Chapter 8. Capacitors. Charging a capacitor


 Jeffery Briggs
 3 years ago
 Views:
Transcription
1 Chapter 8 Capacitors You can store energy as potential energy by pulling a bowstring, stretching a spring, compressing a gas, or lifting a book. You can also store energy as potential energy in an electric field, and a capacitor is a device you can use to do exactly that. There is a capacitor in a portable batteryoperated photoflash unit, for example. It accumulates charge relatively slowly during the charging process, building up an electric field as it does so. It holds this field and its energy until the energy is rapidly released during the flash. Charging a capacitor One way to charge a capacitor is to place it in an electric circuit with a battery. An electric circuit is a path through which charge can flow. A battery is a device that maintains a certain potential difference between its terminals (points at which charge can enter or leave the battery) by means of internal electrochemical reactions. In Fig. 8.1a, a battery B, a switch S, an uncharged capacitor C, and interconnecting wires form a circuit. The same circuit is shown in the schematic diagram of Fig. 8.1b, in which the symbols for a battery, switch, and a capacitor represent those devices. The battery maintains potential difference V between its terminals. The terminal of higher potential is labelled + and is often called the positive terminal; the terminal of lower potential is labelled  and is often called the negative terminal. 54
2 55 Figure 8.1: (a) Battery B, switch S, and plates h and l of capacitor C, connected in a circuit. (b) A schematic diagram with the circuit elements represented by their symbols. The circuit shown in Figs. 8.1a and b is said to be incomplete because switch S is open; that is, it does not electrically connect the wire attached to it. When the switch is closed, electrically connecting those wires, the circuit is complete and charge can then flow through the switch and the wires. The charge that can flow through a conductor, such as a wire, is that of electrons. When the circuit of Fig.8.1 is completed, electrons are driven through the wires by an electric field that the battery sets up in the wires. The field drives electrons from capacitor plate h to the positive terminal of the battery; thus plate h becomes positively charged. The field drives just as many electrons from the negative terminal of the battery to capacitor plate l; this plate l, gaining electrons, becomes negatively charged just as much as plate h becomes positively charged. The potential difference between the initially uncharged plates is zero. As the plates
3 56 CHAPTER 8. CAPACITORS become oppositely charged, that potential difference increases until it equals the potential difference V between the terminals of the battery. Then plate h and the positive terminal of the battery are at the same potential, and there is no longer an electric field in the wire between them. Similarly, plate l and the negative terminal reach the same potential and there is then no electric fied in the wire between them. Thus, with the field zero, there is no further drive of electrons. The capacitor is said to be fully charged, with a potential difference V and a charge Q, which are related by Equ Q = CV (8.1) Note: Q is the magnitude of the charge on one plate of the capacitor. C is the capacitance of a the capacitor and its value depends only on the geometry of the plates and not on their charge or potential difference. The capacitance is a measure of how much charge must be put on the plates to produce a certain potential difference between them: the greater the capacitance, the more charge is required. The SI unit of capacitance that follows from Equ. 8.1 is the coulomb per volt. This unit occurs so often that it is goven a special name, the farad (F). Capacitor Networks When there is a combination of capacitors in a circuit, we can sometimes replace that combination with an equivalent capacitor, that is, a single capacitor that has the same capacitance as the actual combination of capacitors. With such a replacement, we can simplify the circuit, affording easier solutions for unknown quantities of the circuit. Here we discuss two basic combinations of capacitors that allow such a replacement. Capacitors in Parallel Figure 8.2 shows three capacitors in parallel to a battery. They are connected in parallel because the terminals of the battery are effectively wired directly to the plates of each of the three capacitors. Because the battery maintains a potential difference V betwen its terminal, it applies the same potential difference V across each capacitor.
