General Physics (PHY 2140)
|
|
- Justina Robertson
- 5 years ago
- Views:
Transcription
1 General Physics (PHY 2140) Lecture 4 Electrostatics and electrodynamics Capacitance and capacitors capacitors with dielectrics Electric current current and drift speed resistance and Ohm s law resistivity Last lecture: 1. Equipotential surfaces. Lightning Review They are defined as a surface in space on which the potential is the same for every point (surfaces of constant voltage) The electric field at every point of an equipotential surface is perpendicular to the surface Chapter Last lecture: 1. Capacitance and capacitors Combinations of capacitors Parallel Series Parallel-plate capacitor Energy stored in a capacitor Lightning Review Q C = Ceq = C1 C =... Ceq C1 C2 2 1 Q 1 U = QV = = CV C = ε0 d 2 2C 2 Review Problem: Consider an isolated simple parallel-plate capacitor whose plates are given equal and opposite charges and are separated by a distance d. Suppose the plates are pulled apart until they are separated by a distance D>d. The electrostatic energy stored in a capacitor is a. greater than b. the same as c. smaller than before the plates were pulled apart Capacitors with dielectrics dielectric is an insulating material (rubber, glass, etc.) Consider an insolated, charged capacitor Q Q Q V 0 V Notice that the potential difference decreases (κ = V 0 /V) Since charge stayed the same (Q=Q 0 ) capacitance increases C Q Q κq = = = = V V0 κ V0 dielectric constant: κ = C/C 0 Dielectric constant is a material property Q κc 0 nsert a dielectric 4 1
2 Capacitors with dielectrics - notes Capacitance is multiplied by a factor k when the dielectric fills the region between the plates completely E.g., for a parallel-plate plate capacitor C = κε 0 d The capacitance is limited from above by the electric discharge that can occur through the dielectric material separating the plates n other words, there exists a maximum of the electric field, sometimes called dielectric strength,, that can be produced in the dielectric before it breaks down Dielectric constants and dielectric strengths of various materials at room temperature Material Vacuum ir Water Fused quartz Dielectric constant, κ Dielectric strength (V/m) * For a more complete list, see Table 16.1 * For short duration (μsec) pulses 5 6 Example Take a parallel plate capacitor whose plates have an area of 2.0 m 2 and are separated by a distance of 1mm. The capacitor is charged to an initial voltage of 3 kv and then disconnected from the charging source. n insulating material is placed between the plates, completely filling the space, resulting in a decrease in the capacitors voltage to 1 kv. Determine the original and new capacitance, the charge on the capacitor, and the dielectric constant of the material. Take a parallel plate capacitor whose plates have an area of 2 m 2 and are separated by a distance of 1mm. The capacitor is charged to an initial voltage of 3 kv and then disconnected from the charging source. n insulating material is placed between the plates, completely filling the space, resulting in a decrease in the capacitors voltage to 1 kv. Determine the original and new capacitance, the charge on the capacitor, and the dielectric constant of the material. Given: 1 =3,000 V 2 =1,000 V = 2.00 m 2 d = 0.01 m Find: C =? C 0 =? Q =? κ =? Since we are dealing with the parallel-plate capacitor, the original capacitance can be found as m C0 = ε0 = ( C N m ) = 18 nf 3 d m The dielectric constant and the new capacitance are C = κc = C = 318 nf = 54nF The charge on the capacitor can be found to be ( )( ) 9 5 Q= C Δ V = F V = C
3 How does an insulating dielectric material reduce electric fields by producing effective surface charge densities? Reorientation of polar molecules nduced polarization of non-polar molecules 17.1 Electric Current Whenever charges of like signs move in a given direction, a current is said to exist. Consider charges are moving perpendicularly to a surface of area. Definition: the current is the rate at which charge flows through this surface. Dielectric Breakdown: breaking of molecular bonds/ionization of molecules Electric Current - Definition 17.1 Electric Current - Units Given an amount of charge, ΔQ,, passing through the area in a time interval Δt,, the current is the ratio of the charge to the time interval. ΔQ = Δ t The S units of current is the ampere (). 1 = 1 C/s 1 of current is equivalent to 1 C of charge passing through the area in a time interval of 1 s
4 17.1 Electric Current Remark 1 Currents may be carried by the motion of positive or negative charges. t is conventional to give the current the same direction as the flow of positive charge Electric Current Remark 2 n a metal conductor such as copper, the current is due to the motion of the electrons (negatively charged). The direction of the current in copper is thus opposite the direction of the electrons v Electric Current Remark Electric Current Remark 4 n a beam of protons at a particle accelerator (such as RHC at Brookhaven national laboratory), the current is the same direction as the motion of the protons. n gases (plasmas) and electrolytes (e.g. Car batteries), the current is the flow of both positive and negative charges. t is common to refer to a moving charge as a mobile charge carrier. n a metal the charge carriers are electrons. n other conditions or materials, they may be positive or negative ions
