Chapter 25 Current, Resistance, and Electromotive Force

Size: px
Start display at page:

Download "Chapter 25 Current, Resistance, and Electromotive Force"

Transcription

1 Chapter 25 Current, Resistance, and Electromotive Force Lecture by Dr. Hebin Li

2 Goals for Chapter 25 To understand current and how charges move in a conductor To understand resistivity and conductivity To calculate the resistance of a conductor To learn how an emf causes current in a circuit To calculate energy and power in circuits

3 Current Without electric field, free electrons move randomly in all directions. There is no net flow of charge in any direction. An electric field in a conductor causes charges to flow. A current is any motion of charge from one region to another. We define the current through a crosssection to be the net charge flowing through the area per unit time: I = dq dt The SI unit of current is the ampere (A). 1 A = 1 C/s

4 Direction of current flow A current can be produced by positive or negative charge flow. Conventional current is treated as a flow of positive charges. (We simply define it this way!) The moving charges in metals are electrons. The direction of electron flow is opposite to the direction of current!

5 Current, drift velocity, and current density Microscopic view of electric current: The net motion of an electron can be described by the drift velocity v d. Suppose there are n moving charged particles per unit volume and each particle has a charge q. The charge dq that flows our of the end of the cylinder during time dt is dq = q nav d dt = nqv d Adt So the current is I = dq dt = nqv da The current density is J = I A = nqv d I = dq dt = n q v da J = nqv d Current V.S. Current density

6 Resistivity The resistivity of a material is the ratio of the electric field in the material to the current density it causes: ρ = E J (definition of resistivity), unit: Ω m The conductivity is the reciprocal of the resistivity.

7 Example A 18-gauge copper wire has a cross-sectional area of m 2. It carries a current of 1.67 A. Find (a) the electric-field magnitude in the wire; (b) the potential difference between two points in the wire 50.0 m apart; (c) the resistance of a 50.0-m length of wire.

8 Example A copper wire has a square cross section 2.3 mm on a side. The wire is 4.0 m long and carries a current of 3.6 A. The density of free electrons is /m 3. Find the magnitude of (a) the current density in the wire and (b) the electric field in the wire. (c) how much time is required for an electron to travel the length of the wire?

9 Resistivity: there is more The resistivity is temperature dependent. Over a small temperature range, the resistivity of a metal can be represented approximately by the equation For other materials, the dependence can be different. For some materials, at a given temperature, ρ is constant and does not depend on E. Such a material is call an ohmic conductor or a linear conductor. For some materials, at a given temperature, ρ depends on E. Such a material is call an nonohmic conductor or a nonlinear conductor. (such as semiconductors)

10 Resistance Start with E = ρj Considering a wire with uniform cross-sectional area A and length L So we have, V = EL, I = JA V = ρi L A or V = ρl A I The resistance R is defined as the ratio of V to I R = V I

11 Example: A material of resistivity ρ is formed into a solid, truncated cone of height h and radii r 1 and r 2 at either end. (a)calculate the resistance of the cone between the two flat end surfaces. (b)what does the answer to (a) lead to when r 1 = r 2?

12 Electromotive force and circuits An electromotive force (emf) makes current flow. In spite of the name, an emf is not a force. It represents the energy per unit charge (like potential). It has a unit of V. The figures below show a source of emf in an open circuit (left) and in a complete circuit (right).

13 Internal resistance For an ideal emf source, the terminal voltage is V ab = E Real sources of emf actually contain some internal resistance r. The terminal voltage of an emf source is V ab = E Ir. For example, the terminal voltage of the 12-V battery shown at the right is less than 12 V when it is connected to the light bulb. The exact voltage depends on the current and internal resistance.

14 Symbols for circuit diagrams Table 25.4 shows the usual symbols used in circuit diagrams.

15 A source in an open circuit What are the readings on idealized voltmeter V and ammeter A? An idealized voltmeter has an infinitely large internal resistance. An idealized ammeter has a zero resistance. For an open circuit: I = 0, so The reading on A is zero. The reading on V is V ab = E Ir = E = 12 V

16 Source in a complete circuit What are the readings on V and A? The circuit is complete, the current in the circuit is I = E R+r = 12 V 4+2 Ω = 2 A The reading on A is 2 A. The reading on V is V ab = E Ir = 12 V 2 A 2 Ω = 8 V

17 Using voltmeters and ammeters

18 Potential changes around a circuit Follow the direction of the current, the potential increases by E going through an emf source. The potential decreases by IR going through a resistor. The net change in potential must be zero for a round trip in a circuit. E Ir IR = 0

19 Example: The circuit shown in the figure below contains two batteries, each with an emf and an internal resistance, and two resistors. Find (a)the current in the circuit (magnitude and direction). (b)the terminal voltage V ab of the 16.0-V battery. (c)the potential difference V ac of point a with respect to point c.