4 57 Figure 8.2: (a) Capacitors in parallel. Each is connected directly to the voltage source just as if it were all alone, and so the total capacitance in parallel is just the sum of the individual capacitances. (b) The equivalent capacitor has a large plate area and can therefore hold more charge than the individual capacitors. For the three capacitors we can write Q 1 = C 1 V, Q 2 = C 2 V, Q 3 = C 3 V, The total charge on the parallel combination is Q = Q 1 + Q 2 + Q 3 (8.2) Q = C 1 V +C 2 V +C 3 V (8.3)
5 58 CHAPTER 8. CAPACITORS Q = (C 1 +C 2 +C 3 )V (8.4) The equivalent capacitance C eq, with the same total charge Q and applied potential difference V as the combination, is then C eq = Q V = C 1 +C 2 +C 3 (8.5) Capacitors in Series Figure 8.3 shows three capacitors connected in series to a battery, which maintains a potential difference V across the left and right terminals of the series combination. This arrangement produces potential differences V 1, V 2, and V 3 across capacitors C 1, C 2, and C 3, respectively, such that V 1 +V 2 +V 3 = V. We seek the single capacitance C eq that is equivalent to this series combination and thus can replace the combination. When the battery is connected, each capacitor must have the same charge Q. This is true even though the three capacitors may be of different types and may have different capacitances. The potential difference across each capacitor: V 1 = Q C 1 (8.6) V 2 = Q C 2 (8.7) V 3 = Q C 3 (8.8) The potential difference across the entire series combination is then V = V 1 +V 2 +V 3 (8.9)
6 59 Figure 8.3: (a) Capacitors connected in series. The magnitude of the charge on each plate is Q. (b) The equivalent capacitor has a larger plate separation d. Series connections produce a total capacitance that is less than that of any of the individual capacitors. V = Q C 1 + Q C 2 + Q C 3 (8.10) The equivalent capacitance C eq, is then ( 1 V = Q ) C 1 C 2 C 3 (8.11) C eq = Q V = 1 ( 1C1 + 1 C2 + 1 C3 ) (8.12) 1 C eq = 1 C C C 3 (8.13)
7 60 CHAPTER 8. CAPACITORS Storing Energy in an Electric Field Once the charging of a capacitor has begun, the addition of electrons to the negative plate involves doing work against the repulsive forces of the electrons which are already there. Equally, the removal of electrons from the positive plate requires that work is done against the attractive forces of the positive charges on that plate. The work which is done is stored in the form of electrical potential energy. where W = the energy stored by a charged capacitor (J) Q = the charge on the plates (C) V = the PD across the plates (V ) C = the capacitance (F) W = Q2 2C = 1 2 CV 2 = 1 QV (8.14) 2 Figure 8.4: Energy stored in the large capacitor is used to preserve the memory of an electronic calculator when its batteries are charged. The Medical Defibrillator The ability of a capacitor to store potential energy is the basic of defibrillator devices, which are used by emergency medical teams to stop the fibrillation of heart attack victims. In the portable version, a battery charges a capacitor to a high potential difference, storing a large amount of energy in less than a minute. The battery maintains only a modest potential
8 61 difference; an electronic circuit repeatedly uses that potential difference to greatly increase the potential difference of the capacitor. The power, or rate of energy transfer, during this process is also modest. Conducting leads ( paddles ) are placed on the victim s chest. When a control switch is closed, the capacitor sends a portion of its stored energy from paddle to paddle through the victim. As an example, when a 70µF capacitor in a defibrillator is charged to 5000V, the energy stored in the capacitor W = 1 2 CV 2 = 1 2 ( ) ( ) = 875J (8.15) About 200J of this energy is sent through the victim during a pulse of about 2.0ms. The power of the pulse is P = W t which is much greater than the power of the battery itself. = 200 = 100kW (8.16) Figure 8.5: Automated external defibrillators are found in many public places. These portable units provide verbal instructions for use in the important first few minutes for a person suffering a cardiac attack.
9 62 CHAPTER 8. CAPACITORS Joining two charged capacitors Fig. 8.6 shows two charged capacitors whose capacitances are C 1 and C 2. On closing S, charge flows until the potential difference across each capacitor is the same. The final charge, potential difference and energy of each capacitor can be calculated by making use of: (i) there is no change in the total amount of charge, (ii) the two capacitors acquire the same potential difference, (iii) the capacitors are in parallel and therefore the capacitance, C, of the combination is given by C = C 1 +C 2. Figure 8.6: Joining two charged capacitors. It turns out that unless the intial potential differences of the capacitors are the same, the total energy stored by the capacitors decreases when they are joined together. Energy is dissipated as heat in the connecting wire when charge flows from one capacitor to the other, and this accounts for the decrease in stored energy. Charging and Discharging a Capacitor through a resistor Many electronic circuits involve capacitors charging or discharging through resistors. When you use a flash camera, it takes a few seconds to charge the capacitor that powers the flash. The light flash discharges the capacitor in a tiny fraction of a second. Why does charging take longer than discharging?
10 63 Charge In the circuit of Fig. 8.7, when the switch is in position 1, the capacitor of capacitance C charges through the resistor of resistance R from a 9V battery. The microammeter records the charging current I and the voltmeter reads the PD V c across the capacitor at different times t. Figure 8.7: Position 1: Charging, Position 2: Discharging. If readings of I and V c are taken at 10 second intervals and graphs of these quantities plotted against t, Fig. 8.8a and b, they show that Figure 8.8: (a) I vs t, (b) V vs t. 1. I has its maximum value at the start when the capacitor begins to charge and then decreases more and more slowly until it becomes zero.
11 64 CHAPTER 8. CAPACITORS 2. V c rises rapidly from zero and slowly approaches its maximum value (9V) which it reaches when the capacitor is fully charged and I = 0. If the readings of the PD V R across the resistor were also taken, a graph of V R against t would have the same shape as that of I against t (since V R = IR at all times) and is shown as the dashed graph in Fig. 8.8b. All three graphs are exponential curves; those of I and V R are decay curves and that of V c is a growth curve. A graph of the charge on the capacitor Q against t has the same shape as the V c against t graph since Q = V c C. V c = V 0 (1 e t/rc) (8.17) Q c = Q 0 (1 e t/rc) (8.18) I = I 0 (e t/rc) (8.19) Also note that during charging the sum of the voltages across the resistor and capacitor equals the battery voltage V, that is V = V c +V R. Initially V C = 0, so V = V R. Finally, when the capacitor is fully charged, I = 0, therefore V R = 0 and V C = V. Time constant If the charging current I remained steady at its starting value, a capacitor would be fully charged after time T = C R seconds which, for the circuit of Fig. 8.7, equals = 50s. In fact I decreases with time, as Fig. 8.8a shows, and the capacitor has only 0.63 of its full charge and PD after 50s. Nevertheless, T = CR, called the time constant, is a useful measure of how long it takes a capacitor to charge through a resistor. The greater the values of C and R, the greater is T and the more slowly the PD across it rises. In general, T = CR is the time for V C (and Q) to rise to 63% of the charging PD at the start of the time, V.