5 17.1 Electric Current Example Current in a light bulb The amount of charge that passes through the filament of a certain light bulb in 2.00 s is 1.67 c. Find. () the current in the light bulb. (B) the number of electrons that pass through the filament in 1 second. The amount of charge that passes through the filament of a certain light bulb in 2.00 s is 1.67 c. Find. () the current in the light bulb. ΔQ 1.67C = = = Δt 2.00s The amount of charge that passes through the filament of a certain light bulb in 2.00 s is 1.67 c. Find. (b) the number of electrons that pass through the filament in 1 second. The amount of charge that passes through the filament of a certain light bulb in 2.00 s is 1.67 c. Find. (b) the number of electrons that pass through the filament in 1 second. Reasoning: n 1 s, C of charge passes the cross-sectional sectional area of the filament. This total charge per second is equal to the number of electrons, N, times the charge on a single electron. Solution: 19 ( ) N = N C/ electron = 0.835C q 0.835C N = C/ electron 18 N = electrons
6 17.2 Current and Drift Speed Consider the current on a conductor of cross-sectional sectional area. q v d Δx = v d Δt 17.2 Current and Drift Speed (2) Volume of an element of length Δx is : V = Δx. Let n be the number of carriers per unit of volume. The total number of carriers in V is: n Δx. The charge in this volume is: ΔQ Q = (n Δx)q. Distance traveled at drift speed v d by carrier in time Δt: Δx = v d Δt. Hence: ΔQ Q = (n v d Δt)q. The current through the conductor: = ΔQ/ Δt t = n v d q Current and Drift Speed (3) 17.2 Current and Drift Speed - Example n an isolated conductor, charge carriers move randomly in all directions. When an external potential is applied across the conductor, it creates an electric field inside which produces a force on the electron. Electrons however still have quite a random path. s they travel through the material, electrons collide with other electrons, and nuclei, thereby losing or gaining energy. The work done by the field exceeds the loss by collisions. The electrons then tend to drift preferentially in one direction. Question: copper wire of cross-sectional sectional area 3.00x10-6 m 2 carries a current of 10.. ssuming that each copper atom contributes one free electron to the metal, find the drift speed of the electron in this wire. The e density of copper is 8.95 g/cm
7 Question: copper wire of cross-sectional area 3.00x10-6 m 2 carries a current of 10. ssuming that each copper atom contributes one free electron to the metal, find the drift speed of the electron in this wire. The density of copper is 8.95 g/cm 3. Reasoning: We know: = 3.00x10-6 m 2 = 10. ρ = 8.95 g/cm 3. q = 1.6 x C. n = 6.02x10 23 atom/mol x 8.95 g/cm 3 x ( 63.5 g/mol) -1 n = 8.48 x electrons/ cm 3. Question: copper wire of cross-sectional area 3.00x10-6 m 2 carries a current of 10. ssuming that each copper atom contributes one free electron to the metal, find the drift speed of the electron in this wire. The density of copper is 8.95 g/cm 3. ngredients: = 3.00x10-6 m 2 ; = 10.; ρ = 8.95 g/cm 3.; q = 1.6 x C. n = 8.48 x electrons/cm 3 = 8.48 x electrons/m C/ s vd = = nq electrons m C m ( 28 3 )( )( ) / = m s Current and Drift Speed - Comments Mini-quiz Drift speeds are usually very small. Drift speed much smaller than the average speed between collisions. Electrons traveling at 2.46x10-4 m/s would would take 68 min to travel 1m. So why does light turn on so quickly when one flips a switch? The info travels at roughly 10 8 m/s Consider a wire has a long conical shape. How does the velocity of the electrons vary along the wire? Every portion of the wire carries the same current: as the cross sectional area decreases, the drift velocity must increase to carry the same value of current. This is dues to the electrical field lines being compressed into a smaller area, thereby increasing the strength of the electric field
8 17.4 Resistance and Ohm s s Law - ntro 17.4 Definition of Resistance When a voltage (potential difference) is applied across the ends of a metallic conductor, the current is found to be proportional to the applied voltage. n situations where the proportionality is exact, one can write. Δ V = R The proportionality constant R is called resistance of the conductor. The resistance is defined as the ratio. R = Resistance - Units 17.4 Ohm s s Law n S, resistance is expressed in volts per ampere. special name is given: ohms (Ω).( Example: if a potential difference of 10 V applied across a conductor produces a 0.2 current, then one concludes the conductors has a resistance of 10 V / 0.2 = 50 Ω. Resistance in a conductor arises because of collisions between electrons and fixed charges within the material. n many materials, including most metals, the resistance is constant over a wide range of applied voltages. This is a statement of Ohm s s law. Georg Simon Ohm ( )
