...Chapter 17 Electric Potential Units of Chapter 17 • Electric Potential Energy and Potential Difference •Relation between Electric Potential and Electric Field •Equipotential Lines and surfaces •The Electron Volt, a Unit of Energy •Electric Potential Due to Point Charges •Potential Due to Electric Dipole; Dipole Moment •Capacitance, Dielectrics and Storage of Electric Energy Electrostatic Potential Energy and Potential Difference The electrostatic force is conservative – potential energy can be defined as ΔPE= -W Change in electric potential energy is negative of work done by electric force: W =Fd=qEd Electric potential is defined as potential energy per unit charge: Unit of electric potential: the volt (V). 1 V = I J/C. Only changes in potential can be measured, Electrostatic Potential Energy and relation between Electric potential and Electric field Analogy between gravitational and electrical potential energy: Work is charge multiplied by potential: Work is also force multiplied by distance: If the field is not uniform, it can be calculated at multiple points: Solving problems Example 17-2: suppose an electron in a picture tube of television set is acclerated from rest through a potential difference of Vb-Va = Vba = + 50000V. (a) What is the change in electric potential energy of the electron? (b) What is the speed of the electron as a result of this acceleration? Equipotential Lines Electric potential can be represented with diagram...
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...phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire. In addition, electricity encompasses less familiar concepts such as the electromagnetic field and electromagnetic induction. The word is from the New Latin ēlectricus, "amber-like"coined in the year 1600 from the Greek ήλεκτρον (electron) meaning amber(hardened plant resin), because static electricity effects were produced classically by rubbing amber. Usage In general usage, the word "electricity" adequately refers to a number of physical effects. In scientific usage, however, the term is vague, and these related, but distinct, concepts are better identified by more precise terms: * Electric charge: a property of some subatomic particles, which determines their electromagnetic interactions. Electrically charged matter is influenced by, and produces, electromagnetic fields. * Electric current: a movement or flow of electrically charged particles, typically measured in amperes. * Electric field: an influence produced by an electric charge on other charges in its vicinity. * Electric potential: the capacity of an electric field to do work on an electric charge, typically measured in volts. * Electromagnetism: a fundamental interaction between the magnetic field and the presence and motion of an electric charge. The most common use of the word "electricity"...
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...by an external agent from the work-energy principle: W = ®KE + ®PE = 0 + q(Vb – Va) = (– 8.6 × 10–6 C)(+ 75 V – 0)= – 6.5 × 10–4 J (done by the field). 2. We find the work done by an external agent from the work-energy principle: W = ®KE + ®PE = 0 + q(Vb – Va) – 2.40 × 10–17 J (done by the field); = (1.60 × 10–19 C)[(– 50 V) – (+ 100 V)] = W = q(Vb – Va) – 150 eV. = (+ 1 e)[(– 50 V) – (+ 100 V)] = 3. Because the total energy of the electron is conserved, we have ®KE + ®PE = 0, or ®KE = – q(VB – VA) = – (– 1.60 × 10–19 C)(21,000 V) = 3.4 × 10–15 J; 21 keV. ®KE = – (– 1 e)(21,000 V) = 4. Because the total energy of the electron is conserved, we have ®KE + ®PE = 0; ®KE + q(VB – VA) = 0; 3.45 × 10–15 J + (– 1.60 × 10–19 C)(VB – VA); which gives VB – VA = Plate B is at the higher potential. 2.16 × 103 V. 5. For the uniform electric field between two large, parallel plates, we have 4.2 × 104 V/m. E = ®V/d = (220 V)/(5.2 × 10–3 m) = 6. For the uniform electric field between two large, parallel plates, we have E = ®V/d; 640 V/m = ®V/(11.0 × 10–3 m), which gives ®V = 7.04 V. 7. Because the total energy of the helium nucleus is conserved, we have ®KE + ®PE = 0; ®KE + q(VB – VA) = 0; 65.0 keV + (+ 2e)(VB – VA); which gives VB – VA = – 32.5 kV. 8. For the uniform electric field between two large, parallel plates, we have E = ®V/d; 3 × 106 V/m = (100 V)/d, which gives d = 3 × 10–5 m. 9. We use the work-energy principle: W = ®KE + ®PE = ®KE + q(Vb...
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...particles is integral to the understanding of electrical forces. The lesson begins with traditional activities of charging objects by friction and comparing electrostatic forces to magnetostatic forces. The traditional experiments are explained in terms of the model of an atom, and the “attract and repel force rules” are explored and expanded. Devices to create, store, and measure charge are utilized in experiments. The formal theory of Coulomb’s law is introduced, and problems are assigned utilizing that theory. Elements of the historical development of electrostatics and planetary model of the atom are researched, and students have an assignment describing contributions of historically important scientists. Additional concepts of electric fields, potential difference, and properties of conductors and insulators are developed through experiment, demonstration, and discussion. TEKS: |P.5 |The student knows the nature of forces in the physical world. The student is expected to: | |P.5A |Research and describe the historical development of the concepts of gravitational, electromagnetic, weak nuclear and strong nuclear | | |forces. Supporting Standard | |P.5C |Describe and calculate how the magnitude of the electrical force between two objects depends on their charges and the distance | |...
