Chapter 18 Electrical Energy and Capacitance. 18.1 Electrical Potential Energy Objectives 1. Define electrical potential energy 2. Compare the electrical.

Slides:



Advertisements
Similar presentations
Electric Energy and Circuits. Electrostatic Equilibrium No net motion of charge is occurring within a conductor Meets the following conditions ▫Electric.
Advertisements

Physics 152 Walker, Chapter 20 Electrostatic Potential Energy Electrostatic Potential.
Electric Energy and Current Chapter 17 Electrical Potential Energy- the potential energy between charges at a distance, or between a charge and an electric.
Electric Potential Chapter 23 opener. We are used to voltage in our lives—a 12-volt car battery, 110 V or 220 V at home, 1.5 volt flashlight batteries,
Electric Energy and Current Chapter 18 Electrical Potential Energy- the potential energy between charges at a distance, or between a charge and an electric.
17-7 Capacitance A device that stores electric charge Two plates that are separated by an insulator Used in electronic circuits Store charge that can later.
1 Capacitance and Dielectrics Chapter 27 Physics chapter 27.
Electric Fields. What is an Electric Field? An electric field is a region of space surrounding a charged object. A stationary object experiences an electric.
Chapter 18 Electric Energy and Capacitance demonstrations.
Norah Ali Al-moneef king saud university
Copyright © 2009 Pearson Education, Inc. Lecture 4 – Electricity & Magnetism b. Electric Potential.
Chapter 18 – Electric Potential and Capacitance Section 1 Electric Potential Energy.
Lecture 3 Electrical Energy Chapter 16.1  16.5 Outline Potential Difference Electric Potential Equipotential Surface.
Chapter 24 Capacitance, Dielectrics, Electric Energy Storage
Electric Energy and Capacitance
Electrical Energy and Capacitance
Electrical Energy & Current. Introduction to Electric PE, Electric Potential, and Potential Difference Intro to Electric Potential.
Electrical Energy and Capacitance. Electrical Potential Energy Potential energy associated with the electrical force between two charges Form of mechanical.
Copyright © 2009 Pearson Education, Inc. Various Capacitors Chapter 24 : Capacitance & Dielectrics. (in the book by Giancoli). Chapter 26 in our book.
AP PHYSICS UNIT 8 GIANCOLI CH.16 & 17 Electric Charge, Fields and Potential.
Welcome to Physics Jeopardy Chapter 17 Final Jeopardy Question Electric Current Circuits 100 Capacitance Voltage
Electric Potential Difference. Electric Potential Energy (PE) Potential energy associated with a charged object due to its position relative to a source.
1 Electric Potential Reading: Chapter 21 Chapter 21.
Preview Statics Circuits Electricity and Magnetism Chapter 16 Section 1 Electric Charge.
Review. Coulomb’s Law Units of Charge 1 Coulomb (C)
 As you lift an object off the ground, you are increasing its potential energy  Same is for electric potential ◦ Electric potential ( Δ V)  Work done.
e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- p+p+ p+p+ p+p+ Connecting two parallel plates to a battery produces uniform electric field  the electric.
ELECTRIC POTENTIAL ENERGY AND ELECTRIC POTENTIAL POTENTIAL ENERGY ELECTRIC POTENTIAL WORK-ENERGY THEOREM CAPACITANCE COMBINATIONS OF CAPACITORS STORED.
Electric Energy and Capacitance
Electrical Potential Energy