12 65 Discharge In Fig. 8.7, when the switch is moved from position 1 to position 2, the capacitor discharges through the resistor. If the graphs of I, V C and V R are plotted as before, they are again exponential curves, as shown in Figs 8.9a and b. Note that: 1. The discharge current I, and so also V R, are in the opposite direction to that during charge. 2. V C and V R are in opposition during discharge. Figure 8.9: (a) I vs t, (b) V vs t. Using calculus it can be shown that V C decays according to the equation V C = V 0 e t/cr (8.20) where V 0 is the PD across the capacitor initially and e, the base of natural logarithms, equal 2.7. Substituting t = T = CR we get V C = V 0 e = V = 0.37V 0 (8.21)
13 66 CHAPTER 8. CAPACITORS In this case the time constant T is the time for V C to fall to 37% of its value at the start of the discharge. Also, Q C = Q 0 e t/cr (8.22) CR is known as the time constant of the circuit and is the time taken for the charge on the capacitor to fall to 1/e (i.e. 36.8%) of its initial value. Since V C = V R, i.e. the PD across the capacitor is equal and opposite to that across the resistor. V R = V 0 e t/cr (8.23) I = (V 0 /R)e t/cr = (Q 0 /CR)e t/cr (8.24) i.e. the current during discharge decreases exponentially. When doing calculations the minus sign in Equ can be ignored; it merely means that the capacitor s charge Q is decreasing. Figure 8.10: This stopmotion photograph of a hummingbird feeding on a flower was obtained with an extremely brief and intense flash of light powered by the discharge of a capacitor through a gas. Now we can explain why the flash camera in our scenario takes so much longer to charge than discharge; the resistance while charging is significantly greater than while discharging. The internal resistance of the battery accounts for most of the resistance while charging. As the battery ages, the increasing internal resistance makes the charging process even slower.
[1] (b) Fig. 1.1 shows a circuit consisting of a resistor and a capacitor of capacitance 4.5 μf. Fig. 1.1
1 (a) Define capacitance..... [1] (b) Fig. 1.1 shows a circuit consisting of a resistor and a capacitor of capacitance 4.5 μf. S 1 S 2 6.3 V 4.5 μf Fig. 1.1 Switch S 1 is closed and switch S 2 is left
More informationPhysicsAndMathsTutor.com 1
PhysicsAndMathsTutor.com 1 Q1. A 400 μf capacitor is charged so that the voltage across its plates rises at a constant rate from 0 V to 4.0 V in 20 s. What current is being used to charge the capacitor?
More informationChapter 2: Capacitor And Dielectrics
hapter 2: apacitor And Dielectrics In this chapter, we are going to discuss the different ways that a capacitor could be arranged in a circuit and how its capacitance could be increased. Overview apacitor
More informationOn the axes of Fig. 4.1, carefully sketch a graph to show how the potential difference V across the capacitor varies with time t. Label this graph L.
1 (a) A charged capacitor is connected across the ends of a negative temperature coefficient (NTC) thermistor kept at a fixed temperature. The capacitor discharges through the thermistor. The potential
More informationCAPACITORS / ENERGY STORED BY CAPACITORS / CHARGING AND DISCHARGING
PHYSICS A2 UNIT 4 SECTION 3: CAPACITANCE CAPACITORS / ENERGY STORED BY CAPACITORS / CHARGING AND DISCHARGING # Question CAPACITORS 1 What is current? Current is the rate of flow of charge in a circuit
More informationCapacitors. Example 1
Physics 30AP Resistors and apacitors I apacitors A capacitor is a device for storing electrical charge that consists of two conducting objects placed near one another but not touching. A A typical capacitor
More informationChapter 28. Direct Current Circuits
Chapter 28 Direct Current Circuits Circuit Analysis Simple electric circuits may contain batteries, resistors, and capacitors in various combinations. For some circuits, analysis may consist of combining
More informationName: Lab Partner: Section:
Chapter 6 Capacitors and RC Circuits Name: Lab Partner: Section: 6.1 Purpose The purpose of this experiment is to investigate the physics of capacitors in circuits. The charging and discharging of a capacitor
More informationAP Physics C. Electric Circuits III.C
AP Physics C Electric Circuits III.C III.C.1 Current, Resistance and Power The direction of conventional current Suppose the crosssectional area of the conductor changes. If a conductor has no current,
More informationENERGY AND TIME CONSTANTS IN RC CIRCUITS By: Iwana Loveu Student No Lab Section: 0003 Date: February 8, 2004
ENERGY AND TIME CONSTANTS IN RC CIRCUITS By: Iwana Loveu Student No. 416 614 5543 Lab Section: 0003 Date: February 8, 2004 Abstract: Two charged conductors consisting of equal and opposite charges forms
More informationUNIT G485 Module Capacitors PRACTICE QUESTIONS (4)
UNIT G485 Module 2 5.2.1 Capacitors PRACTICE QUESTIONS (4) 1 A 2200 µf capacitor is charged to a p.d. of 9.0 V and then discharged through a 100 kω resistor. (a) Calculate : (i) The initial charge stored
More informationParallel Plate Capacitor, cont. Parallel Plate Capacitor, final. Capacitance Isolated Sphere. Capacitance Parallel Plates, cont.