9 Linear or Ohmic Material Non-Linear or Non-Ohmic Material Ohm s Law Δ V = R R understood to be independent of. Most metals, ceramics Semiconductors e.g. diodes Definition: Example: Resistance of a Steam ron Resistor: a conductor that provides a specified resistance in an electric circuit. The symbol for a resistor in circuit diagrams. - V = R E ll household electric devices are required to have a specified resistance (as well as many other characteristics ). Consider that the plate of a certain steam iron states the iron carries a current of 7.40 when connected to a 120 V source. What is the resistance of the steam iron? 120V R = = = 16.2 Ω
10 17.5 Resistivity - ntro Electrons moving inside a conductor subject to an external potential constantly collide with atoms of the conductor. They lose energy and are repeated re-accelerated by the electric field produced by the external potential. The collision process is equivalent to an internal friction. This is the origin of a material s resistance Resistivity - Definition The resistance of an ohmic conductor is proportional to the its length, l,, and inversely proportional to the cross section area,,, of the conductor. l R = ρ The constant of proportionality ρ is called the resistivity of the material Resistivity - Remarks 17.5 Resistivity - Units Every material has a characteristic resistivity that depends on its electronic structure, and the temperature. Good conductors have low resistivity. nsulators have high resistivity. nalogy to the flow of water through a pipe. l R = ρ ρ = R l Resistance expressed in Ohms, Length in meter. rea are m 2, Resistivity thus has units of Ωm
11 Resistivity of various materials (also see table 17.1) Material Resistivity (10-8 Ωm) Material Resistivity (10-8 Ωm) Silver 1.61 Bismuth Copper 1.70 Plutonium Gold 2.20 Graphite 1375 luminum 2.65 Germanium 4.6x10 7 Pure 3.5 Diamond 2.7x10 9 Silicon Calcium 3.91 Deionized 1.8x10 13 water Sodium 4.75 odine 1.3x10 15 Tungsten 5.3 Phosphorus 1x10 17 Brass 7.0 Quartz 1x10 21 Uranium 30.0 lumina 1x10 22 Mercury 98.4 Sulfur 2x Mini-quiz Why do old light bulbs give less light than when new? nswer: The filament of a light bulb, made of tungsten, is kept at high temperature when the light bulb is on. t tends to evaporate, i.e. to become thinner, thus decreasing in radius, and cross sectional area. ts resistance increases with time. The current going though the filament then decreases with time and so does its luminosity. Tungsten atoms evaporate off the filament and end up on the inner surface of the bulb. Over time, the glass becomes less transparent and therefore less luminous Resistivity - Example (a) Calculate the resistance per unit length of a 22-gauge nichrome wire of radius m. = πr = π m = m Cross section: ( ) Resistivity (Table): 1.5 x 10 6 Ωm. 6 Resistance/unit length: R ρ Ωm = = = l m Ω m 17.5 Resistivity - Example (b) f a potential difference of 10.0 V is maintained across a 1.0-m length of the nichrome wire, what is the current? 10.0V = = = 2.2 R 4.6Ω
12 17.6 Temperature Variation of Resistance -ntro... next lecture The resistivity of a metal depends on many (environmental) factors. The most important factor is the temperature. For most metals, the resistivity increases with increasing temperature. The increased resistivity arises because of larger friction caused by the more violent motion of the atoms of the metal
General Physics (PHY 2140)
General Physics (PHY 2140) Lecture 7 Electrostatics and electrodynamics Capacitance and capacitors capacitors with dielectrics Electric current current and drift speed resistance and Ohm s law http://www.physics.wayne.edu/~apetrov/phy2140/
More informationUniversity 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 informationChapter 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 informationCapacitors (Chapter 26)
Capacitance, C Simple capacitive circuits Parallel circuits Series circuits Combinations Electric energy Dielectrics Capacitors (Chapter 26) Capacitors What are they? A capacitor is an electric device
More informationChapter 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 informationChapter 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 information6 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 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 informationElectric 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 informationChapter 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 information5. 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 informationChapter 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 informationCurrent. source charges. test charg. 1. Charges in motion
Current 1. Charges in motion 1. Cause of motion 2. Where is it going? 3. Let's keep this going. 2. Current 1. Flow of particles in pipes. 2. A constant problem 3. Conservation Laws 4. Microscopic motion