Chapter 18.2 Review Capacitance and Potential. 1. A 5 μF capacitor is connected to a 12 volt battery. What is the potential difference across the plates.
The Electric Potential
Copyright © 2009 Pearson Education, Inc. Chapter 23 Electric Potential.
Electrostatic Forces Homework: Complete handout. Magnitude of Force According to Coulomb’s Law  The magnitude of force exerted on a charge by another.
Chapter 16 Electrical Energy and Capacitance. Objectives Electrical potential Electric Potential from a Point Charge Electron Volt Capacitance Parallel.
Obtaining Electric Field from Electric Potential Assume, to start, that E has only an x component Similar statements would apply to the y and z.
Static Electricity, Electric Forces, Electric Fields, Electric Potential Energy, Electric Potential, Capacitors.
The forces between electrical charges have an electrical potential energy associated with this force. The total ME = KE + gravitational PE + elastic PE.
Electric Potential & Electric Potential Energy. Electric Potential Energy The electrostatic force is a conservative (=“path independent”) force The electrostatic.
Physics II, Pg 1 AP Physics Today’s Agenda AP Physics Today’s Agenda l CHAPTER 16 - ELECTRIC POTENTIAL AND ELECTRIC ENERGY; CAPACITANCE l Chp 16 problems.
Electric Fields and Forces
Electric Potential and Energy. Objectives Define work and relate it to energy Define electric potential difference, and relate it to the work done on.
Electrical Energy and Capacitance Physics - Chapter 18.
Electric field, Electric Potential Difference and Capacitance.
CHAPTER 26 : CAPACITANCE AND DIELECTRICS
© Houghton Mifflin Harcourt Publishing Company Preview Objectives Electrical Potential Energy Potential Difference Sample Problem Chapter 17 Section 1.
Parallel Plates.
Static Electricity, Electric Forces, Electric Fields
Electrical Energy and Capacitance
An electric force of 4.5 x N is measured between two particles. One particle has a charge of 2.0 x C & the other has a charge of 3.0 x
Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 18 Electric Energy and Current Chapter 18.
Static Electricity, Electric Forces, Electric Fields.
The basic components of an atom are:  Protons  Electrons  Neutrons Atoms are held together by electric force. Electric force is one of the most powerful.
Static Electricity, Electric Forces, Electric Fields.
Chapter 18: Electrical Energy and Capacitance. Section 18-1: Electrical Potential Energy When two charges interact, there is an electric force between.
Chapter 13 Electric Energy and Capacitance. Electric Potential Energy The electrostatic force is a conservative force It is possible to define an electrical.
Electric Energy and Capacitance
Chapter 18.2 Capacitance and Potential
Electric Potential Energy and Potential Difference
Electrical Energy, Potential and Capacitance
Electrical Energy and Potential
Section 1 Electric Potential
Electrical Energy and Current
Chapter 18: Electrical Potential Energy
Electric Energy and Current
Electrical Energy & Capacitance Pgs
Static Electricity, Electric Forces, Electric Fields, Electric Potential Energy, Electric Potential, Capacitors.
Electrical Energy and Current
Section 2: Applications of Electric Fields
Static Electricity, Electric Forces, Electric Fields, Electric Potential Energy, Electric Potential, Capacitors.
Presentation transcript:

Chapter 18 Electrical Energy and Capacitance

18.1 Electrical Potential Energy Objectives 1. Define electrical potential energy 2. Compare the electrical potential energy for various charge distributions

A Look Back at Gravitational Potential Energy PE grav =mgh h PE grav =mgh PE grav =0

Electric Potential Energy Potential associated with an object due to its position relative to a source of electric force

Consider: Uniform Electric Field

If the charge is moving…. + Charge - Charge With ELoses PE electric Gains PE electric Opposite EGains PE electric Loses PE electric Charge Movement in E Field vs PE electric

Electrical Potential Energy PE electric = -qEd q = charge (C) E = electric field strength (N/C) d = displacement (m) from the reference point in the direction of the field (in a uniform field)

Electrical Potential Energy for a Pair of Charges PE electric = k C q 1 q 2 r …because point charges produce non-uniform electric fields

Regarding PE electric for point charges… The reference point for electrical potential energy is assumed to be at infinity. Note that PE electric goes to zero as r goes to infinity. Because like charges repel, positive work must be done to bring them together. So, PE electric is positive for like charges and negative for unlike charges. For determining PE electric for more than two charges, calculate PE electric for each pair then add the energies.

Problem: In one model of the hydrogen atom, an electron in its lowest energy state moves in a circular orbit about the nucleus (a single proton) at a distance of 5.29x m. Find the electrical potential energy of the hydrogen atom. Which equation for PE electric ? PE electric = k C q 1 q 2 r Answer: PE electric = -4.35x J

18.2 Potential Difference Objectives 1.Distinguish between electrical potential energy, electric potential, and potential difference. 2.Compute the potential difference for for various charge distributions.

Water Analogy

Electric Potential V = PE electric q …is the electrical potential energy associated with a charged particle divided by the charge of the particle

Potential Difference …is the change in electrical potential energy associated with a charged particle divided by the charge of the particle. V =PE electric q units = J/C = volts (V)

What’s another name for PE? Hint:What do we have to do to a particle if we want to increase it’s PE? PE aka “Work” (W) So, ΔV = PEelec = W q q units for PE and for work = joules (J)

Potential difference is often referred to as “voltage”. As a 1C charge moved through a potential difference of 1V, the charge gains (or loses) 1J of energy. Common potential differences (voltages) are 12V for a car battery and 120V between the two slots in a household electrical outlet. More About Potential Difference

Potential Difference in a Uniform Electric Field And PE electric = -qEd (uniform field) V =We know PE electric q SoV = -qEd q dV = -E (where d is displacement from a reference point in the direction of the electric field)

Notice…..new units for E !! V units is volts (V) d is in meters (m)...therefore E units must be ?? V = -Ed E is in V/m

Potential Difference at Some Location Near a Point Charge PE electric q We know And PE electric = k C q 1 q 2 (for point charges) r V = k C q 1 q 2 q 1 r So V = k C q r V = (compares the potential difference between a point at infinity and some location near a point charge)

Questions 1. Find the potential difference between a point infinitely far away from and a point 1.0 cm from a proton. 2. A proton is released from rest in a uniform E- field with a magnitude of 8.0x10 4 V/m. The proton moves 0.50 m as a result. Find: a) The potential difference between the initial and final positions of the proton. b) The change in electrical potential energy of the proton as a result of this displacement.

Answers x V 2.a) -4.0 x 10 4 V b) -6.4 x J

PE electric, Electric Potential, and Potential Difference in a Battery The potential difference between the positive and negative terminals is 9V, where the electric potential at the negative terminal is 0V, and the electric potential at the positive terminal is 9V. When hooked to an electrical device, the charge moves inside the battery from negative to positive terminal. The battery does work on the charge in order to move it from the (-) to the (+) terminal, so PE electric increases.

More on PE electric, Electric Potential and Potential Difference

18.3 Capacitance Objectives 1.Relate capacitance to the storage of electrical potential energy in the form of separated charges 2.Calculate the capacitance of various devices 3.Calculate the energy stored in a capacitor

Capacitance …is the ability of a conductor to store energy in the form of electrically separated charges

Parallel-plate Capacitor Parallel conductive plates in a circuit with a charge source (V). Close the switch and the charge flows until the voltage across the plates equals the applied voltage. Charge flows from one plate to the other, leaving behind a plate that is equally (but oppositely) charged. Open the switch and charge (and electrical potential energy) are stored.

Capacitance – Basic Equation C = Q V capacitance = magnitude of charge on each plate potential difference C = farads (F) = C/V

Capacitance and PE electric PE electric = ½ QV and since C = Q V substituting gives us: PE electric = ½ CV2V2 and PE electric = Q 2 2C

Questions 1. A parallel-plate capacitor has a charge of 6.0x10 -6 C when charged by a potential difference of 1.25V. a) Find its capacitance b) How much potential energy is stored when this capacitor is connected to a 1.5V battery? Answers:a)4.8x10 -6 F b)5.4x10 -6 J