerts force on the free charge carriers, which causes them to move.)Voltage is connected to force:
eBook - PDF- William Moebs, Samuel J. Ling, Jeff Sanny(Authors)
- 2016(Publication Date)
- Openstax(Publisher)
1 V = 1 J/C The familiar term Voltage is the common name for electric potential difference. Keep in mind that whenever a Voltage is quoted, it is understood to be the potential difference between two points. For example, every battery has two terminals, and its Voltage is the potential difference between them. More fundamentally, the point you choose to be zero volts is arbitrary. This is analogous to the fact that gravitational potential energy has an arbitrary zero, such as sea level or perhaps a lecture hall floor. It is worthwhile to emphasize the distinction between potential difference and electrical potential energy. Potential Difference and Electrical Potential Energy The relationship between potential difference (or Voltage) and electrical potential energy is given by (7.5) ΔV = ΔU q or ΔU = qΔV . Voltage is not the same as energy. Voltage is the energy per unit charge. Thus, a motorcycle battery and a car battery can both have the same Voltage (more precisely, the same potential difference between battery terminals), yet one stores much more energy than the other because ΔU = qΔV . The car battery can move more charge than the motorcycle battery, although both are 12-V batteries. Example 7.4 Calculating Energy You have a 12.0-V motorcycle battery that can move 5000 C of charge, and a 12.0-V car battery that can move 60,000 C of charge. How much energy does each deliver? (Assume that the numerical value of each charge is accurate to three significant figures.) Strategy To say we have a 12.0-V battery means that its terminals have a 12.0-V potential difference. When such a battery moves charge, it puts the charge through a potential difference of 12.0 V, and the charge is given a change in potential energy equal to ΔU = qΔV . To find the energy output, we multiply the charge moved by the potential difference. Solution For the motorcycle battery, q = 5000 C and ΔV = 12.0 V .
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- John D. Cutnell, Kenneth W. Johnson, David Young, Shane Stadler(Authors)
- 2021(Publication Date)
- Wiley(Publisher)
19.2 The Electric Potential Difference 583 As used in connection with batteries, the volt is a familiar unit for measuring electric potential difference. The word “volt” also appears in another context, as part of a unit that is used to measure energy, particularly the energy of an atomic particle, such as an electron or a proton. This energy unit is called the electronvolt (eV). Problem-Solving Insight One electron volt is the magnitude of the amount by which the potential energy of an electron changes when the electron moves through a potential difference of one volt. Since the magnitude of the change in potential energy is ∣q 0 ΔV ∣ = ∣(−1.60 × 10 −19 C) × (1.00 V)∣ = 1.60 × 10 −19 J, it follows that 1 eV = 1.60 × 10 −19 J One million (10 +6 ) electron volts of energy is referred to as one MeV, and one billion (10 +9 ) electron volts of energy is one GeV, where the “G” stands for the prefix “giga.” In Equation 19.3, we have seen that the electric potential is the electric poten- tial energy per unit charge. In previous chapters, we have seen that the total energy of an object, which is the sum of its kinetic and potential energies, is an important concept. Its significance lies in the fact that the total energy remains the same (is conserved) during the object’s motion, provided that nonconservative forces, such as friction, are either absent or do no net work. While the sum of the energies at each instant remains constant, energy may be converted from one form to another; for example, gravitational potential energy is converted into kinetic energy as a ball falls. We now include the electric potential energy EPE as part of the total energy that an object can have: E = 1 _ 2 m υ 2 + 1 _ 2 I ω 2 + mgh + 1 _ 2 kx 2 + EPE If the total energy is conserved as the object moves, then its final energy E f is equal to its initial energy E 0 , or E f = E 0 . Example 4 illustrates how the conservation of energy is applied to a charge moving in an electric field.