Chapter 6 Capacitance and Dielectrics Capacitors! Capacitors are devices that store electric charge! Examples of where capacitors are used include:! radio receivers (tune frequency)! filters in power supplies!
More informationChapter 6. Answers to examinationstyle questions. Answers Marks Examiner s tips
(a) Taking natural logs on both sides of V = V o e t/c gives ln V = ln V o + ln (e t/cr ) As ln (e t/cr ) = t CR then ln V = ln V o t CR = a bt hence a = ln V o and b = CR (b) (i) t/s 20 240 270 300 mean.427.233.033
More informationChapter 26. Capacitance and Dielectrics
Chapter 26 Capacitance and Dielectrics Capacitors Capacitors are devices that store electric charge Examples of where capacitors are used include: radio receivers filters in power supplies to eliminate
More informationFigure 1. (a) An alternating current power supply provides a current that keeps switching direction.
1 Figure 1 shows the output from the terminals of a power supply labelled d.c. (direct current). Voltage / V 6 4 2 0 2 0 5 10 15 20 25 Time/ms 30 35 40 45 50 Figure 1 (a) An alternating current power supply
More informationECE2262 Electric Circuits. Chapter 6: Capacitance and Inductance
ECE2262 Electric Circuits Chapter 6: Capacitance and Inductance Capacitors Inductors Capacitor and Inductor Combinations 1 CAPACITANCE AND INDUCTANCE Introduces two passive, energy storing devices: Capacitors
More informationChapter 16. Electric Energy and Capacitance
Chapter 16 Electric Energy and Capacitance Electric Potential Energy The electrostatic force is a conservative force It is possible to define an electrical potential energy function with this force Work
More informationECE2262 Electric Circuits. Chapter 6: Capacitance and Inductance
ECE2262 Electric Circuits Chapter 6: Capacitance and Inductance Capacitors Inductors Capacitor and Inductor Combinations OpAmp Integrator and OpAmp Differentiator 1 CAPACITANCE AND INDUCTANCE Introduces
More informationPH2200 Practice Exam II Summer 2003
PH00 Practice Exam II Summer 00 INSTRUCTIONS. Write your name and student identification number on the answer sheet and mark your recitation section.. Please cover your answer sheet at all times.. This
More information2005 AP PHYSICS C: ELECTRICITY AND MAGNETISM FREERESPONSE QUESTIONS
2005 AP PHYSICS C: ELECTRICITY AND MAGNETISM In the circuit shown above, resistors 1 and 2 of resistance R 1 and R 2, respectively, and an inductor of inductance L are connected to a battery of emf e and
More informationLab 10: DC RC circuits
Name: Lab 10: DC RC circuits Group Members: Date: TA s Name: Objectives: 1. To understand current and voltage characteristics of a DC RC circuit 2. To understand the effect of the RC time constant Apparatus:
More informationChapter 26. Capacitance and Dielectrics
Chapter 26 Capacitance and Dielectrics Capacitors Capacitors are devices that store electric charge Examples of where capacitors are used include: radio receivers filters in power supplies energystoring
More informationClass 6. Capacitance and Capacitors. Physics 106. Winter Press CTRLL to view as a slide show. Class 6. Physics 106.
and in and Energy Winter 2018 Press CTRLL to view as a slide show. From last time: The field lines are related to the field as follows: What is the electric potential? How are the electric field and the
More informationCoulomb s constant k = 9x10 9 N m 2 /C 2
1 Part 2: Electric Potential 2.1: Potential (Voltage) & Potential Energy q 2 Potential Energy of Point Charges Symbol U mks units [Joules = J] q 1 r Two point charges share an electric potential energy
More informationIntermediate Physics PHYS102
Intermediate Physics PHYS102 Dr Richard H. Cyburt Assistant Professor of Physics My office: 402c in the Science Building My phone: (304) 3846006 My email: rcyburt@concord.edu My webpage: www.concord.edu/rcyburt
More informationLab 08 Capacitors 2. Figure 2 Series RC circuit with SPDT switch to charge and discharge capacitor.
Lab 08: Capacitors Last edited March 5, 2018 Learning Objectives: 1. Understand the shortterm and longterm behavior of circuits containing capacitors. 2. Understand the mathematical relationship between
More informationChapter 27. Circuits
Chapter 27 Circuits 1 1. Pumping Chagres We need to establish a potential difference between the ends of a device to make charge carriers follow through the device. To generate a steady flow of charges,
More informationfirst name (print) last name (print) brock id (ab17cd) (lab date)
(ta initials) first name (print) last name (print) brock id (ab17cd) (lab date) Experiment 1 Capacitance In this Experiment you will learn the relationship between the voltage and charge stored on a capacitor;
More informationPHY222  Lab 7 RC Circuits: Charge Changing in Time Observing the way capacitors in RC circuits charge and discharge.
