# Chapter 19 Magnetism Magnets Poles of a magnet are the ends where objects are most strongly attracted Two poles, called north and south Like poles

Save this PDF as:

Size: px
Start display at page:

Download "Chapter 19 Magnetism Magnets Poles of a magnet are the ends where objects are most strongly attracted Two poles, called north and south Like poles"

## Transcription

1 Chapter 19 Magnetism Magnets Poles of a magnet are the ends where objects are most strongly attracted Two poles, called north and south Like poles repel each other and unlike poles attract each other Similar to electric charges Magnetic poles cannot be isolated If a permanent magnetic is cut in half repeatedly, you will still have a north and a south pole This differs from electric charges There is some theoretical basis for monopoles, but none have been detected More About Magnetism An unmagnetized piece of iron can be magnetized by stroking it with a magnet Somewhat like stroking an object to charge it Magnetism can be induced If a piece of iron, for example, is placed near a strong permanent magnet, it will become magnetized Types of Magnetic Materials Soft magnetic materials, such as iron, are easily magnetized They also tend to lose their magnetism easily Hard magnetic materials, such as cobalt and nickel, are difficult to magnetize They tend to retain their magnetism Sources of Magnetic Fields The region of space surrounding a moving charge includes a magnetic field The charge will also be surrounded by an electric field A magnetic field surrounds a properly magnetized magnetic material Magnetic Fields A vector quantity Symbolized by Direction is given by the direction a north pole of a compass needle points in that location Magnetic field lines can be used to show how the field lines, as traced out by a compass, would look Magnetic Field Lines, sketch A compass can be used to show the direction of the magnetic field lines (a) A sketch of the magnetic field lines (b) Magnetic Field Lines, Bar Magnet Iron filings are used to show the pattern of the magnetic field lines The direction of the field is the direction a north pole would point Magnetic Field Lines, Unlike Poles Iron filings are used to show the pattern of the magnetic field lines The direction of the field is the direction a north pole would point Compare to the magnetic field produced by an electric dipole Magnetic Field Lines, Like Poles Iron filings are used to show the pattern of the electric field lines The direction of the field is the direction a north pole would point Compare to the electric field produced by like charges Earth s Magnetic Field The Earth s geographic north pole corresponds to a magnetic south pole The Earth s geographic south pole corresponds to a magnetic north pole Strictly speaking, a north pole should be a north-seeking pole and a south pole a south-seeking pole Earth s Magnetic Field The Earth s magnetic field resembles that achieved by burying a huge bar magnet deep in the Earth s interior Dip Angle of Earth s Magnetic Field If a compass is free to rotate vertically as well as horizontally, it points to the earth s surface The angle between the horizontal and the direction of the magnetic field is called the dip angle Dip Angle, cont The farther north the device is moved, the farther from horizontal the compass needle would be The compass needle would be horizontal at the equator and the dip angle would be 0 The compass needle would point straight down at the south magnetic pole and the dip angle would be 90 More About the Earth s Magnetic Poles

2 The dip angle of 90 is found at a point just north of Hudson Bay in Canada This is considered to be the location of the south magnetic pole The magnetic and geographic poles are not in the same exact location The difference between true north, at the geographic north pole, and magnetic north is called the magnetic declination The amount of declination varies by location on the earth s surface Earth s Magnetic Declination Source of the Earth s Magnetic Field There cannot be large masses of permanently magnetized materials since the high temperatures of the core prevent materials from retaining permanent magnetization The most likely source of the Earth s magnetic field is believed to be electric currents in the liquid part of the core Reversals of the Earth s Magnetic Field The direction of the Earth s magnetic field reverses every few million years Evidence of these reversals are found in basalts resulting from volcanic activity The origin of the reversals is not understood Magnetic Fields When a charged particle is moving through a magnetic field, a magnetic force acts on it This force has a maximum value when the charge moves perpendicularly to the magnetic field lines This force is zero when the charge moves along the field lines Magnetic Fields, cont One can define a magnetic field in terms of the magnetic force exerted on a test charge moving in the field with velocity Similar to the way electric fields are defined Units of Magnetic Field The SI unit of magnetic field is the Tesla (T) Wb is a Weber The cgs unit is a Gauss (G) 1 T = 10 4 G A Few Typical B Values Conventional laboratory magnets G or 2.5 T Superconducting magnets G or 30 T Earth s magnetic field 0.5 G or 5 x 10-5 T Finding the Direction of Magnetic Force Experiments show that the direction of the magnetic force is always perpendicular to both and F max occurs when is perpendicular to F = 0 when is parallel to Right Hand Rule #1 Point your fingers in the direction of Curl the fingers in the direction of the magnetic field, Your thumb points in the direction of the force,, on a positive charge If the charge is negative, the force is opposite that determined by the right hand rule Magnetic Force on a Current Carrying Conductor A force is exerted on a current-carrying wire placed in a magnetic field The current is a collection of many charged particles in motion The direction of the force is given by right hand rule #1 Force on a Wire The blue x s indicate the magnetic field is directed into the page The x represents the tail of the arrow Blue dots would be used to represent the field directed out of the page The represents the head of the arrow In this case, there is no current, so there is no force Force on a Wire, cont B is into the page