eBook - PDF- Paul Peter Urone, Roger Hinrichs(Authors)
- 2012(Publication Date)
- Openstax(Publisher)
Electric Potential This is the electric potential energy per unit charge. (19.2) V = PE q Since PE is proportional to q , the dependence on q cancels. Thus V does not depend on q . The change in potential energy ΔPE is crucial, and so we are concerned with the difference in potential or potential difference ΔV between two points, where (19.3) ΔV = V B − V A = ΔPE q . The potential difference between points A and B, V B – V A , is thus defined to be the change in potential energy of a charge q moved from A to B, divided by the charge. Units of potential difference are joules per coulomb, given the name volt (V) after Alessandro Volta. (19.4) 1 V = 1 J C Potential Difference The potential difference between points A and B, V B - V A , is defined to be the change in potential energy of a charge q moved from A to B, divided by the charge. Units of potential difference are joules per coulomb, given the name volt (V) after Alessandro Volta. (19.5) 1 V = 1 J C The familiar term Voltage is the common name for potential difference. Keep in mind that whenever a Voltage is quoted, it is understood to be the potential difference between two points. For example, every battery has two terminals, and its Voltage is the potential difference between them. More fundamentally, the point you choose to be zero volts is arbitrary. This is analogous to the fact that gravitational potential energy has an arbitrary zero, such as sea level or perhaps a lecture hall floor. In summary, the relationship between potential difference (or Voltage) and electrical potential energy is given by (19.6) ΔV = ΔPE q and ΔPE = qΔV . Potential Difference and Electrical Potential Energy The relationship between potential difference (or Voltage) and electrical potential energy is given by (19.7) ΔV = ΔPE q and ΔPE = qΔV . The second equation is equivalent to the first. Voltage is not the same as energy.
eBook - PDF- Richard C. Dorf, James A. Svoboda(Authors)
- 2020(Publication Date)
- Wiley(Publisher)
The value of a Voltage may be positive or negative. The direction of a Voltage is given by its polarities ( , ). As a matter of vocabulary, we say that a Voltage exists across an element. Figure 1.4-1 shows that there are two ways to label the Voltage across an element. The Voltage v ba is proportional to the work required to move a positive charge from terminal a to terminal b. On the other hand, the Voltage v ab is proportional to the work required to move a positive charge from terminal b to terminal a. We sometimes read v ba as “the Voltage at terminal b with respect to terminal a.” Similarly, v ab can be read as “the Voltage at terminal a with respect to terminal b.” Alternatively, we sometimes say that v ba is the Voltage drop from terminal a to terminal b. The Voltages v ab and v ba are similar but different. They have the same magnitude but different polarities. This means that v ab v ba When considering v ba , terminal b is called the “ terminal” and terminal a is called the “ terminal.” On the other hand, when talking about v ab , terminal a is called the “ terminal” and terminal b is called the “ terminal.” The Voltage across an element is the work (energy) required to move a unit positive charge from the terminal to the terminal. The unit of Voltage is the volt, V. The equation for the Voltage across the element is v dw dq 1 4-1 where v is Voltage, w is energy (or work), and q is charge. A charge of 1 coulomb delivers an energy of 1 joule as it moves through a Voltage of 1 volt. 1.5 P o w e r a n d E n e r g y The power and energy delivered to an element are of great importance. For example, the useful output of an electric lightbulb can be expressed in terms of power. We know that a 300-watt bulb delivers more light than a 100-watt bulb. Power is the time rate of supplying or receiving energy. Thus, we have the equation p dw dt 1 5-1 v ba b a – – + + v ab FIGURE 1.4-1 Voltage across a circuit element. Power and Energy 7
eBook - PDF- John D. Cutnell, Kenneth W. Johnson, David Young, Shane Stadler(Authors)
- 2015(Publication Date)
- Wiley(Publisher)
19.2 The Electric Potential Difference The electric potential V at a given point is the electric potential energy of a small test charge q 0 situated at that point divided by the charge itself, as shown in Equation 19.3. The SI unit of electric potential is the joule per coulomb (J/C), or volt (V). The electric potential difference between two points A and B is given by Equation 19.4. The potential difference between two points (or between two equipotential surfaces) is often called the “Voltage.” W AB 5 EPE A 2 EPE B (19.1) V 5 EPE q 0 (19.3) V B 2 V A 5 EPE B q 0 2 EPE A q 0 5 2W AB q 0 (19.4) Focus on Concepts 535 FOCUS ON CONCEPTS Note to Instructors: The numbering of the questions shown here reflects the fact that they are only a representative subset of the total number that are available online. However, all of the questions are available for assignment via an online homework management program such as WileyPLUS or WebAssign. Section 19.2 The Electric Potential Difference 2. Two different charges, q 1 and q 2 , are placed at two different locations, one charge at each location. The locations have the same electric poten- tial V. Do the charges have the same electric potential energy? (a) Yes. If the electric potentials at the two locations are the same, the electric potential energies are also the same, regardless of the type (1 or 2) and magnitude of the charges placed at these locations. (b) Yes, because elec- tric potential and electric potential energy are just different names for the same concept. (c) No, because the electric potential V at a given location depends on the charge placed at that location, whereas the electric poten- tial energy EPE does not. (d) No, because the electric potential energy EPE at a given location depends on the charge placed at that location as well as the electric potential V. 4. A proton is released from rest at point A in a constant electric field and accelerates to point B (see part a of the drawing).