More informationPhysics 1502: Lecture 8 Today s Agenda. Today s Topic :
Physics 1502: Lecture 8 Today s Agenda Announcements: Lectures posted on: www.phys.uconn.edu/~rcote/ HW assignments, solutions etc. Homework #3: On Masterphysics today: due next Friday Go to masteringphysics.com
More informationand 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 informationELECTRICITY & CIRCUITS
ELECTRICITY & CIRCUITS Reason and justice tell me there s more love for humanity in electricity and steam than in chastity and vegetarianism. Anton Chekhov LIGHTNING, PART 2 Electricity is really just
More information9/22/16 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 informationELECTRICITY & MAGNETISM NOTES
ELECTRICITY & MAGNETISM NOTES PHYSICS B4B BAKERSFIELD COLLEGE Rick Darke (Instructor) CHARGE Electric charge is a fundamental property associated with 2 of the 3 subatomic particles making up most matter.
More information3 Electric current, resistance, energy and power
3 3.1 Introduction Having looked at static charges, we will now look at moving charges in the form of electric current. We will examine how current passes through conductors and the nature of resistance
More informationChapter 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 informationGeneral Physics (PHY 2140)
General Physics (PHY 240) Lecture 5 Electrodynamics Electric current temperature variation of resistance electrical energy and power Direct current circuits emf resistors in series http://www.physics.wayne.edu/~alan/240website/main.htm
More informationPhysics 2212 GJ Quiz #3 Solutions Fall I. (16 points) The electric potential in a certain region of space depends on position according to
Physics 2212 GJ Quiz #3 Solutions Fall 2015 I. (16 points The electric potential in a certain region of space depends on position according to V (x, y, z = ( 2.0 V/m 2 ( x 2 + y 2 ( z + (3.0 V sin + 6.0
More informationResistivity and Temperature Coefficients (at 20 C)
Homework # 4 Resistivity and Temperature Coefficients (at 0 C) Substance Resistivity, Temperature ( m) Coefficient, (C ) - Conductors Silver.59 x 0-0.006 Copper.6 x 0-0.006 Aluminum.65 x 0-0.0049 Tungsten
More informationFrom last time. Today: More on electric potential and connection to E-field How to calculate E-field from V Capacitors and Capacitance
From last time More on electric potential and connection to Efield How to calculate Efield from V Capacitors and Capacitance Today: More on Capacitors and Capacitance Energy stored in Capacitors Current
More informationGeneral Physics (PHY 2140)
General Physics (PHY 2140) Lecture 9 Electrodynamics Electric current temperature variation of resistance electrical energy and power http://www.physics.wayne.edu/~apetrov/phy2140/ Chapter 17-18 1 Department
More informationEnergy Stored in Capacitors
Energy Stored in Capacitors U = 1 2 qv q = CV U = 1 2 CV 2 q 2 or U = 1 2 C 37 Energy Density in Capacitors (1) We define the, u, as the electric potential energy per unit volume Taking the ideal case
More informationPhysics 2102 Gabriela González
Physics 2102 Gabriela González Any two charged conductors form a capacitor. Capacitance : C= Q/V Simple Capacitors: Parallel plates: C = ε 0 A/d Spherical : C = ε 0 4πab/(b-a) Cylindrical: C = ε 0 2πL/ln(b/a)
More informationAgenda for Today. Elements of Physics II. Capacitors Parallel-plate. Charging of capacitors
Capacitors Parallel-plate 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 information10/14/2018. 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 informationPhysics 2220 Fall 2010 George Williams SECOND MIDTERM - REVIEW PROBLEMS
Physics 0 Fall 010 George Williams SECOND MIDTERM - REVIEW PROBLEMS The last four problems are from last years second midterm. Solutions are available on the class web site.. There are no solutions for,
More informationMonday July 14. Capacitance demo slide 19 Capacitors in series and parallel slide 33 Elmo example
Monday July 14 Lecture 5 Capacitance demo slide 19 Capacitors in series and parallel slide 33 Elmo example Lecture 6 Currents and esistance Lecture 9 Circuits Wear Microphone 1 3 Lecture 6 Current and
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 cross-sectional area of the conductor changes. If a conductor has no current,
More informationChapter 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 informationElectric Currents and Simple Circuits
-1 Electric Currents and Simple Circuits Electrons can flow along inside a metal wire if there is an E-field present to push them along ( F= qe). The flow of electrons in a wire is similar to the flow
More informationLecture 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 informationElectricity Electrostatics Types of materials Charging an Object Van de Graaff Generator
Electricity Electricity is the physical phenomena associated with the position or movement of electric charge. The study of electricity is generally divided into two areas electrostatics and current electricity.