3 The current is up the page The force is to the left Force on a Wire, final B is into the page The current is down the page The force is to the right Force on a Wire, equation The magnetic force is exerted on each moving charge in the wire The total force is the sum of all the magnetic forces on all the individual charges producing the current F = B I l sin θ θ is the angle between and the direction of I The direction is found by the right hand rule, placing your fingers in the direction of I instead of Torque on a Current Loop t = B I AN sin q Applies to any shape loop N is the number of turns in the coil Torque has a maximum value of NBIA When q = 90 Torque is zero when the field is parallel to the plane of the loop Magnetic Moment The vector is called the magnetic moment of the coil Its magnitude is given by m = IAN The vector always points perpendicular to the plane of the loop(s) The angle is between the moment and the field The equation for the magnetic torque can be written as t = mb sinq Electric Motor An electric motor converts electrical energy to mechanical energy The mechanical energy is in the form of rotational kinetic energy An electric motor consists of a rigid current-carrying loop that rotates when placed in a magnetic field Electric Motor, 2 The torque acting on the loop will tend to rotate the loop to smaller values of θ until the torque becomes 0 at θ = 0 If the loop turns past this point and the current remains in the same direction, the torque reverses and turns the loop in the opposite direction Electric Motor, 3 To provide continuous rotation in one direction, the current in the loop must periodically reverse In ac motors, this reversal naturally occurs In dc motors, a split-ring commutator and brushes are used Actual motors would contain many current loops and commutators Electric Motor, final Just as the loop becomes perpendicular to the magnetic field and the torque becomes 0, inertia carries the loop forward and the brushes cross the gaps in the ring, causing the current loop to reverse its direction This provides more torque to continue the rotation The process repeats itself Force on a Charged Particle in a Magnetic Field Consider a particle moving in an external magnetic field so that its velocity is perpendicular to the field The force is always directed toward the center of the circular path The magnetic force causes a centripetal acceleration, changing the direction of the velocity of the particle Force on a Charged Particle Equating the magnetic and centripetal forces: Solving for r: r is proportional to the momentum of the particle and inversely proportional to the magnetic field Sometimes called the cyclotron equation Particle Moving in an External Magnetic Field If the particle s velocity is not perpendicular to the field, the path followed by the particle is a spiral The spiral path is called a helix Hans Christian Oersted