20 Energy and power in electric circuits The rate at which energy is delivered to (or extracted from) a circuit element is P = V ab I. The power delivered to a pure resistor is P = V ab I = I 2 R = V ab2 /R. Here we used I = V ab /R.

21 Power output of a source Consider the power output of a battery: The power delivered to the external circuit is P = V ab I The potential V ab = E Ir, plug it into the eqn. above P = E Ir I = EI I 2 r Net power output. Total power converted from chemical to electric energy. the power dissipated in battery.

22 Example: Power input and output In the following circuit, find (a) The rate of energy conversion from chemical to electrical energy. (b) The rate of energy dissipation in the battery. (c) The rate of energy dissipation in the 4-Ω resistor. (d) The battery s net power output.

Chapter 17. Current and Resistance. Sections: 1, 3, 4, 6, 7, 9

Chapter 17. Current and Resistance. Sections: 1, 3, 4, 6, 7, 9 Chapter 17 Current and Resistance Sections: 1, 3, 4, 6, 7, 9 Equations: 2 2 1 e r q q F = k 2 e o r Q k q F E = = I R V = A L R ρ = )] ( 1 [ o o T T + = α ρ ρ V I V t Q P = = R V R I P 2 2 ) ( = = C Q

More information

Flow Rate is the NET amount of water passing through a surface per unit time

Flow Rate is the NET amount of water passing through a surface per unit time Electric Current An Analogy Water Flow in a Pipe H 2 0 gallons/minute Flow Rate is the NET amount of water passing through a surface per unit time Individual molecules are bouncing around with speeds of

More information

Chapter 24: Electric Current

Chapter 24: Electric Current Chapter 24: Electric Current Electric current Electric current is a net flow of electric charge. Quantitatively, current is the rate at which charge crosses a given area. I = dq dt dq = q(n AL)=q(n Av

More information

Electric Current. Chapter 17. Electric Current, cont QUICK QUIZ Current and Resistance. Sections: 1, 3, 4, 6, 7, 9

Electric Current. Chapter 17. Electric Current, cont QUICK QUIZ Current and Resistance. Sections: 1, 3, 4, 6, 7, 9 Electric Current Chapter 17 Current and Resistance Sections: 1, 3, 4, 6, 7, 9 Whenever electric charges of like signs move, an electric current is said to exist The current is the rate at which the charge

More information

Electric Current. You must know the definition of current, and be able to use it in solving problems.

Electric Current. You must know the definition of current, and be able to use it in solving problems. Today s agenda: Electric Current. You must know the definition of current, and be able to use it in solving problems. Current Density. You must understand the difference between current and current density,

More information

Chapter 25: Electric Current

Chapter 25: Electric Current Chapter 25: Electric Current Conductors and Charge Carriers Consider a conducting piece of metal: The valence electrons are weakly bound to the nuclei form a fluidlike sea of electrons that can move through

More information

Chapter 25 Current Resistance, and Electromotive Force

Chapter 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 information

Current and Resistance

Current and Resistance Current and Resistance 1 Define the current. Understand the microscopic description of current. Discuss the rat at which the power transfer to a device in an electric current. 2 2-1 Electric current 2-2

More information

AP Physics C - E & M

AP Physics C - E & M Slide 1 / 27 Slide 2 / 27 AP Physics C - E & M Current, Resistance & Electromotive Force 2015-12-05 www.njctl.org Slide 3 / 27 Electric Current Electric Current is defined as the movement of charge from

More information

Chapter 27. Current And Resistance

Chapter 27. Current And Resistance Chapter 27 Current And Resistance Electric Current Electric current is the rate of flow of charge through some region of space The SI unit of current is the ampere (A) 1 A = 1 C / s The symbol for electric

More information

Physics 1214 Chapter 19: Current, Resistance, and Direct-Current Circuits

Physics 1214 Chapter 19: Current, Resistance, and Direct-Current Circuits Physics 1214 Chapter 19: Current, Resistance, and Direct-Current Circuits 1 Current current: (also called electric current) is an motion of charge from one region of a conductor to another. Current When

More information

CHAPTER 1 ELECTRICITY

CHAPTER 1 ELECTRICITY CHAPTER 1 ELECTRICITY Electric Current: The amount of charge flowing through a particular area in unit time. In other words, it is the rate of flow of electric charges. Electric Circuit: Electric circuit

More information

Physics 142 Steady Currents Page 1. Steady Currents

Physics 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 information

Electric Currents & Resistance

Electric Currents & Resistance Electric Currents & Resistance Electric Battery A battery produces electricity by transforming chemical energy into electrical energy. The simplest battery contains two plates or rods made of dissimilar

More information

Chapter 24: Electric Current

Chapter 24: Electric Current Chapter 24: Electric Current Current Definition of current A current is any motion of charge from one region to another. Suppose a group of charges move perpendicular to surface of area A. The current