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...Energy can be converted from one form into another in three basic ways know as the action of force. The first one is gravitational forces which is when gravity accelerates a falling object, its converts its potential energy to kinetic energy. Likewise, when an object is lifted the gravitational field stores the energy exerted by the lifter as potential energy in the earth-object system. The second one is electric and magnetic force fields which is charged particles, upon which electrical fields exert forces, possess potential energy in the presence of an electric field in a way similar to that of an object in a gravitational field. These force fields can accelerate particles, converting a particle's potential energy into kinetic energy. Particles can interact via the electric and magnetic fields they create, transferring energy between them, and in the case of an electrical current in a conductor, cause molecules to vibrate, for example converting electrical potential energy into heat. This leads to the third action of force which is frictional forces(www.powerincooperation.com)This is defined as macroscopic energy of an object, that is, the potential and kinetic energy associated with the position, orientation, or motion of the entire object, not counting the thermal or heat energy of the system, can be converted into heat, whenever the object slides against another object. The sliding causes the molecules on the surfaces of contact to interact via electromagnetic fields with...
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...PHYSICS FORMULAS 2426 Electron = -1.602 19 × 10-19 C = 9.11 × 10-31 kg Proton = 1.602 19 × 10-19 C = 1.67 × 10-27 kg Neutron = 0 C = 1.67 × 10-27 kg 23 6.022 × 10 atoms in one atomic mass unit e is the elementary charge: 1.602 19 × 10-19 C Potential Energy, velocity of electron: PE = eV = ½ 2 mv 1V = 1J/C 1N/C = 1V/m 1J = 1 N·m = 1 C·V 1 amp = 6.21 × 1018 electrons/second = 1 Coulomb/second 1 hp = 0.756 kW 1 N = 1 T·A·m 1 Pa = 1 N/m2 Power = Joules/second = I2R = IV [watts W] Quadratic Kinetic Energy [J] − b ± b 2 − 4ac x= Equation: KE = 1 mv 2 2 2a [Natural Log: when eb = x, ln x = b ] n: 10-9 p: 10-12 m: 10-3 µ: 10-6 f: 10-15 a: 10-18 Rectangular Notation: Z = R ± jX where +j represents inductive reactance and -j represents capacitive reactance. For example, Z = 8 + j 6Ω means that a resistor of 8Ω is in series with an inductive reactance of 6Ω. Polar Notation: Z = M ∠θ, where M is the magnitude of the reactance and θ is the direction with respect to the horizontal (pure resistance) axis. For example, a resistor of 4Ω in series with a capacitor with a reactance of 3Ω would be expressed as 5 ∠-36.9° Ω. In the descriptions above, impedance is used as an example. Rectangular and Polar Notation can also be used to express amperage, voltage, and power. To convert from rectangular to polar notation: Given: X - jY (careful with the sign before the ”j”) Magnitude: Angle: Addition of Multiple Vectors: r r r r R = Ar+ B + C r Resultant = Sum of the vectors r r Rx...
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...Resistance and Electromotive Force - Current - Resistivity - Resistance - Electromotive Force and Circuits Current Electric current: charges in motion from one region to another. Electric circuit: conducting path that forms a closed loop in which charges move. In these circuits, energy is conveyed from one place to another. Electrostatics: E = 0 within a conductor _ Current (I) = 0, but not all charges are at rest, free electrons can move (v ~ 106 m/s). Electrons are attracted to + ions in material _ do not escape. Electron motion is random _ no net charge flow Non-electrostatic: E ≠ 0 inside conductor _ F = q E Charged particle moving in vacuum _ steady acceleration // F Charged particle moving in a conductor _ collisions with “nearly” stationary massive ions in material change random motion of charged particles. Due to E, superposition of random motion of charge + slow net motion (drift) of charged particles as a group in direction of F = q E _ net current in conductor. Drift velocity (vd) = 10-4 m/s (slow) Direction of current flow: - In the absence of an external field, electrons move randomly in a conductor. If a field exists near the conductor, its force on the electron imposes a drift. - E does work on moving charges _ transfer of KE to the conductor through collisions with ions _ increase in vibrational energy of ions _ increase T. - Much of W done by E goes into heating the conductor, not into accelerating charges faster and faster...