4 Best known for observing that a compass needle deflects when placed near a wire carrying a current First evidence of a connection between electric and magnetic phenomena Magnetic Fields Long Straight Wire A current-carrying wire produces a magnetic field The compass needle deflects in directions tangent to the circle The compass needle points in the direction of the magnetic field produced by the current Direction of the Field of a Long Straight Wire Right Hand Rule #2 Grasp the wire in your right hand Point your thumb in the direction of the current Your fingers will curl in the direction of the field Magnitude of the Field of a Long Straight Wire The magnitude of the field at a distance r from a wire carrying a current of I is µ o = 4 x 10-7 T. m / A µ o is called the permeability of free space André-Marie Ampère Credited with the discovery of electromagnetism Relationship between electric currents and magnetic fields Ampère s Law Ampère found a procedure for deriving the relationship between the current in an arbitrarily shaped wire and the magnetic field produced by the wire Ampère s Circuital Law B Δl = µ o I Sum over the closed path Ampère s Law, cont Choose an arbitrary closed path around the current Sum all the products of B Δl around the closed path Ampère s Law to Find B for a Long Straight Wire Use a closed circular path The circumference of the circle is 2 r This is identical to the result previously obtained Magnetic Force Between Two Parallel Conductors The force on wire 1 is due to the current in wire 1 and the magnetic field produced by wire 2 The force per unit length is: Force Between Two Conductors, cont Parallel conductors carrying currents in the same direction attract each other Parallel conductors carrying currents in the opposite directions repel each other Defining Ampere and Coulomb The force between parallel conductors can be used to define the Ampere (A) If two long, parallel wires 1 m apart carry the same current, and the magnitude of the magnetic force per unit length is 2 x 10-7 N/m, then the current is defined to be 1 A The SI unit of charge, the Coulomb (C), can be defined in terms of the Ampere If a conductor carries a steady current of 1 A, then the quantity of charge that flows through any cross section in 1 second is 1 C Magnetic Field of a Current Loop The strength of a magnetic field produced by a wire can be enhanced by forming the wire into a loop All the segments, Δx, contribute to the field, increasing its strength Magnetic Field of a Current Loop Total Field Magnetic Field of a Current Loop Equation The magnitude of the magnetic field at the center of a circular loop with a radius R and carrying current I is With N loops in the coil, this becomes Magnetic Field of a Solenoid If a long straight wire is bent into a coil of several closely spaced loops, the resulting device is called a solenoid It is also known as an electromagnet since it acts like a magnet only when it carries a current Magnetic Field of a Solenoid, 2

5 The field lines inside the solenoid are nearly parallel, uniformly spaced, and close together This indicates that the field inside the solenoid is nearly uniform and strong The exterior field is nonuniform, much weaker, and in the opposite direction to the field inside the solenoid Magnetic Field in a Solenoid, 3 The field lines of a closely spaced solenoid resemble those of a bar magnet Magnetic Field in a Solenoid, Magnitude The magnitude of the field inside a solenoid is constant at all points far from its ends B = µ o n I n is the number of turns per unit length n = N / l The same result can be obtained by applying Ampère s Law to the solenoid Magnetic Field in a Solenoid from Ampère s Law A cross-sectional view of a tightly wound solenoid If the solenoid is long compared to its radius, we assume the field inside is uniform and outside is zero Apply Ampère s Law to the blue dashed rectangle Gives same result as previously found Magnetic Effects of Electrons Orbits An individual atom should act like a magnet because of the motion of the electrons about the nucleus Each electron circles the atom once in about every seconds This would produce a current of 1.6 ma and a magnetic field of about 20 T at the center of the circular path However, the magnetic field produced by one electron in an atom is often canceled by an oppositely revolving electron in the same atom Magnetic Effects of Electrons Orbits, cont The net result is that the magnetic effect produced by electrons orbiting the nucleus is either zero or very small for most materials Magnetic Effects of Electrons Spins Electrons also have spin The classical model is to consider the electrons to spin like tops It is actually a quantum effect Magnetic Effects of Electrons Spins, cont The field due to the spinning is generally stronger than the field due to the orbital motion Electrons usually pair up with their spins opposite each other, so their fields cancel each other That is why most materials are not naturally magnetic Magnetic Effects of Electrons Domains In some materials, the spins do not naturally cancel Such materials are called ferromagnetic Large groups of atoms in which the spins are aligned are called domains When an external field is applied, the domains that are aligned with the field tend to grow at the expense of the others This causes the material to become magnetized Domains, cont Random alignment (left) shows an unmagnetized material When an external field is applied, the domains aligned with B grow (right) Domains and Permanent Magnets In hard magnetic materials, the domains remain aligned after the external field is removed The result is a permanent magnet In soft magnetic materials, once the external field is removed, thermal agitation causes the materials to quickly return to an unmagnetized state With a core in a loop, the magnetic field is enhanced since the domains in the core material align, increasing the magnetic field Types of Magnetic Materials Ferromagnetic Have permanent magnetic moments that align readily with an externally applied magnetic field Paramagnetic Have magnetic moments that tend to align with an externally applied magnetic field, but the response is weak compared to a ferromagnetic material Diamagnetic

6 An externally applied field induces a very weak magnetization that is opposite the direction of the applied field

### Chapter 27 Magnetic Field and Magnetic Forces

Chapter 27 Magnetic Field and Magnetic Forces - Magnetism - Magnetic Field - Magnetic Field Lines and Magnetic Flux - Motion of Charged Particles in a Magnetic Field - Applications of Motion of Charged

### Chapter 14 Magnets and

Chapter 14 Magnets and Electromagnetism How do magnets work? What is the Earth s magnetic field? Is the magnetic force similar to the electrostatic force? Magnets and the Magnetic Force! We are generally

### Chapter 21. Magnetic Forces and Magnetic Fields

Chapter 21 Magnetic Forces and Magnetic Fields 21.1 Magnetic Fields The needle of a compass is permanent magnet that has a north magnetic pole (N) at one end and a south magnetic pole (S) at the other.