More informationChapter 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 informationDirect 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 informationDr. Todd Satogata (ODU/Jefferson Lab) Wednesday, February
University Physics 227N/232N Capacitors, Field Energy, Current and Ohm s Law Lab deferred to Fri Feb 28 QUIZ this Friday! (Feb 21) Fred lectures Monday! (Feb 24) Dr. Todd Satogata (ODU/Jefferson Lab) satogata@jlab.org
More informationElectric Current & DC Circuits How to Use this File Electric Current & DC Circuits Click on the topic to go to that section Circuits
Slide 1 / 127 Slide 2 / 127 Electric Current & DC Circuits www.njctl.org Slide 3 / 127 How to Use this File Slide 4 / 127 Electric Current & DC Circuits Each topic is composed of brief direct instruction
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 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 informationReview. Multiple Choice Identify the letter of the choice that best completes the statement or answers the question.
Review Multiple Choice Identify the letter of the choice that best completes the statement or answers the question. 1. When more devices are added to a series circuit, the total circuit resistance: a.
More informationLouisiana State University Physics 2102, Exam 2, March 5th, 2009.
PRINT Your Name: Instructor: Louisiana State University Physics 2102, Exam 2, March 5th, 2009. Please be sure to PRINT your name and class instructor above. The test consists of 4 questions (multiple choice),
More informationAP 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 informationElectric Charges & Current. Chapter 12. Types of electric charge
Electric Charges & Current Chapter 12 Types of electric charge Protons w/ + charge stuck in the nucleus Electrons w/ - charge freely moving around the nucleus in orbits 1 Conductors Allow the easy flow
More informationCurrent 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 informationQuestion 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 informationLesson 3. Electric Potential. Capacitors Current Electricity
Electric Potential Lesson 3 Potential Differences in a Uniform Electric Field Electric Potential and Potential Energy The Millikan Oil-Drop Experiment Capacitors Current Electricity Ohm s Laws Resistance
More informationPhysics 1202: Lecture 4 Today s Agenda. Today s Topic :
Physics 1202: Lecture 4 Today s Agenda Announcements: Lectures posted on: www.phys.uconn.edu/~rcote/ HW assignments, solutions etc. Homework #1: On Masterphysics: due this coming Friday Go to the syllabus
More informationCurrent and Resistance
PHYS102 Previous Exam Problems CHAPTER 26 Current and Resistance Charge, current, and current density Ohm s law Resistance Power Resistance & temperature 1. A current of 0.300 A is passed through a lamp
More informationGeneral Physics II (PHYS 104) Exam 2: March 21, 2002
General Physics II (PHYS 104) Exam 2: March 21, 2002 Name: Multiple Choice (3 points each): Answer the following multiple choice questions. Clearly circle the response (or responses) that provides the
More informationPhysics 2401 Summer 2, 2008 Exam II
Physics 2401 Summer 2, 2008 Exam II e = 1.60x10-19 C, m(electron) = 9.11x10-31 kg, ε 0 = 8.845x10-12 C 2 /Nm 2, k e = 9.0x10 9 Nm 2 /C 2, m(proton) = 1.67x10-27 kg. n = nano = 10-9, µ = micro = 10-6, m
More informationElectric 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 informationCh. 17: Current & Resistance
Ch. 17: Current & Resistance Current: Rate at which charge flows through an area A (cross-section of a wire) Flow is assumed to be perpendicular to area. Units = Coul/sec = Amp. Remember: I is defined
More informationElectric 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 informationAlgebra Based Physics
Page 1 of 105 Algebra Based Physics Electric Current & DC Circuits 2015-10-06 www.njctl.org Page 2 of 105 Electric Current & DC Circuits Circuits Conductors Resistivity and Resistance Circuit Diagrams
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 informationCHAPTER 4 DC Electricity
CHAPTER 4 DC Electricity Benjamin Franklin proved an important scientific point, which is that electricity originates inside clouds. There, it forms into lightning, which is attracted to the earth by golfers.