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...Figure 1.1: Ionization and Recombination Ionization has a threshold energy. Recombination has not but is much less probable. Threshold is ionization energy (13.6eV, H). χi | Figure 1.2: Ionization and radiative recombination rate coefficients for atomic hydrogen Integral over Maxwellian distribution gives rate coefficients (reaction rates). Because of the tail of the Maxwellian distribution, the ionization rate extends below T = χi. And in equilibrium, when | nionsnneutrals | = | < σi v >< σr v > | , | | (1.1) | the percentage of ions is large ( ∼ 100%) if electron temperature: Te >~χi/10. e.g. Hydrogen is ionized for Te >~1eV (11,600°k). At room temp r ionization is negligible. For dissociation and ionization balance figure see e.g. Delcroix Plasma Physics Wiley (1965) figure 1A.5, page 25. 1.1.2 Plasmas are Quasi-Neutral If a gas of electrons and ions (singly charged) has unequal numbers, there will be a net charge density, ρ. ρ = ne(−e) + ni(+e) = e (ni − ne) | | (1.2) | This will give rise to an electric field via ∇ . E= | ρϵ0 | = | eϵ0 | (ni − ne) | | (1.3) | Example: Slab. | Figure 1.3: Charged slab | | dEdx | | | = | | | ρϵ0 | | | | (1.4) | | → E | | = | | ρ | xϵ0 | | | | (1.5) | | This results in a force on the charges tending to expel whichever species is in excess. That is, if ni > ne, the E field causes ni to decrease, ne to increase tending to reduce the charge...
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...thickness or width of the dielectric material and is measured in terms of volts per meter. Dielectric Relaxation The effect on the dipole moment when the when the dielectric substance is removed form electric field after a long time application of the electric field so that the dielectric substance is fully polarized. When the dielectric substance is place in the Electric Filed the material gets polarized so that their electric field of all the dipoles will be in the same direction now if we remove the electric field then the arrangement of the molecules, their electric field direction, and the dipole moment of the molecules starts changing because of the collision and the random motion of the molecules and this disorientation occurs exponentially which depend on the properties of the material Dipolar polarization fails to follow the external electric field frequency starting for the micro wave frequencies (〖10〗^11). Ionic polarization fails to compete the external electric field frequency form far...
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...study………………………………………….…..3 * Scope and Delimitation………………………………………………..3 II. REVIEW OF RELATED LITERATURE…………………………………….4 * Definition of Term……………………………………………….…....7 III. METHODOLOGY……………………………………………………….…...8 IV. RESULTS AND DISCUSSION …………………………………………….12 V. CONCLUSION/ RECOMMENDATION…………………………………...13 BIBLIOGRAPHY……………………………………………………………iii ABSTRACT This study aims to evaluate the potential of magnet size in producing electricity. This magnet producing electricity was conducted to make a substitute light in case of urgent situation as a replacement for using flashlight that needs batteries. The researchers assembled the electric generator by inserting magnet in hollow ended-box. Poke a hole in center of the box using a nail. At this point you should let four magnets clamps themselves around the nail. Coil the magnet wire around the box. Put each end of the wire to the bulb. Test and analysis were done to test the stability of the product. It was verified that Set-up C can produce greater electricity. As a conclusion, the higher the magnetic field the higher the electricity produces. This study needs further investigation for better improvement. You can also study effects of metals in producing...
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...rates have been observed to depend on aspect ratio ~ depth/width ! rather than the absolute feature size. 1 Several mechanisms have been invoked to explain the ‘‘rule’’ of aspect-ratio-dependent etching ~ ARDE ! , but no general theory has emerged that captures the variety of seemingly conflicting experimental observations reported in the literature. 1,2 For example, while an ion-neutral synergy model with pure neutral flux shadowing appears to be con- sistent with a wealth of ARDE measurements in semiconductors, 2 it does not hold for the etching of insula- tors. Indeed, Doemling et al. 3 have reported inverse ARDE of trenches and holes in SiO 2 in a high-density CHF 3 plasma at 20 mTorr. Remarkably, they also reported aspect ratio independent etching ~ ARIE ! when the pressure was lowered to 6.7 mTorr; for fixed etching time, the etch depth was the same for a variety of trench widths and hole diameters ~ as low as 0.25 m m, corresponding to an aspect ratio of 8.5:1 ! . These authors convincingly argued that the strong influence of feature geometry on neutral flux of an etch inhibitor, pro- duced in the CHF 3 plasma, is responsible for the inverse ARDE at the higher pressure. The low pressure results were explained by hypothesizing that the neutral density at the bottom of the trench or hole, while ‘‘too low to cause inverse ARDE, it was still sufficient to suppress regular ARDE.’’ This hypothesis must be valid for all trenches and holes etched at the low pressure, which spanned...