### Force on a square loop of current in a uniform B-field.

Force on a square loop of current in a uniform B-field. F top = 0 θ = 0; sinθ = 0; so F B = 0 F bottom = 0 F left = I a B (out of page) F right = I a B (into page) Assume loop is on a frictionless axis

### Magnetic Force. For centuries, humans observed strange force. Between iron and special stones called lodestones. Force couldn't be gravity or electric

MAGNETIC FIELD Magnetic Force For centuries, humans observed strange force Between iron and special stones called lodestones Force couldn't be gravity or electric Not enough mass or electric charge to

### Magnetism. d. gives the direction of the force on a charge moving in a magnetic field. b. results in negative charges moving. clockwise.

Magnetism 1. An electron which moves with a speed of 3.0 10 4 m/s parallel to a uniform magnetic field of 0.40 T experiences a force of what magnitude? (e = 1.6 10 19 C) a. 4.8 10 14 N c. 2.2 10 24 N b.

### Name: Date: Regents Physics Mr. Morgante UNIT 4B Magnetism

Name: Regents Physics Date: Mr. Morgante UNIT 4B Magnetism Magnetism -Magnetic Force exists b/w charges in motion. -Similar to electric fields, an X stands for a magnetic field line going into the page,

### MAGNETISM MAGNETISM. Principles of Imaging Science II (120)

Principles of Imaging Science II (120) Magnetism & Electromagnetism MAGNETISM Magnetism is a property in nature that is present when charged particles are in motion. Any charged particle in motion creates

### Module 3 : Electromagnetism Lecture 13 : Magnetic Field

Module 3 : Electromagnetism Lecture 13 : Magnetic Field Objectives In this lecture you will learn the following Electric current is the source of magnetic field. When a charged particle is placed in an

### Chapter 19: Magnetic Forces and Fields

Chapter 19: Magnetic Forces and Fields Magnetic Fields Magnetic Force on a Point Charge Motion of a Charged Particle in a Magnetic Field Crossed E and B fields Magnetic Forces on Current Carrying Wires

### 1. The diagram below represents magnetic lines of force within a region of space.

1. The diagram below represents magnetic lines of force within a region of space. 4. In which diagram below is the magnetic flux density at point P greatest? (1) (3) (2) (4) The magnetic field is strongest

### General Physics (PHY 2140)

General Physics (PHY 2140) Lecture 12 Electricity and Magnetism Magnetism Magnetic fields and force Application of magnetic forces http://www.physics.wayne.edu/~apetrov/phy2140/ Chapter 19 1 Department

### My lecture slides are posted at Information for Physics 112 midterm, Wednesday, May 2

My lecture slides are posted at http://www.physics.ohio-state.edu/~humanic/ Information for Physics 112 midterm, Wednesday, May 2 1) Format: 10 multiple choice questions (each worth 5 points) and two show-work

### Eðlisfræði 2, vor 2007

[ Assignment View ] [ Pri Eðlisfræði 2, vor 2007 28. Sources of Magnetic Field Assignment is due at 2:00am on Wednesday, March 7, 2007 Credit for problems submitted late will decrease to 0% after the deadline

### Chapter 22 Magnetism

22.6 Electric Current, Magnetic Fields, and Ampere s Law Chapter 22 Magnetism 22.1 The Magnetic Field 22.2 The Magnetic Force on Moving Charges 22.3 The Motion of Charged particles in a Magnetic Field

### PHYS-2020: General Physics II Course Lecture Notes Section V

PHYS-2020: General Physics II Course Lecture Notes Section V Dr. Donald G. Luttermoser East Tennessee State University Edition 4.0 Abstract These class notes are designed for use of the instructor and