More information

Chapters 24/25: Current, Circuits & Ohm s law Thursday September 29 th **Register your iclickers**

Chapters 24/25: Current, Circuits & Ohm s law Thursday September 29 th **Register your iclickers** Chapters 24/25: Current, Circuits & Ohm s law Thursday September 29 th **Register your iclickers** Conductors under dynamic conditions Current, current density, drift velocity Ohm s law Types of conductor

More information

Electric Currents. Resistors (Chapters 27-28)

Electric Currents. Resistors (Chapters 27-28) Electric Currents. Resistors (Chapters 27-28) Electric current I Resistance R and resistors Relation between current and resistance: Ohm s Law Resistivity ρ Energy dissipated by current. Electric power

More information

Chapter 16. Current and Drift Speed. Electric Current, cont. Current and Drift Speed, cont. Current and Drift Speed, final

Chapter 16. Current and Drift Speed. Electric Current, cont. Current and Drift Speed, cont. Current and Drift Speed, final Chapter 6 Current, esistance, and Direct Current Circuits Electric Current Whenever electric charges of like signs move, an electric current is said to exist The current is the rate at which the charge

More information

Chapter 27. Current and Resistance

Chapter 27. Current and Resistance Chapter 27 Current and Resistance Electric Current Most practical applications of electricity deal with electric currents. The electric charges move through some region of space. The resistor is a new

More information

Chapter 3: Electric Current and Direct-Current Circuit

Chapter 3: Electric Current and Direct-Current Circuit Chapter 3: Electric Current and Direct-Current Circuit n this chapter, we are going to discuss both the microscopic aspect and macroscopic aspect of electric current. Direct-current is current that flows

More information

Direct Current Circuits. February 18, 2014 Physics for Scientists & Engineers 2, Chapter 26 1

Direct Current Circuits. February 18, 2014 Physics for Scientists & Engineers 2, Chapter 26 1 Direct Current Circuits February 18, 2014 Physics for Scientists & Engineers 2, Chapter 26 1 Kirchhoff s Junction Rule! The sum of the currents entering a junction must equal the sum of the currents leaving

More information

Chapter 3: Electric Current And Direct-Current Circuits

Chapter 3: Electric Current And Direct-Current Circuits Chapter 3: Electric Current And Direct-Current Circuits 3.1 Electric Conduction 3.1.1 Describe the microscopic model of current Mechanism of Electric Conduction in Metals Before applying electric field

More information

9/22/16 ANNOUNCEMENT ANNOUNCEMENT FINAL EXAM

9/22/16 ANNOUNCEMENT ANNOUNCEMENT FINAL EXAM ANNOUNCEMENT Exam 1: Tuesday September 27, 2016, 8 PM 10 PM Location: Elliot Hall of Music Covers all readings, lectures, homework from Chapters 21 through 23 Multiple choice (1518 questions) Practice

More information

Handout 5: Current and resistance. Electric current and current density

Handout 5: Current and resistance. Electric current and current density 1 Handout 5: Current and resistance Electric current and current density Figure 1 shows a flow of positive charge. Electric current is caused by the flow of electric charge and is defined to be equal to

More information

Chapter 26 & 27. Electric Current and Direct- Current Circuits

Chapter 26 & 27. Electric Current and Direct- Current Circuits Chapter 26 & 27 Electric Current and Direct- Current Circuits Electric Current and Direct- Current Circuits Current and Motion of Charges Resistance and Ohm s Law Energy in Electric Circuits Combination

More information

Chapter 27. Current and Resistance

Chapter 27. Current and Resistance Chapter 27 Current and Resistance Electric Current Most practical applications of electricity deal with electric currents. The electric charges move through some region of space. The resistor is a new

More information

Chapter 18. Direct Current Circuits

Chapter 18. Direct Current Circuits Chapter 18 Direct Current Circuits Sources of emf The source that maintains the current in a closed circuit is called a source of emf Any devices that increase the potential energy of charges circulating

More information

Chapter 27 Current and resistance

Chapter 27 Current and resistance 27.1 Electric Current Chapter 27 Current and resistance 27.2 Resistance 27.3 A Model for Electrical Conduction 27.4 Resistance and Temperature 27.6 Electrical Power 2 27.1 Electric Current Consider a system

More information

Physics for Scientists & Engineers 2

Physics for Scientists & Engineers 2 Review The resistance R of a device is given by Physics for Scientists & Engineers 2 Spring Semester 2005 Lecture 8 R =! L A ρ is resistivity of the material from which the device is constructed L is the

More information

Electric currents (primarily, in metals)

Electric currents (primarily, in metals) Electric currents (primarily, in metals) Benjamin Franklin was experimenting electricity in the mid- XVIII Century. Nobody knew if it was the positive charges or negative charges carrying the current through