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...Assignment 1 Energy can be converted from one form into another in three basic ways know as the action of force. The first one is gravitational forces which is when gravity accelerates a falling object, its converts its potential energy to kinetic energy. Likewise, when an object is lifted the gravitational field stores the energy exerted by the lifter as potential energy in the earth-object system. The second one is electric and magnetic force fields which is charged particles, upon which electrical fields exert forces, possess potential energy in the presence of an electric field in a way similar to that of an object in a gravitational field. These force fields can accelerate particles, converting a particle's potential energy into kinetic energy. Particles can interact via the electric and magnetic fields they create, transferring energy between them, and in the case of an electrical current in a conductor, cause molecules to vibrate, for example converting electrical potential energy into heat. This leads to the third action of force which is frictional forces(www.powerincooperation.com)This is defined as macroscopic energy of an object, that is, the potential and kinetic energy associated with the position, orientation, or motion of the entire object, not counting the thermal or heat energy of the system, can be converted into heat, whenever the object slides against another object. The sliding causes the molecules on the surfaces of contact to interact via electromagnetic...
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...body to store an electrical charge. Drift Velocity- the flow velocity that a particle, such as an electron, attains in a material due to an electric field. Electric circuit- A path in which electrons from a voltage or current source flow Electric current- a flow of electric charge Electric potential- he amount of electric potential energy that a unitary point electric charge would have if located at any point in space. Energy- property of objects which can be transferred to other objects and converted into different forms. Parallel circuit- has two or more paths for current to flow through. Voltage is the same across each component of the parallel circuit Potential difference- the difference of electric potential between two points. Resistance- the degree to which a substance or device opposes the passage of an electric current, causing energy dissipation. Ohm's law resistance (measured in ohms) is equal to the voltage divided by the current. Schematic diagram- A schematic, or schematic diagram, is a representation of the elements of a system using abstract, graphic symbols rather than realistic pictures. A schematic usually omits all details that are not relevant to the information the schematic is intended to convey, and may add unrealistic elements that aid comprehension Series circuit- In a series circuit, the current through each of the components is the same, and the voltage across the circuit is the sum of the voltages across each component. In a parallel circuit...
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...VASILEIOS-MARIOS GKORTSAS vasilisg@mit.edu 6.638 Term Paper Attosecond Pulse Generation Abstract: The word “attosecond” (1 as = 10-18 sec) entered the vocabulary of physics when sub-femtosecond pulses of UV/XUV light were established. High harmonic generation (HHG) is currently the only experimentally proven method for generating attosecond pulses. Attosecond science has opened the door to real-time observation and time-domain control of atomic-scale electron dynamics. In this work, we review the essentials of the generation of attosecond pulses and we mention the applications of attosecond science in the control of electronic motion. 1. Introduction The need for finer time resolution and the quest for higher peak power explain the continuous trend towards shorter laser pulses since the invention of the laser. The historical progress of ultra-short technology is summarized in Figure 1. The first pulse lasers had duration of several hundreds of microseconds. The invention of Q-switching (Hellwarth, 1961) reduced the pulse length to 10 ns (four orders of magnitude decrease). The invention of laser mode locking (DiDomenico, 1964; Hargrove et al., 1964; Siegman, 1970) accompanied by broad gain laser media (Shank and Ippen 1974) further reduced the duration to less than 1 ps (another four orders of magnitude decrease). The ring cavity with intra-cavity prism compensation of the group velocity dispersion produced pulses of 6 fs (Fork et al, 1987)...
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...*Physics Prelims (1-7).qxd 12/11/08 1:00 PM Page 1 SCIENCE VISUAL RESOURCES PHYSICS An Illustrated Guide to Science The Diagram Group *Physics Prelims (1-7).qxd 12/11/08 1:00 PM Page 2 Physics: An Illustrated Guide to Science Copyright © 2006 The Diagram Group Author: Derek McMonagle BSc PhD CSci CChem FRSC Editors: Catherine Gaunt, Jamie Stokes Design: Anthony Atherton, Richard Hummerstone, Lee Lawrence, Tim Noel-Johnson, Phil Richardson Illustration: Peter Wilkinson Picture research: Neil McKenna Indexer: Martin Hargreaves All rights reserved. No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval systems, without permission in writing from the publisher. For information contact: Chelsea House An imprint of Infobase Publishing 132 West 31st Street New York NY 10001 For Library of Congress Cataloging-in-Publication Data, please contact the Publisher ISBN 0-8160-6167-X Chelsea House books are available at special discounts when purchased in bulk quantities for businesses, associations, institutions, or sales promotions. Please call our Special Sales Department in New York at 212/967-8800 or 800/322-8755. You can find Chelsea House on the World Wide Web at http://www.chelseahouse.com Printed in China CP Diagram 10 9 8 7 6 5 4 3 2 This book is printed on acid-free paper. *Physics Prelims (1-7).qxd 12/11/08 1:00 PM Page...
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