### Magnetism. Magnetism. Magnetic Fields and Magnetic Domains. Magnetic Fields and Magnetic Domains. Creating and Destroying a Magnet

Magnetism Magnetism Opposite poles attract and likes repel Opposite poles attract and likes repel Like electric force, but magnetic poles always come in pairs (North, South) Like electric force, but magnetic

### Chapter 22: Electric motors and electromagnetic induction

Chapter 22: Electric motors and electromagnetic induction The motor effect movement from electricity When a current is passed through a wire placed in a magnetic field a force is produced which acts on

### Fall 12 PHY 122 Homework Solutions #8

Fall 12 PHY 122 Homework Solutions #8 Chapter 27 Problem 22 An electron moves with velocity v= (7.0i - 6.0j)10 4 m/s in a magnetic field B= (-0.80i + 0.60j)T. Determine the magnitude and direction of the

### Chapter 30 - Magnetic Fields and Torque. A PowerPoint Presentation by Paul E. Tippens, Professor of Physics Southern Polytechnic State University

Chapter 30 - Magnetic Fields and Torque A PowerPoint Presentation by Paul E. Tippens, Professor of Physics Southern Polytechnic State University 2007 Objectives: After completing this module, you should

### Conceptual: 1, 3, 5, 6, 8, 16, 18, 19. Problems: 4, 6, 8, 11, 16, 20, 23, 27, 34, 41, 45, 56, 60, 65. Conceptual Questions

Conceptual: 1, 3, 5, 6, 8, 16, 18, 19 Problems: 4, 6, 8, 11, 16, 20, 23, 27, 34, 41, 45, 56, 60, 65 Conceptual Questions 1. The magnetic field cannot be described as the magnetic force per unit charge

### Magnetic Fields. I. Magnetic Field and Magnetic Field Lines

Magnetic Fields I. Magnetic Field and Magnetic Field Lines A. The concept of the magnetic field can be developed in a manner similar to the way we developed the electric field. The magnitude of the magnetic

### Physics 30 Worksheet #10 : Magnetism From Electricity

Physics 30 Worksheet #10 : Magnetism From Electricity 1. Draw the magnetic field surrounding the wire showing electron current below. x 2. Draw the magnetic field surrounding the wire showing electron

### 1. Units of a magnetic field might be: A. C m/s B. C s/m C. C/kg D. kg/c s E. N/C m ans: D

Chapter 28: MAGNETIC FIELDS 1 Units of a magnetic field might be: A C m/s B C s/m C C/kg D kg/c s E N/C m 2 In the formula F = q v B: A F must be perpendicular to v but not necessarily to B B F must be

### ELECTRICITYt. Electromagnetism

ELECTRICITYt Electromagnetism Subject area : Physics Topic focus : magnetic properties, magnetic field, the Earth s magnetic field, magnetic field of an electric wire. Learning Aims : Polarity of bar magnets

### TIME OF COMPLETION DEPARTMENT OF NATURAL SCIENCES. PHYS 2212, Exam 2 Section 1 Version 1 April 16, 2014 Total Weight: 100 points

TIME OF COMPLETION NAME DEPARTMENT OF NATURAL SCIENCES PHYS 2212, Exam 2 Section 1 Version 1 April 16, 2014 Total Weight: 100 points 1. Check your examination for completeness prior to starting. There

### physics 112N magnetic fields and forces

physics 112N magnetic fields and forces bar magnet & iron filings physics 112N 2 bar magnets physics 112N 3 the Earth s magnetic field physics 112N 4 electro -magnetism! is there a connection between electricity

### Magnetic Dipoles. Recall that an electric dipole consists of two equal but opposite charges separated by some distance, such as in

MAGNETISM History of Magnetism Bar Magnets Magnetic Dipoles Magnetic Fields Magnetic Forces on Moving Charges and Wires Electric Motors Current Loops and Electromagnets Solenoids Sources of Magnetism Spin

### Magnetic Field and Magnetic Forces

Chapter 27 Magnetic Field and Magnetic Forces PowerPoint Lectures for University Physics, Thirteenth Edition Hugh D. Young and Roger A. Freedman Lectures by Wayne Anderson Goals for Chapter 27 Magnets

### Chapter 33. The Magnetic Field

Chapter 33. The Magnetic Field Digital information is stored on a hard disk as microscopic patches of magnetism. Just what is magnetism? How are magnetic fields created? What are their properties? These

### Magnets and the Magnetic Force

Magnets and the Magnetic Force We are generally more familiar with magnetic forces than with electrostatic forces. Like the gravitational force and the electrostatic force, this force acts even when the

### Review Questions PHYS 2426 Exam 2

Review Questions PHYS 2426 Exam 2 1. If 4.7 x 10 16 electrons pass a particular point in a wire every second, what is the current in the wire? A) 4.7 ma B) 7.5 A C) 2.9 A D) 7.5 ma E) 0.29 A Ans: D 2.