More information

and in a simple circuit Part 2

and in a simple circuit Part 2 Current, Resistance, and Voltage in a simple circuit Part 2 Electric Current Whenever electric charges of like signs move, an electric current is said to exist. Look at the charges flowing perpendicularly

More information

EXPERIMENT 12 OHM S LAW

EXPERIMENT 12 OHM S LAW EXPERIMENT 12 OHM S LAW INTRODUCTION: We will study electricity as a flow of electric charge, sometimes making analogies to the flow of water through a pipe. In order for electric charge to flow a complete

More information

XII PHYSICS [CURRENT ELECTRICITY] CHAPTER NO. 13 LECTURER PHYSICS, AKHSS, K.

XII PHYSICS [CURRENT ELECTRICITY] CHAPTER NO. 13 LECTURER PHYSICS, AKHSS, K. XII PHYSICS LECTURER PHYSICS, AKHSS, K affan_414@live.com https://promotephysics.wordpress.com [CURRENT ELECTRICITY] CHAPTER NO. 13 CURRENT Strength of current in a conductor is defined as, Number of coulombs

More information

Announcements. final exam average (excluding regrades): 79% regrade requests are due by Thursday, Sept 28 in recitation

Announcements. final exam average (excluding regrades): 79% regrade requests are due by Thursday, Sept 28 in recitation Announcements final exam average (excluding regrades): 79% ill file. regrade requests are due by Thursday, Sept 28 in recitation On a separate sheet of paper, explain the reason for your request. This

More information

Let s go to something more concrete

Let s go to something more concrete Let s go to something more concrete Let me define an electric current Whenever charges of like sign are moving, an electric current exists Suppose I have a surface A with charges (assume + because of Franklin

More information

Chapter 25 Electric Currents and. Copyright 2009 Pearson Education, Inc.

Chapter 25 Electric Currents and. Copyright 2009 Pearson Education, Inc. Chapter 25 Electric Currents and Resistance 25-1 The Electric Battery Volta discovered that electricity could be created if dissimilar metals were connected by a conductive solution called an electrolyte.

More information

Chapter 27. Current And Resistance

Chapter 27. Current And Resistance Chapter 27 Current And Resistance Electric Current Electric current is the rate of flow of charge through some region of space The SI unit of current is the ampere (A) 1 A = 1 C / s The symbol for electric

More information

Capacitance. A different kind of capacitor: Work must be done to charge a capacitor. Capacitors in circuits. Capacitor connected to a battery

Capacitance. A different kind of capacitor: Work must be done to charge a capacitor. Capacitors in circuits. Capacitor connected to a battery Capacitance The ratio C = Q/V is a conductor s self capacitance Units of capacitance: Coulomb/Volt = Farad A capacitor is made of two conductors with equal but opposite charge Capacitance depends on shape

More information

Electric Current. Electric current is the rate of flow of charge through some region of space The SI unit of current is the ampere (A)

Electric Current. Electric current is the rate of flow of charge through some region of space The SI unit of current is the ampere (A) Electric Current Electric current is the rate of flow of charge through some region of space The SI unit of current is the ampere (A) 1 A = 1 C / s The symbol for electric current is I Average Electric

More information

2/25/2014. Circuits. Properties of a Current. Conservation of Current. Definition of a Current A. I A > I B > I C B. I B > I A C. I C D. I A E.

2/25/2014. Circuits. Properties of a Current. Conservation of Current. Definition of a Current A. I A > I B > I C B. I B > I A C. I C D. I A E. Circuits Topics: Current Conservation of current Batteries Resistance and resistivity Simple circuits 0.1 Electromotive Force and Current Conventional current is the hypothetical flow of positive charges

More information

Chapter 2. Engr228 Circuit Analysis. Dr Curtis Nelson

Chapter 2. Engr228 Circuit Analysis. Dr Curtis Nelson Chapter 2 Engr228 Circuit Analysis Dr Curtis Nelson Chapter 2 Objectives Understand symbols and behavior of the following circuit elements: Independent voltage and current sources; Dependent voltage and

More information

AP Physics C. Electric Circuits III.C

AP 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 cross-sectional area of the conductor changes. If a conductor has no current,

More information

Chapter 17 Electric Current and Resistance Pearson Education, Inc.c

Chapter 17 Electric Current and Resistance Pearson Education, Inc.c Chapter 17 Electric Current and Resistance 2010 Pearson Education, Inc.c 1 Units of Chapter 17 Batteries and Direct Current Current and Drift Velocity Resistance and Ohm s Law Electric Power 2010 Pearson

More information

Electric Charge. Electric Charge ( q ) unbalanced charges positive and negative charges. n Units Coulombs (C)