PHY222 Lab 7 RC Circuits: Charge Changing in Time Observing the way capacitors in RC circuits charge and discharge. Print Your Name Print Your Partners' Names You will return this handout to the instructor
More informationAgenda for Today. Elements of Physics II. Capacitors Parallelplate. Charging of capacitors
Capacitors Parallelplate Physics 132: Lecture e 7 Elements of Physics II Charging of capacitors Agenda for Today Combinations of capacitors Energy stored in a capacitor Dielectrics in capacitors Physics
More informationChapter 2: Capacitors And Dielectrics
hapter 2: apacitors And Dielectrics 2.1 apacitance and capacitors in series and parallel L.O 2.1.1 Define capacitance and use capacitance apacitor is a device that is capable of storing electric charges
More informationChapter 26 DirectCurrent Circuits
Chapter 26 DirectCurrent Circuits 1 Resistors in Series and Parallel In this chapter we introduce the reduction of resistor networks into an equivalent resistor R eq. We also develop a method for analyzing
More informationPhysics 115. General Physics II. Session 24 Circuits Series and parallel R Meters Kirchoff s Rules
Physics 115 General Physics II Session 24 Circuits Series and parallel R Meters Kirchoff s Rules R. J. Wilkes Email: phy115a@u.washington.edu Home page: http://courses.washington.edu/phy115a/ 5/15/14 Phys
More informationCapacitance, Resistance, DC Circuits
This test covers capacitance, electrical current, resistance, emf, electrical power, Ohm s Law, Kirchhoff s Rules, and RC Circuits, with some problems requiring a knowledge of basic calculus. Part I. Multiple
More informationVersion 001 CIRCUITS holland (1290) 1
Version CIRCUITS holland (9) This printout should have questions Multiplechoice questions may continue on the next column or page find all choices before answering AP M 99 MC points The power dissipated
More informationChapter 26. Capacitance and Dielectrics
Chapter 26 Capacitance and Dielectrics Capacitors Capacitors are devices that store electric charge Examples of where capacitors are used include: radio receivers filters in power supplies to eliminate
More informationCapacitance and Dielectrics. Chapter 26 HW: P: 10,18,21,29,33,48, 51,53,54,68
Capacitance and Dielectrics Chapter 26 HW: P: 10,18,21,29,33,48, 51,53,54,68 Capacitors Capacitors are devices that store electric charge and energy Examples of where capacitors are used include: radio
More informationENGR 2405 Chapter 6. Capacitors And Inductors
ENGR 2405 Chapter 6 Capacitors And Inductors Overview This chapter will introduce two new linear circuit elements: The capacitor The inductor Unlike resistors, these elements do not dissipate energy They
More informationElectronics Capacitors
Electronics Capacitors Wilfrid Laurier University October 9, 2015 Capacitor an electronic device which consists of two conductive plates separated by an insulator Capacitor an electronic device which consists
More informationFig. 1 Fig. 2. Calculate the total capacitance of the capacitors. (i) when connected as in Fig. 1. capacitance =... µf
1. Fig.1 shows two capacitors, A of capacitance 2µF, and B of capacitance 4µF, connected in parallel. Fig. 2 shows them connected in series. A twoway switch S can connect the capacitors either to a d.c.
More informationChapter 26. Capacitance and Dielectrics
Chapter 26 Capacitance and Dielectrics Circuits and Circuit Elements Electric circuits are the basis for the vast majority of the devices used in society. Circuit elements can be connected with wires to
More informationTactics Box 23.1 Using Kirchhoff's Loop Law
PH203 Chapter 23 solutions Tactics Box 231 Using Kirchhoff's Loop Law Description: Knight/Jones/Field Tactics Box 231 Using Kirchhoff s loop law is illustrated Learning Goal: To practice Tactics Box 231
More informationChapter 16. Electric Energy and Capacitance
Chapter 16 Electric Energy and Capacitance Electric Potential of a Point Charge The point of zero electric potential is taken to be at an infinite distance from the charge The potential created by a point
More informationPhysics Electricity & Opcs Lecture 8 Chapter 24 sec Fall 2017 Semester Professor
Physics 24100 Electricity & Opcs Lecture 8 Chapter 24 sec. 12 Fall 2017 Semester Professor Kol@ck How Much Energy? V 1 V 2 Consider two conductors with electric potentials V 1 and V 2 We can always pick
More informationCLASS X ELECTRICITY
Conductor Insulator: Materia Materials through which electric current cannot pass are called insulators. Electric Circuit: A continuous a CLASS X ELECTRICITY als through which electric current can pass
More informationP114 University of Rochester NAME S. Manly Spring 2010
Exam 2 (March 23, 2010) Please read the problems carefully and answer them in the space provided. Write on the back of the page, if necessary. Show your work where indicated. Problem 1 ( 8 pts): In each
More informationThe RC Time Constant
The RC Time Constant Objectives When a directcurrent source of emf is suddenly placed in series with a capacitor and a resistor, there is current in the circuit for whatever time it takes to fully charge
More information7/06 Electric Fields and Energy
Part ASome standard electric field and potential configurations About this lab: Electric fields are created by electric charges and exert force on charges. Electric potential gives an alternative description.