### Chapter 24 Practice Problems, Review, and Assessment

Section 1 Understanding Magnetism: Practice Problems 1. If you hold a bar magnet in each hand and bring your hands close together, will the force be attractive or repulsive if the magnets are held in the

### Force on Moving Charges in a Magnetic Field

[ Assignment View ] [ Eðlisfræði 2, vor 2007 27. Magnetic Field and Magnetic Forces Assignment is due at 2:00am on Wednesday, February 28, 2007 Credit for problems submitted late will decrease to 0% after

### CET Moving Charges & Magnetism

CET 2014 Moving Charges & Magnetism 1. When a charged particle moves perpendicular to the direction of uniform magnetic field its a) energy changes. b) momentum changes. c) both energy and momentum

### Lab 9 Magnetic Interactions

Lab 9 Magnetic nteractions Physics 6 Lab What You Need To Know: The Physics Electricity and magnetism are intrinsically linked and not separate phenomena. Most of the electrical devices you will encounter

### * Biot Savart s Law- Statement, Proof Applications of Biot Savart s Law * Magnetic Field Intensity H * Divergence of B * Curl of B. PPT No.

* Biot Savart s Law- Statement, Proof Applications of Biot Savart s Law * Magnetic Field Intensity H * Divergence of B * Curl of B PPT No. 17 Biot Savart s Law A straight infinitely long wire is carrying

### Question Details C14: Magnetic Field Direction Abbott [ ]

Phys 1114: Assignment 9 Abbott (5420633) Due: Mon Apr 7 2014 11:59 PM CDT Question 1 2 3 4 5 6 7 8 9 10 11 1. Question Details C14: Magnetic Field Direction Abbott [2861537] a) A wire is oriented horizontally

### Magnetism Basics. Magnetic Domains: atomic regions of aligned magnetic poles Random Alignment Ferromagnetic Alignment. Net Effect = Zero!

Magnetism Basics Source: electric currents Magnetic Domains: atomic regions of aligned magnetic poles Random Alignment Ferromagnetic Alignment Net Effect = Zero! Net Effect = Additive! Bipolar: all magnets

### Physics 126 Practice Exam #3 Professor Siegel

Physics 126 Practice Exam #3 Professor Siegel Name: Lab Day: 1. Which one of the following statements concerning the magnetic force on a charged particle in a magnetic field is true? A) The magnetic force

### Magnetism: a new force!

-1 Magnetism: a new force! So far, we'e learned about two forces: graity and the electric field force. =, = Definition of -field kq -fields are created by charges: = r -field exerts a force on other charges:

### Maxwell s Equations ( ) : q ε. Gauss's law electric. Gauss's law in (magnetic): B da= Faraday's law: Ampere-Maxwell law

Our Goal: Maxwell s Equations ( ) : Gauss's law electric E da= Gauss's law in (magnetic): B da= 0 Faraday's law: Ampere-Maxwell law S S q ε o dφ E ds= dt B B ds= μ I + μ o o dφ dt E Electric Force and

### (1) Physics Purpose: Materials: Theory: We investigate the elementary properties of magnetism using the following four magnets:

Department of Physics and Geology The study of magnetic fields Physics 2402 Purpose: We investigate the elementary properties of magnetism using the following four magnets: 1. a compass needle 2. a bar

### MAGNETIC EFFECTS OF ELECTRIC CURRENT

CHAPTER 13 MAGNETIC EFFECT OF ELECTRIC CURRENT In this chapter, we will study the effects of electric current : 1. Hans Christian Oersted (1777-1851) Oersted showed that electricity and magnetism are related

### Solution: (a) For a positively charged particle, the direction of the force is that predicted by the right hand rule. These are:

Problem 1. (a) Find the direction of the force on a proton (a positively charged particle) moving through the magnetic fields as shown in the figure. (b) Repeat part (a), assuming the moving particle is

### 11. Sources of Magnetic Fields

11. Sources of Magnetic Fields S. G. Rajeev February 24, 2009 1 Magnetic Field Due to a Straight Wire We saw that electric currents produce magnetic fields. The simplest situation is an infinitely long,

### " - angle between l and a R

Magnetostatic Fields According to Coulomb s law, any distribution of stationary charge produces a static electric field (electrostatic field). The analogous equation to Coulomb s law for electric fields

### PY106 Class13. Permanent Magnets. Magnetic Fields and Forces on Moving Charges. Interactions between magnetic north and south poles.

Permanent Magnets Magnetic ields and orces on Moing Charges 1 We encounter magnetic fields frequently in daily life from those due to a permanent magnet. Each permanent magnet has a north pole and a south

### CHARGE TO MASS RATIO OF THE ELECTRON

CHARGE TO MASS RATIO OF THE ELECTRON In solving many physics problems, it is necessary to use the value of one or more physical constants. Examples are the velocity of light, c, and mass of the electron,

### Inductance. Motors. Generators

Inductance Motors Generators Self-inductance Self-inductance occurs when the changing flux through a circuit arises from the circuit itself. As the current increases, the magnetic flux through a loop due

### Two bar magnets are brought near each other as shown. The magnets... A) attract B) repel C) exert no net force on each other.

Magnetic Fields and Forces Learning goals: Students will be able to Predict the direction of the magnet field for different locations around a bar magnet and an electromagnet. Relate magnetic field strength

### Chapter 8: Magnetism

8.1 The Force on a Charge in a Magnetic Field - The Definition of the Magnetic Field esides the existence of electric fields in nature, there are also magnetic fields. Most students have seen and played

### Chapter 4. Magnetic Materials and Circuits

Chapter 4 Magnetic Materials and Circuits Objectives List six characteristics of magnetic field. Understand the right-hand rule for current and magnetic fluxes. Define magnetic flux, flux density, magnetomotive

### Magnetism, a history. Existence of a Magnetic Field, B. Magnetic Force on a charged particle. The particle in the figure

Existence of a Magnetic Field, B Magnetic field, B, is a vector You may be familiar with bar magnets have a magnetic field similar to electric field of dipoles Amazing experimental finding: there is a

### Physics 1653 Exam 3 - Review Questions

Physics 1653 Exam 3 - Review Questions 3.0 Two uncharged conducting spheres, A and B, are suspended from insulating threads so that they touch each other. While a negatively charged rod is held near, but

### Physics 112 Homework 5 (solutions) (2004 Fall) Solutions to Homework Questions 5

Solutions to Homework Questions 5 Chapt19, Problem-2: (a) Find the direction of the force on a proton (a positively charged particle) moving through the magnetic fields in Figure P19.2, as shown. (b) Repeat

### The purposes of this experiment are to test Faraday's Law qualitatively and to test Lenz's Law.

260 17-1 I. THEORY EXPERIMENT 17 QUALITATIVE STUDY OF INDUCED EMF Along the extended central axis of a bar magnet, the magnetic field vector B r, on the side nearer the North pole, points away from this

### Motor Fundamentals. DC Motor

Motor Fundamentals Before we can examine the function of a drive, we must understand the basic operation of the motor. It is used to convert the electrical energy, supplied by the controller, to mechanical

### Final Exam (40% of grade) on Monday December 7 th 1130a-230pm in York 2622 You can bring two 8.5x11 pages, front and back, of notes Calculators may

Final Exam (40% of grade) on Monday December 7 th 1130a-230pm in York 2622 You can bring two 8.5x11 pages, front and back, of notes Calculators may be used multiple choice like quizzes, only longer by

### Unit 3 Lesson 4 Magnets and Magnetism. Copyright Houghton Mifflin Harcourt Publishing Company

Stuck on You What are some properties of magnets? The term magnet describes any material that attracts iron or objects made of iron. Many magnets are made of iron, nickel, cobalt, or mixtures of these

### Physics 9 Fall 2009 Homework 7 - Solutions

Physics 9 Fall 009 Homework 7 - s 1. Chapter 33 - Exercise 10. At what distance on the axis of a current loop is the magnetic field half the strength of the field at the center of the loop? Give your answer

### AP2 Magnetism. (c) Explain why the magnetic field does no work on the particle as it moves in its circular path.

A charged particle is projected from point P with velocity v at a right angle to a uniform magnetic field directed out of the plane of the page as shown. The particle moves along a circle of radius R.