eBook - PDF- John D. Cutnell, Kenneth W. Johnson, David Young, Shane Stadler(Authors)
- 2018(Publication Date)
- Wiley(Publisher)
Conversely, a negative charge accelerates from a region of lower potential toward a region of higher potential. An electron volt (eV) is a unit of energy. The relationship between elec- tron volts and joules is 1 eV = 1.60 × 10 −19 J. The total energy E of a system is the sum of its translational ( 1 2 mυ 2 ) and rotational ( 1 2 Iω 2 ) kinetic energies, gravitational potential energy (mgh), elas- tic potential energy ( 1 2 kx 2 ), and electric potential energy (EPE), as indicated by Equation 1. If external nonconservative forces like friction do no net work, the total energy of the system is conserved. That is, the final total energy E f is equal to the initial total energy E 0 ; E f = E 0 . E = 1 2 mυ 2 + 1 2 Iω 2 + mgh + 1 2 kx 2 + EPE (1) 19.3 The Electric Potential Difference Created by Point Charges The electric potential V at a distance r from a point charge q is given by Equation 19.6, where k = 8.99 × 10 9 N · m 2 /C 2 . This expression for V assumes that the electric potential is zero at an infinite distance away from the charge. The total electric potential at a given location due to two or more charges is the algebraic sum of the potentials due to each charge. V = kq r (19.6) The total potential energy of a group of charges is the amount by which the electric potential energy of the group differs from its initial value when the charges are infinitely far apart and far away. It is also equal to the work required to assemble the group, one charge at a time, starting with the charges infinitely far apart and far away. 19.4 Equipotential Surfaces and Their Relation to the Electric Field An equipotential surface is a surface on which the electric potential is the same everywhere. The electric force does no work as a charge moves on an equipotential surface, because the force is always perpendicular to the dis- placement of the charge.
- Jerry D. Wilson, Anthony J. Buffa, Bo Lou(Authors)
- 2022(Publication Date)
- CRC Press(Publisher)
Δ = Δ + V U q e (16.1) • The electric potential difference between two parallel plates is Δ = V Ed (parallel plates) (16.2) • Equipotential surfaces (also equipotentials ) are of constant electric potential. These surfaces are everywhere perpen- dicular to the electric field. • The electric potential difference between two locations near a point charge is Δ = − V kq r kq r B A (16.3) • The electric potential near a point charge (choosing zero reference at infinite distance) is V kq r = (16.4) • The electric potential energy of two point charges (choosing U = 0 at r = ∞) is U kq q r 12 1 2 12 = (16.5) • The electric potential energy of more than two point charges is the sum of point charge pair terms from Equation 16.5: U U U U U = + + + 12 23 13 14 (16.6) 436 College Physics Essentials • The electric field E ( ) is in the direction of the most rapid decrease in electric potential (V). The field magnitude (E) is the maximum rate of change of the potential with distance, or E V x = Δ Δ max (16.8) • The electron-volt (eV) is the kinetic energy gained by an electron or a proton accelerated through a potential difference of 1 V. The conversion factor to SI units is 1 eV = 1.60 × 10 −19 J. • A capacitor is any arrangement of two metallic plates that can store charge and energy. Its capacitance is a measure of how effective it is in storing charge and is defined as the magnitude of the charge stored on either plate per volt: C Q V = Δ (16.9) • The expression for the capacitance of a parallel plate capacitor (in air) is C A d = ε o (16.12) where ε o = 8.85 × 10 −12 C 2 /(N·m 2 ) is the permittivity of free space. • The energy stored in a capacitor depends on its capaci- tance and the charge the capacitor stores (or, equivalently, the Voltage across its plates). There are three equivalent expressions for this energy: U Q V Q C C V C = ⋅ = = 1 2 2 1 2 2 2 Δ Δ ( ) (16.13) • A dielectric is a non-conducting material that increases capacitance.
Index pages curate the most relevant extracts from our library of academic textbooks. They’ve been created using an in-house natural language model (NLM), each adding context and meaning to key research topics.