More informationREVISED HIGHER PHYSICS REVISION BOOKLET ELECTRONS AND ENERGY
REVSED HGHER PHYSCS REVSON BOOKLET ELECTRONS AND ENERGY Kinross High School Monitoring and measuring a.c. Alternating current: Mains supply a.c.; batteries/cells supply d.c. Electrons moving back and forth,
More informationCapacitance Consolidation
Capacitance Consolidation Q1.An uncharged 4.7 nf capacitor is connected to a 1.5 V supply and becomes fully charged. How many electrons are transferred to the negative plate of the capacitor during this
More information1) Two lightbulbs, one rated 30 W at 120 V and another rated 40 W at 120 V, are arranged in two different circuits.
1) Two lightbulbs, one rated 30 W at 120 V and another rated 40 W at 120 V, are arranged in two different circuits. a. The two bulbs are first connected in parallel to a 120 V source. i. Determine the
More informationWhat happens when things change. Transient current and voltage relationships in a simple resistive circuit.
Module 4 AC Theory What happens when things change. What you'll learn in Module 4. 4.1 Resistors in DC Circuits Transient events in DC circuits. The difference between Ideal and Practical circuits Transient
More informationSwitch. R 5 V Capacitor. ower upply. Voltmete. Goals. Introduction
Switch Lab 6. Circuits ower upply Goals + + R 5 V Capacitor V To appreciate the capacitor as a charge storage device. To measure the voltage across a capacitor as it discharges through a resistor, and
More informationIntroduction to AC Circuits (Capacitors and Inductors)
Introduction to AC Circuits (Capacitors and Inductors) Amin Electronics and Electrical Communications Engineering Department (EECE) Cairo University elc.n102.eng@gmail.com http://scholar.cu.edu.eg/refky/
More informationChapter 24. Capacitance and Dielectrics Lecture 1. Dr. Armen Kocharian
Chapter 24 Capacitance and Dielectrics Lecture 1 Dr. Armen Kocharian Capacitors Capacitors are devices that store electric charge Examples of where capacitors are used include: radio receivers filters
More informationLook over. examples 1, 2, 3, 5, 6. Look over. Chapter 25 section 18. Chapter 19 section 5 Example 10, 11
PHYS Look over hapter 5 section 8 examples,, 3, 5, 6 PHYS Look over hapter 7 section 79 Examples 8, hapter 9 section 5 Example 0, Things to Know ) How to find the charge on a apacitor. ) How to find
More informationLecture Outline Chapter 21. Physics, 4 th Edition James S. Walker. Copyright 2010 Pearson Education, Inc.
Lecture Outline Chapter 21 Physics, 4 th Edition James S. Walker Chapter 21 Electric Current and Direct Current Circuits Units of Chapter 21 Electric Current Resistance and Ohm s Law Energy and Power
More informationthe electrical nature of matter is inherent in its atomic structure E & M atoms are made up of p+, n, and e the nucleus has p+ and n
Electric Forces and Fields E & M the electrical nature of matter is inherent in its atomic structure atoms are made up of p+, n, and e a.k.a Electricity and Magnetism the nucleus has p+ and n surrounding
More informationPotential from a distribution of charges = 1
Lecture 7 Potential from a distribution of charges V = 1 4 0 X Smooth distribution i q i r i V = 1 4 0 X i q i r i = 1 4 0 Z r dv Calculating the electric potential from a group of point charges is usually
More informationDEVIL PHYSICS THE BADDEST CLASS ON CAMPUS IB PHYSICS
DEVIL PHYSICS THE BADDEST CLASS ON CAMPUS IB PHYSICS LSN 3: CAPACITANCE Questions From Reading Activity? Essential Idea: Capacitors can be used to store electrical energy for later use. Nature Of Science:
More informationFigure 1: Capacitor circuit
Capacitors INTRODUCTION The basic function of a capacitor 1 is to store charge and thereby electrical energy. This energy can be retrieved at a later time for a variety of uses. Often, multiple capacitors
More informationPhysics Investigation 10 Teacher Manual
Physics Investigation 10 Teacher Manual Observation When a light bulb is connected to a number of charged capacitors, it lights up for different periods of time. Problem What does the rate of discharging
More informationSTATIC ELECTRICITY & CAPACITANCE: Solutions to higher level questions
STATIC ELECTRICITY & CAPACITANCE: Solutions to higher level questions 2015 Question 8 (i) Define electric field strength. E = force per unit charge (ii) Draw a labelled diagram of a gold leaf electroscope.
More informationSummary Notes ALTERNATING CURRENT AND VOLTAGE
HIGHER CIRCUIT THEORY Wheatstone Bridge Circuit Any method of measuring resistance using an ammeter or voltmeter necessarily involves some error unless the resistances of the meters themselves are taken
More informationObjects usually are charged up through the transfer of electrons from one object to the other.