Electric Charge. Electric Charge ( q ) unbalanced charges positive and negative charges. n Units Coulombs (C) Electric Charge Electric Charge ( q ) unbalanced charges positive and negative charges n Units Coulombs (C) Electric Charge How do objects become charged? Types of materials Conductors materials in which

More information

Applied Natural Sciences

Applied Natural Sciences Het basisvak Toegepaste Natuurwetenschappen http://www.phys.tue.nl/nfcmr/natuur/collegenatuur.html Applied Natural Sciences Leo Pel e mail: 3nab0@tue.nl http://tiny.cc/3nab0 Bijles Email: p.j.neuraij@tue.nl

More information

University Physics (PHY 2326)

University Physics (PHY 2326) Chapter 25 University Physics (PHY 2326) Lecture 7 Electrostatics and electrodynamics Capacitance and capacitors capacitors with dielectrics Electric current current and drift speed resistance and Ohm

More information

6. In a dry cell electrical energy is obtained due to the conversion of:

6. In a dry cell electrical energy is obtained due to the conversion of: 1. If a wire of uniform area of cross section is cut into two halves (equal in size), the resistivity of each part will be: a) Halved. b) Doubled. c) Becomes four times its initial value. d) Remains the

More information

SIMPLE D.C. CIRCUITS AND MEASUREMENTS Background

SIMPLE D.C. CIRCUITS AND MEASUREMENTS Background SIMPLE D.C. CICUITS AND MEASUEMENTSBackground This unit will discuss simple D.C. (direct current current in only one direction) circuits: The elements in them, the simple arrangements of these elements,

More information

Chapter 25 Electric Currents and Resistance. Copyright 2009 Pearson Education, Inc.

Chapter 25 Electric Currents and Resistance. Copyright 2009 Pearson Education, Inc. Chapter 25 Electric Currents and Resistance 25-4 Resistivity Example 25-5: Speaker wires. Suppose you want to connect your stereo to remote speakers. (a) If each wire must be 20 m long, what diameter copper

More information

Lecture 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. 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 information

Chapter 26 Direct-Current Circuits

Chapter 26 Direct-Current Circuits Chapter 26 Direct-Current 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 information

ELECTRIC CURRENT. Ions CHAPTER Electrons. ELECTRIC CURRENT and DIRECT-CURRENT CIRCUITS

ELECTRIC CURRENT. Ions CHAPTER Electrons. ELECTRIC CURRENT and DIRECT-CURRENT CIRCUITS LCTRC CURRNT CHAPTR 25 LCTRC CURRNT and DRCTCURRNT CRCUTS Current as the motion of charges The Ampère Resistance and Ohm s Law Ohmic and nonohmic materials lectrical energy and power ons lectrons nside

More information

Electric Current. Equilibrium: Nonequilibrium: Electric current: E = 0 inside conductor. Mobile charge carriers undergo random motion.

Electric Current. Equilibrium: Nonequilibrium: Electric current: E = 0 inside conductor. Mobile charge carriers undergo random motion. Electric Current Equilibrium: E = 0 inside conductor. Mobile charge carriers undergo random motion. Nonequilibrium: E 0 inside conductor. Mobile charge carriers undergo random motion and drift. Positive

More information

Question 3: How is the electric potential difference between the two points defined? State its S.I. unit.

Question 3: How is the electric potential difference between the two points defined? State its S.I. unit. EXERCISE (8 A) Question : Define the term current and state its S.I unit. Solution : Current is defined as the rate of flow of charge. I = Q/t Its S.I. unit is Ampere. Question 2: Define the term electric

More information

Closed loop of moving charges (electrons move - flow of negative charges; positive ions move - flow of positive charges. Nucleus not moving)

Closed loop of moving charges (electrons move - flow of negative charges; positive ions move - flow of positive charges. Nucleus not moving) Unit 2: Electricity and Magnetism Lesson 3: Simple Circuits Electric circuits transfer energy. Electrical energy is converted into light, heat, sound, mechanical work, etc. The byproduct of any circuit

More information

Electric Currents and Circuits

Electric Currents and Circuits Nicholas J. Giordano www.cengage.com/physics/giordano Chapter 19 Electric Currents and Circuits Marilyn Akins, PhD Broome Community College Electric Circuits The motion of charges leads to the idea of

More information

ELECTRIC CURRENTS D R M A R T A S T A S I A K D E P A R T M E N T O F C Y T O B I O L O G Y A N D P R O T E O M I C S

ELECTRIC CURRENTS D R M A R T A S T A S I A K D E P A R T M E N T O F C Y T O B I O L O G Y A N D P R O T E O M I C S ELECTRIC CURRENTS D R M A R T A S T A S I A K D E P A R T M E N T O F C Y T O B I O L O G Y A N D P R O T E O M I C S lecture based on 2016 Pearson Education, Ltd. The Electric Battery Electric Current