More informationChapter 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 informationiclicker A metal ball of radius R has a charge q. Charge is changed q -> - 2q. How does it s capacitance changed?
1 iclicker A metal ball of radius R has a charge q. Charge is changed q -> - 2q. How does it s capacitance changed? q A: C->2 C0 B: C-> C0 C: C-> C0/2 D: C->- C0 E: C->-2 C0 2 iclicker A metal ball of
More informationCircuits. Electric Current & DC Circuits. Slide 1 / 127. Slide 2 / 127. Slide 3 / 127. Slide 4 / 127. Slide 5 / 127. Slide 6 / 127
Slide 1 / 127 Slide 2 / 127 New Jersey Center for Teaching and Learning Electric Current & DC Circuits www.njctl.org Progressive Science Initiative This material is made freely available at www.njctl.org
More informationElectric 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 informationPhysics 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 informationELECTRIC 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 informationPHYS 1444 Section 004 Lecture #10
PHYS 1444 Section 004 Lecture #10 Dr. Electric Current and Resistance The Battery Ohm s Law: Resisters Resistivity Electric Power Alternating Current Power Delivered by AC Today s homework is #6, due 10pm,
More informationCurrent and Resistance. PHY2049: Chapter 26 1
Current and Resistance PHY2049: Chapter 26 1 What You Will Learn in This Chapter Nature of electric current Drift speed, current and current density Current and voltage measurements Conductivity and resistivity
More informationDEVIL PHYSICS THE BADDEST CLASS ON CAMPUS IB PHYSICS
DEL PHYSCS THE BADDEST CLASS ON CAMPUS B PHYSCS TSOKOS LESSON 5-4: ELECTRC CURRENT AND ELECTRC RESSTANCE Reading Activity Questions? Objectives By the end of this class you should be able to: Q State the
More informationConducting surface - equipotential. Potential varies across the conducting surface. Lecture 9: Electrical Resistance.
Lecture 9: Electrical Resistance Electrostatics (time-independent E, I = 0) Stationary Currents (time-independent E and I 0) E inside = 0 Conducting surface - equipotential E inside 0 Potential varies
More informationWhat are the two types of current? The two types of current are direct current and alternating current.
Electric Current What are the two types of current? The two types of current are direct current and alternating current. Electric Current The continuous flow of electric charge is an electric current.
More informationAP 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 informationElectric charges. Basics of Electricity
Electric charges Basics of Electricity Electron has a negative charge Neutron has a no charge Proton has a positive charge But what is a charge? Electric charge, like mass, is a fundamental property of
More informationPHY2054 Summer 2006 Exam 1 06 June 2006
PHY2054 Summer 2006 Exam 1 06 June 2006 Solutions Unless otherwise indicated, (1) is the correct answer. Solutions are, of necessity (due to the writer's self-taught & primitive word-processing skills),
More informationChapter 20 Electric Circuits
Chapter 0 Electric Circuits Chevy olt --- Electric vehicle of the future Goals for Chapter 9 To understand the concept of current. To study resistance and Ohm s Law. To observe examples of electromotive
More informationCHAPTER 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 informationSection 1: Electric Fields
PHY 132 Outline of Lecture Notes i Section 1: Electric Fields A property called charge is part of the basic nature of protons and electrons. Large scale objects become charged by gaining or losing electrons.