1 Part 1: Electric Force Review of Vectors Review your vectors! You should know how to convert from polar form to component form and vice versa add and subtract vectors multiply vectors by scalars Find
More informationMasteringPhysics: Assignment Print View. Problem 30.50
Page 1 of 15 Assignment Display Mode: View Printable Answers phy260s08 homework 13 Due at 11:00pm on Wednesday, May 14, 2008 View Grading Details Problem 3050 Description: A 15cmlong nichrome wire is
More informationM. C. Escher: Waterfall. 18/9/2015 [tsl425 1/29]
M. C. Escher: Waterfall 18/9/2015 [tsl425 1/29] Direct Current Circuit Consider a wire with resistance R = ρl/a connected to a battery. Resistor rule: In the direction of I across a resistor with resistance
More informationChapter 25. Capacitance
Chapter 25 Capacitance 25.2: Capacitance: 25.2: Capacitance: When a capacitor is charged, its plates have charges of equal magnitudes but opposite signs: q+ and q. However, we refer to the charge of a
More informationPhysics Module Form 5 Chapter 2 Electricity GCKL 2011 CHARGE AND ELECTRIC CURRENT
2.1 CHARGE AND ELECTRIC CURRENT Van de Graaf 1. What is a Van de Graaff generator? Fill in each of the boxes the name of the part shown. A device that produces and store electric charges at high voltage
More informationHow many electrons are transferred to the negative plate of the capacitor during this charging process? D (Total 1 mark)
Q1.n uncharged 4.7 nf capacitor is connected to a 1.5 V supply and becomes fully charged. How many electrons are transferred to the negative plate of the capacitor during this charging process? 2.2 10
More informationAssessment Schedule 2016 Physics: Demonstrate understanding electrical systems (91526)
NCEA evel 3 Physics (91526) 2016 page 1 of 5 Assessment Schedule 2016 Physics: Demonstrate understanding electrical systems (91526) Evidence Statement NØ N1 N 2 A 3 A 4 M 5 M 6 E 7 E 8 0 1A 2A 3A 4A or
More informationPhysics 2B Notes  Capacitors Spring 2018
Definition of a Capacitor Special Case: Parallel Plate Capacitor Capacitors in Series or Parallel Capacitor Network Definition of a Capacitor Webassign Chapter 0: 8, 9, 3, 4, 5 A capacitor is a device
More informationCAPACITANCE. Capacitor. Because of the effect of capacitance, an electrical circuit can store energy, even after being deenergized.
D ircuits APAITANE APAITANE Because of the effect of capacitance, an electrical circuit can store energy, even after being deenergized. EO 1.5 EO 1.6 EO 1.7 EO 1.8 EO 1.9 DESRIBE the construction of a
More informationSolutions to these tests are available online in some places (but not all explanations are good)...
The Physics GRE Sample test put out by ETS https://www.ets.org/s/gre/pdf/practice_book_physics.pdf OSU physics website has lots of tips, and 4 additional tests http://www.physics.ohiostate.edu/undergrad/ugs_gre.php
More informationSwitch. R 5 V Capacitor. ower upply. Voltmete. Goals. Introduction
Switch Lab 6. Circuits ower upply Goals + + R 5 V Capacitor V To appreciate the capacitor as a charge storage device. To measure the voltage across a capacitor as it discharges through a resistor, and
More informationCOPYRIGHTED MATERIAL. DC Review and PreTest. Current Flow CHAPTER
Kybett c0.tex V303/3/2008 8:44pm Page CHAPTER DC Review and PreTest Electronics cannot be studied without first understanding the basics of electricity. This chapter is a review and pretest on those
More informationChapter 19 Electric Potential and Electric Field
Chapter 19 Electric Potential and Electric Field The electrostatic force is a conservative force. Therefore, it is possible to define an electrical potential energy function with this force. Work done
More informationChapter 29. Electric Potential: Charged Conductor
hapter 29 Electric Potential: harged onductor 1 Electric Potential: harged onductor onsider two points (A and B) on the surface of the charged conductor E is always perpendicular to the displacement ds
More informationEXPERIMENT 5A RC Circuits
EXPERIMENT 5A Circuits Objectives 1) Observe and qualitatively describe the charging and discharging (decay) of the voltage on a capacitor. 2) Graphically determine the time constant for the decay, τ =.
More informationCapacitance. A capacitor consists of two conductors that are close but not touching. A capacitor has the ability to store electric charge.