More information

Chapter 18 Electric Currents

Chapter 18 Electric Currents Chapter 18 Electric Currents 1 The Electric Battery Volta discovered that electricity could be created if dissimilar metals were connected by a conductive solution called an electrolyte. This is a simple

More information

5. ELECTRIC CURRENTS

5. ELECTRIC CURRENTS 5. ELECTRIC CURRENTS TOPIC OUTLINE Section Recommended Time Giancoli Section 5.1 Potential Difference, Current, Resistance 5.2 Electric Circuits 3h 19.1, 19.2 6.2 Electric Field and Force 6.3 Magnetic

More information

Chapter 25. Electromotive Force. PowerPoint Lectures for University Physics, Twelfth Edition Hugh D. Young and Roger A. Freedman

Chapter 25. Electromotive Force. PowerPoint Lectures for University Physics, Twelfth Edition Hugh D. Young and Roger A. Freedman Chapter 25 Current, Resistance, and Electromotive Force PowerPoint Lectures for University Physics, Twelfth Edition Hugh D. Young and Roger A. Freedman Lectures by James Pazun Main points (I, R, emf) 1.

More information

6 Chapter. Current and Resistance

6 Chapter. Current and Resistance 6 Chapter Current and Resistance 6.1 Electric Current... 6-2 6.1.1 Current Density... 6-2 6.2 Ohm s Law... 6-5 6.3 Summary... 6-8 6.4 Solved Problems... 6-9 6.4.1 Resistivity of a Cable... 6-9 6.4.2 Charge

More information

CLASS X- ELECTRICITY

CLASS 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 information

Version 001 CIRCUITS holland (1290) 1

Version 001 CIRCUITS holland (1290) 1 Version CIRCUITS holland (9) This print-out should have questions Multiple-choice questions may continue on the next column or page find all choices before answering AP M 99 MC points The power dissipated

More information

Direct Currents. We will now start to consider charges that are moving through a circuit, currents. Sunday, February 16, 2014

Direct Currents. We will now start to consider charges that are moving through a circuit, currents. Sunday, February 16, 2014 Direct Currents We will now start to consider charges that are moving through a circuit, currents. 1 Direct Current Current usually consists of mobile electrons traveling in conducting materials Direct

More information

Chapter 17. Current and Resistance

Chapter 17. Current and Resistance Chapter 17 Current and Resistance Electric Current The current is the rate at which the charge flows through a surface Look at the charges flowing perpendicularly through a surface of area A I av The SI

More information

Chapter 27: Current and Resistance

Chapter 27: Current and Resistance Chapter 7: Current and esistance In this section of the course we will be studying the flow of electric charge, current, in a circuit. We have already seen electric current when we first discussed electric

More information

fehmibardak.cbu.tr Temporary Office 348, Mühendislik Fakültesi B Blok

fehmibardak.cbu.tr Temporary Office 348, Mühendislik Fakültesi B Blok fehmibardak.cbu.tr Temporary Office 348, Mühendislik Fakültesi B Blok 1 Course Progress Introductory level Electrostatic, Coulomb s Law Electric Field, Gauss Law Magnetic field, Maxwell s Equations Current,

More information

Lecture #3. Review: Power

Lecture #3. Review: Power Lecture #3 OUTLINE Power calculations Circuit elements Voltage and current sources Electrical resistance (Ohm s law) Kirchhoff s laws Reading Chapter 2 Lecture 3, Slide 1 Review: Power If an element is

More information

ELECTRICITY. Electric Circuit. What do you already know about it? Do Smarty Demo 5/30/2010. Electric Current. Voltage? Resistance? Current?

ELECTRICITY. Electric Circuit. What do you already know about it? Do Smarty Demo 5/30/2010. Electric Current. Voltage? Resistance? Current? ELECTRICITY What do you already know about it? Voltage? Resistance? Current? Do Smarty Demo 1 Electric Circuit A path over which electrons travel, out through the negative terminal, through the conductor,

More information

10/14/2018. Current. Current. QuickCheck 30.3

10/14/2018. Current. Current. QuickCheck 30.3 Current If QCurrent is the total amount of charge that has moved past a point in a wire, we define the current I in the wire to be the rate of charge flow: The SI unit for current is the coulomb per second,

More information

Physics 201. Professor P. Q. Hung. 311B, Physics Building. Physics 201 p. 1/3

Physics 201. Professor P. Q. Hung. 311B, Physics Building. Physics 201 p. 1/3 Physics 201 p. 1/3 Physics 201 Professor P. Q. Hung 311B, Physics Building Physics 201 p. 2/3 Summary of last lecture Equipotential surfaces: Surfaces where the potential is the same everywhere, e.g. the

More information

Current. I = ei e = en e Av d. The current, which is Coulomb s per second, is simply