More informationChapter 1 The Electric Force
Chapter 1 The Electric Force 1. Properties of the Electric Charges 1- There are two kinds of the electric charges in the nature, which are positive and negative charges. - The charges of opposite sign
More information8. Electric circuit: The closed path along which electric current flows is called an electric circuit.
GIST OF THE LESSON 1. Positive and negative charges: The charge acquired by a glass rod when rubbed with silk is called positive charge and the charge acquired by an ebonite rod when rubbed with wool is
More informationELECTRICITY. 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 informationNews. Charge and Potential. Charge Density. Charge and Potential Quiz #2: Monday, 3/14, 10AM Same procedure as for quiz R +
News Charge and Potential Quiz #2: Monday, 3/14, 10AM Same procedure as for quiz 1 Review in class Fri, 3/11 Evening review, Fri, 3/11, 68PM 2 practice quizzes ( practice problems) Formula sheet R Charged
More informationChapter 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 informationChapter 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 informationChapter 17 Current and Resistance
Chapter 17 Current and Resistance Current Practical applications were based on static electricity. A steady source of electric current allowed scientists to learn how to control the flow of electric charges
More informationElectricity
Electricity Electric Charge There are two fundamental charges in the universe. Positive (proton) has a charge of +1.60 x 10-19 C Negative (electron) has a charge of 1.60 x 10-19 C There is one general
More informationHandout 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 informationName: Class: Date: Multiple Choice Identify the letter of the choice that best completes the statement or answers the question.
Name: Class: Date: AP REVIEW 4 Multiple Choice Identify the letter of the choice that best completes the statement or answers the question. 1. If a positively charged glass rod is used to charge a metal
More informationCh. 21: Current, Resistance, Circuits
Ch. 21: Current, Resistance, Circuits Current: How charges flow through circuits Resistors: convert electrical energy into thermal/radiative energy Electrical Energy & Power; Household Circuits Time-Dependent
More informationBROCK UNIVERSITY. Physics 1P22/1P92. Mid-term Test 2: 19 March Solutions
BROCK UNIVERSITY Physics 1P22/1P92 Mid-term Test 2: 19 March 2010 Solutions 1. [6 marks] (See Page 746, CP # 24, and pages 15 16 of the posted Ch. 22 lecture notes from 4 March.) A 3.0 V potential difference
More informationPhysics 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 informationElectricity MR. BANKS 8 TH GRADE SCIENCE
Electricity MR. BANKS 8 TH GRADE SCIENCE Electric charges Atoms and molecules can have electrical charges. These are caused by electrons and protons. Electrons are negatively charged. Protons are positively
More informationLecture 20. March 22/24 th, Capacitance (Part I) Chapter , Pages
Lecture 0 March /4 th, 005 Capacitance (Part I) Reading: Boylestad s Circuit Analysis, 3 rd Canadian Edition Chapter 10.1-6, Pages 8-94 Assignment: Assignment #10 Due: March 31 st, 005 Preamble: Capacitance
More informationChapter 17 Electric Potential
Chapter 17 Electric Potential Units of Chapter 17 Electric Potential Energy and Potential Difference Relation between Electric Potential and Electric Field Equipotential Lines The Electron Volt, a Unit
More information1 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 informationAgenda for Today. Elements of Physics II. Capacitors Parallel-plate. Charging of capacitors
Capacitors Parallel-plate 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 informationElectric 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 informationPHYS 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 informationElectric Current. Chapter. Activity 1
Chapter 11 n previous classes, you had learnt about electric current, battery, electric circuit and its components. What do you mean by electric current? Which type of charge (positive or negative) flows
More informationPhysics 115. Energy in E fields Electric Current Batteries Resistance. General Physics II. Session 21
Physics 115 General Physics II Session 21 Energy in E fields Electric Current Batteries Resistance R. J. Wilkes Email: phy115a@u.washington.edu Home page: http://courses.washington.edu/phy115a/ 5/6/14
More informationChapter 20. Capacitors, Resistors and Batteries
Chapter 20 Capacitors, Resistors and Batteries How is Discharging Possible?! E Positive and negative charges are attracted to each other: how can they leave the plates? Fringe field is not zero! Electrons
More informationElectric Potential Energy Chapter 16
Electric Potential Energy Chapter 16 Electric Energy and Capacitance Sections: 1, 2, 4, 6, 7, 8, 9 The electrostatic force is a conservative force It is possible to define an electrical potential energy
More information