Capacitance A capacitor consists of two conductors that are close but not touching. A capacitor has the ability to store electric charge. a) Parallelplate capacitor connected to battery. (b) is a circuit
More informationChapter 25 Current Resistance, and Electromotive Force
Chapter 25 Current Resistance, and Electromotive Force 1 Current In previous chapters we investigated the properties of charges at rest. In this chapter we want to investigate the properties of charges
More informationCapacitors and more. Lecture 9. Chapter 29. Physics II. Course website:
Lecture 9 Chapter 29 Physics II Capacitors and more Course website: http://faculty.uml.edu/andriy_danylov/teaching/physicsii Lecture Capture: http://echo360.uml.edu/danylov201415/physics2spring.html The
More informationCapacitors and more. Lecture 9. Chapter 29. Physics II. Course website:
Lecture 9 Chapter 29 Physics II Capacitors and more Course website: http://faculty.uml.edu/andriy_danylov/teaching/physicsii Lecture Capture: http://echo360.uml.edu/danylov201415/physics2spring.html The
More informationAC vs. DC Circuits. Constant voltage circuits. The voltage from an outlet is alternating voltage
Circuits AC vs. DC Circuits Constant voltage circuits Typically referred to as direct current or DC Computers, logic circuits, and battery operated devices are examples of DC circuits The voltage from
More informationPhysics 142 Steady Currents Page 1. Steady Currents
Physics 142 Steady Currents Page 1 Steady Currents If at first you don t succeed, try, try again. Then quit. No sense being a damn fool about it. W.C. Fields Electric current: the slow average drift of
More informationCapacitor investigations
Sensors: Loggers: Voltage Any EASYSENSE Capacitor investigations Logging time: EasyLog (20 s) Teacher s notes 01 Time constant for a capacitor  resistor circuit Theory The charging and discharging of
More informationCapacitors GOAL. EQUIPMENT. CapacitorDecay.cmbl 1. Building a Capacitor
PHYSICS EXPERIMENTS 133 Capacitor 1 Capacitors GOAL. To measure capacitance with a digital multimeter. To make a simple capacitor. To determine and/or apply the rules for finding the equivalent capacitance
More informationElectric Potential Energy Conservative Force
Electric Potential Energy Conservative Force Conservative force or field is a force field in which the total mechanical energy of an isolated system is conserved. Examples, Gravitation, Electrostatic,
More informationElectricity Mock Exam
Name: Class: _ Date: _ ID: A Electricity Mock Exam Multiple Choice Identify the letter of the choice that best completes the statement or answers the question.. What happens when a rubber rod is rubbed
More informationName Class Date. RC Circuit Lab
RC Circuit Lab Objectives: Students will be able to Use the ScienceWorkshop interface to investigate the relationship between the voltage remaining across a capacitor and the time taken for the discharge
More informationUniversity of TN Chattanooga Physics 1040L 8/18/2012 PHYSICS 1040L LAB LAB 4: R.C. TIME CONSTANT LAB
PHYSICS 1040L LAB LAB 4: R.C. TIME CONSTANT LAB OBJECT: To study the discharging of a capacitor and determine the time constant for a simple circuit. APPARATUS: Capacitor (about 24 μf), two resistors (about
More informationPhysics 2135 Exam 2 October 18, 2016
Exam Total / 200 Physics 2135 Exam 2 October 18, 2016 Printed Name: Rec. Sec. Letter: Five multiple choice questions, 8 points each. Choose the best or most nearly correct answer. 1. A light bulb having
More informationPHYS 2135 Exam II March 20, 2018
Exam Total /200 PHYS 2135 Exam II March 20, 2018 Name: Recitation Section: Five multiple choice questions, 8 points each. Choose the best or most nearly correct answer. For questions 69, solutions must
More informationPhys 2025, First Test. September 20, minutes Name:
Phys 05, First Test. September 0, 011 50 minutes Name: Show all work for maximum credit. Each problem is worth 10 points. Work 10 of the 11 problems. k = 9.0 x 10 9 N m / C ε 0 = 8.85 x 101 C / N m e
More informationChapter 7 DirectCurrent Circuits
Chapter 7 DirectCurrent Circuits 7. Introduction... 7. Electromotive Force... 7.3 Resistors in Series and in Parallel... 4 7.4 Kirchhoff s Circuit Rules... 6 7.5 VoltageCurrent Measurements... 8 7.6
More informationEXPERIMENT 07 TO STUDY DC RC CIRCUIT AND TRANSIENT PHENOMENA
EXPERIMENT 07 TO STUDY DC RC CIRCUIT AND TRANSIENT PHENOMENA DISCUSSION The capacitor is a element which stores electric energy by charging the charge on it. Bear in mind that the charge on a capacitor
More informationPhysics 219 Question 1 January
Lecture 616 Physics 219 Question 1 January 30. 2012. A (nonideal) battery of emf 1.5 V and internal resistance 5 Ω is connected to a light bulb of resistance 50 Ω. How much power is delivered to the
More informationElectricity and Magnetism. Capacitance
Electricity and Magnetism apacitance Sources of Electric Potential A potential difference can be created by moving charge from one conductor to another. The potential difference on a capacitor can produce
More informationExperiment 8: Capacitance and the Oscilloscope
Experiment 8: Capacitance and the Oscilloscope Nate Saffold nas2173@columbia.edu Office Hour: Mondays, 5:30PM6:30PM @ Pupin 1216 INTRO TO EXPERIMENTAL PHYSLAB 1493/1494/2699 Outline Capacitance: Capacitor
More informationElectromotive Force. The electromotive force (emf), ε, of a battery is the maximum possible voltage that the battery can provide between its terminals
Direct Current When the current in a circuit has a constant magnitude and direction, the current is called direct current Because the potential difference between the terminals of a battery is constant,
More information