Current. I = ei e = en e Av d. The current, which is Coulomb s per second, is simply Current The current, which is Coulomb s per second, is simply I = ei e = en e Av d e is the charge is the electron! ne is the density of electrons! A is the cross sectional area of the wire! vd is the

More information

A free web support in Education. Internal resistance of the battery, r = 3 Ω. Maximum current drawn from the battery = I According to Ohm s law,

A free web support in Education. Internal resistance of the battery, r = 3 Ω. Maximum current drawn from the battery = I According to Ohm s law, Exercises Question 3.1: The storage battery of a car has an emf of 12 V. If the internal resistance of the battery is 0.4Ω, what is the maximum current that can be drawn from the battery? Answer 3.1: Emf

More information

Lecture 6. Previous Lecture. Capacitors C. Capacitors in series Capacitors in parallel E stored in an E field

Lecture 6. Previous Lecture. Capacitors C. Capacitors in series Capacitors in parallel E stored in an E field Lecture 6 Previous Lecture Q Capacitors C V Capacitors in series Capacitors in parallel E stored in an E field 1 1 = = C C Δ series parallel This Lecture Current Resistivity as a property of materials

More information

1. How does a light bulb work?

1. How does a light bulb work? AP Physics 1 Lesson 12.a Electric Current and Circuits Outcomes 1. Determine the resistance of a resistor given length, cross-sectional area and length. 2. Relate the movement of charge to differences

More information

Topic 5.2 Heating Effect of Electric Currents

Topic 5.2 Heating Effect of Electric Currents Topic 5.2 Heating Effect of Electric Currents Kari Eloranta 2017 Jyväskylän Lyseon lukio International Baccalaureate February 14, 2017 Topic 5.2 Heating Effect of Electric Currents In subtopic 5.2 we study

More information

Electric Current & DC Circuits

Electric Current & DC Circuits Electric Current & DC Circuits Circuits Click on the topic to go to that section Conductors Resistivity and Resistance Circuit Diagrams Measurement EMF & Terminal Voltage Kirchhoff's Rules Capacitors*

More information

Insulators Non-metals are very good insulators; their electrons are very tightly bonded and cannot move.

Insulators Non-metals are very good insulators; their electrons are very tightly bonded and cannot move. SESSION 11: ELECTRIC CIRCUITS Key Concepts Resistance and Ohm s laws Ohmic and non-ohmic conductors Series and parallel connection Energy in an electric circuit X-planation 1. CONDUCTORS AND INSULATORS

More information

ENGR 2405 Class No Electric Circuits I

ENGR 2405 Class No Electric Circuits I ENGR 2405 Class No. 48056 Electric Circuits I Dr. R. Williams Ph.D. rube.williams@hccs.edu Electric Circuit An electric circuit is an interconnec9on of electrical elements Charge Charge is an electrical

More information

CURRENT ELECTRICITY The charge flowing any cross-section per unit time in a conductor is called electric current.

CURRENT ELECTRICITY The charge flowing any cross-section per unit time in a conductor is called electric current. CUENT ELECTICITY Important Points:. Electric Current: The charge flowing any cross-section per unit time in a conductor is called electric current. Electric Current I q t. Current Density: a) The current

More information

Physics 11b Lecture #8

Physics 11b Lecture #8 Physics 11b Lecture #8 Current and Resistance S&J Chapter 27 Administravia First midterm this Thursday Covers up to and including capacitance Lectures #1 #7, textbook chapters 23 26 Five problems Problem

More information

Designing Information Devices and Systems I Fall 2018 Lecture Notes Note Resistive Touchscreen - expanding the model

Designing Information Devices and Systems I Fall 2018 Lecture Notes Note Resistive Touchscreen - expanding the model EECS 16A Designing Information Devices and Systems I Fall 2018 Lecture Notes Note 13 13.1 Resistive Touchscreen - expanding the model Recall the physical structure of the simple resistive touchscreen given

More information

1 Written and composed by: Prof. Muhammad Ali Malik (M. Phil. Physics), Govt. Degree College, Naushera

1 Written and composed by: Prof. Muhammad Ali Malik (M. Phil. Physics), Govt. Degree College, Naushera CURRENT ELECTRICITY Q # 1. What do you know about electric current? Ans. Electric Current The amount of electric charge that flows through a cross section of a conductor per unit time is known as electric

More information

AC vs. DC Circuits. Constant voltage circuits. The voltage from an outlet is alternating voltage

AC 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 information

Physics 2B: Review for Celebration #2. Chapter 22: Current and Resistance

Physics 2B: Review for Celebration #2. Chapter 22: Current and Resistance Physics 2: eview for Celebration #2 Chapter 22: Current and esistance Current: q Current: I [I] amps (A) 1 A 1 C/s t Current flows because a potential difference across a conductor creates an electric

More information

Chapter 26 Direct-Current Circuits

Chapter 26 Direct-Current Circuits Chapter 26 Direct-Current 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 information

Look over Chapter 26 sections 1-7 Examples 3, 7. Look over Chapter 18 sections 1-5, 8 over examples 1, 2, 5, 8, 9,

Look over Chapter 26 sections 1-7 Examples 3, 7. Look over Chapter 18 sections 1-5, 8 over examples 1, 2, 5, 8, 9, Look over Chapter 26 sections 1-7 Examples 3, 7 Look over Chapter 18 sections 1-5, 8 over examples 1, 2, 5, 8, 9, 1)How to find a current in a wire. 2)What the Current Density and Draft Speed are. 3)What

More information

Physics 7B-1 (A/B) Professor Cebra. Winter 2010 Lecture 2. Simple Circuits. Slide 1 of 20

Physics 7B-1 (A/B) Professor Cebra. Winter 2010 Lecture 2. Simple Circuits. Slide 1 of 20 Physics 7B-1 (A/B) Professor Cebra Winter 2010 Lecture 2 Simple Circuits Slide 1 of 20 Conservation of Energy Density In the First lecture, we started with energy conservation. We divided by volume (making

More information

Chapter 3: Current and Resistance. Direct Current Circuits

Chapter 3: Current and Resistance. Direct Current Circuits Chapter 3: Current and Resistance. Direct Current Circuits 3.1. Electric Current 3.2. Resistance and Resistivity 3.3. Ohm s Law and a Microscopic View of Ohm s Law 3.4. Semiconductors and Superconductors

More information

Chapter 27 Current and Resistance 27.1 Electric Current

Chapter 27 Current and Resistance 27.1 Electric Current Chapter 27 Current and esistance 27.1 Electric Current Electric current: dq dt, unit: ampere 1A = 1C s The rate at which charge flows through a surface. No longer have static equilibrium. E and Q can 0

More information

M. C. Escher: Waterfall. 18/9/2015 [tsl425 1/29]

M. 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 information

Chapter 27: Current & Resistance. HW For Chapter 27: 6, 18, 20, 30, 42, 48, 52, 56, 58, 62, 68

Chapter 27: Current & Resistance. HW For Chapter 27: 6, 18, 20, 30, 42, 48, 52, 56, 58, 62, 68 Chapter 27: Current & Resistance HW For Chapter 27: 6, 18, 20, 30, 42, 48, 52, 56, 58, 62, 68 Positive Charges move from HI to LOW potential. HI V LOW V Negative Charges move from LOW to HI potential.

More information

PHYS 1444 Section 002 Lecture #13

PHYS 1444 Section 002 Lecture #13 PHYS 1444 Section 002 Lecture #13 Monday, Oct. 16, 2017 Dr. Animesh Chatterjee (disguising as Dr. Yu) Chapter 25 Electric Current Ohm s Law: Resisters, Resistivity Electric Power Alternating Current Microscopic

More information

AP Physics C - E & M

AP Physics C - E & M AP Physics C - E & M Current and Circuits 2017-07-12 www.njctl.org Electric Current Resistance and Resistivity Electromotive Force (EMF) Energy and Power Resistors in Series and in Parallel Kirchoff's

More information

Capacitance, Resistance, DC Circuits

Capacitance, 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 information

Chapter 25 Electric Currents and Resistance. Copyright 2009 Pearson Education, Inc.

Chapter 25 Electric Currents and Resistance. Copyright 2009 Pearson Education, Inc. Chapter 25 Electric Currents and Resistance Units of Chapter 25 The Electric Battery Electric Current Ohm s Law: Resistance and Resistors Resistivity Electric Power Units of Chapter 25 Power in Household

More information

Direct Current (DC) Circuits

Direct Current (DC) Circuits Direct Current (DC) Circuits NOTE: There are short answer analysis questions in the Participation section the informal lab report. emember to include these answers in your lab notebook as they will be

More information

Physics 1302W.400 Lecture 21 Introductory Physics for Scientists and Engineering II

Physics 1302W.400 Lecture 21 Introductory Physics for Scientists and Engineering II Physics 1302W.400 Lecture 21 Introductory Physics for Scientists and Engineering II In today s lecture, we will learn to: Calculate the resistance of a conductor depending on the material and shape Apply

More information

SPH3U1 Lesson 01 Electricity

SPH3U1 Lesson 01 Electricity ELECTRIC CURRENT AND POTENTIAL DIFFERENCE LEARNING GOALS Students will: Define what is meant by electric current. Solve problems involving current, charge and time. Know the difference between electron

More information

LABORATORY 4 ELECTRIC CIRCUITS I. Objectives

LABORATORY 4 ELECTRIC CIRCUITS I. Objectives LABORATORY 4 ELECTRIC CIRCUITS I Objectives to be able to discuss potential difference and current in a circuit in terms of electric field, work per unit charge and motion of charges to understand that

More information