### Chapter 29: Magnetic Fields

Chapter 29: Magnetic Fields Magnetism has been known as early as 800C when people realized that certain stones could be used to attract bits of iron. Experiments using magnets hae shown the following:

### Physics 2B. Lecture 29B

Physics 2B Lecture 29B "There is a magnet in your heart that will attract true friends. That magnet is unselfishness, thinking of others first. When you learn to live for others, they will live for you."

### Multiple Choice Questions for Physics 1 BA113 Chapter 23 Electric Fields

Multiple Choice Questions for Physics 1 BA113 Chapter 23 Electric Fields 63 When a positive charge q is placed in the field created by two other charges Q 1 and Q 2, each a distance r away from q, the

### VIII. Magnetic Fields - Worked Examples

MASSACHUSETTS INSTITUTE OF TECHNOLOGY Department of Physics 8.0 Spring 003 VIII. Magnetic Fields - Worked Examples Example : Rolling rod A rod with a mass m and a radius R is mounted on two parallel rails

### Phys102 Lecture 18/19 Ampere's Law

Phys102 Lecture 18/19 Ampere's Law Key Points Ampère s Law Magnetic Field Due to a Straight Wire B Magnetic Field of a Solenoid and a Toroid References SFU Ed: 28-1,2,3,4,5. 6 th Ed: 20-5,6,7. Ampère s

### Question Bank. 1. Electromagnetism 2. Magnetic Effects of an Electric Current 3. Electromagnetic Induction

1. Electromagnetism 2. Magnetic Effects of an Electric Current 3. Electromagnetic Induction 1. Diagram below shows a freely suspended magnetic needle. A copper wire is held parallel to the axis of magnetic

### Physics, Chapter 30: Magnetic Fields of Currents

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Robert Katz Publications Research Papers in Physics and Astronomy 1-1-1958 Physics, Chapter 30: Magnetic Fields of Currents

### LAB 8: Electron Charge-to-Mass Ratio

Name Date Partner(s) OBJECTIVES LAB 8: Electron Charge-to-Mass Ratio To understand how electric and magnetic fields impact an electron beam To experimentally determine the electron charge-to-mass ratio.

### Magnetic fields of charged particles in motion

C H A P T E R 8 Magnetic fields of charged particles in motion CONCEPTS 8.1 Source of the magnetic field 8. Current loops and spin magnetism 8.3 Magnetic moment and torque 8.4 Ampèrian paths QUANTTATVE

### PPT No. 26. Uniformly Magnetized Sphere in the External Magnetic Field. Electromagnets

PPT No. 26 Uniformly Magnetized Sphere in the External Magnetic Field Electromagnets Uniformly magnetized sphere in external magnetic field The Topic Uniformly magnetized sphere in external magnetic field,

### Exam 2 Solutions. PHY2054 Spring Prof. P. Kumar Prof. P. Avery March 5, 2008

Prof. P. Kumar Prof. P. Avery March 5, 008 Exam Solutions 1. Two cylindrical resistors are made of the same material and have the same resistance. The resistors, R 1 and R, have different radii, r 1 and

### Lecture 14. Magnetic Forces on Currents.

Lecture 14. Magnetic Forces on Currents. Outline: Hall Effect. Magnetic Force on a Wire Segment. Torque on a Current-Carrying Loop. Lecture 13: Magnetic Forces on Moving Charges - we considered individual

### Lecture 13. Magnetic Field, Magnetic Forces on Moving Charges. Outline:

Lecture 13. Magnetic Field, Magnetic Forces on Moving Charges. Outline: Intro to Magnetostatics. Magnetic Field Flux, Absence of Magnetic Monopoles. Force on charges moving in magnetic field. 1 Intro to

### Linear DC Motors. 15.1 Magnetic Flux. 15.1.1 Permanent Bar Magnets

Linear DC Motors The purpose of this supplement is to present the basic material needed to understand the operation of simple DC motors. This is intended to be used as the reference material for the linear

### STUDY GUIDE: ELECTRICITY AND MAGNETISM

319 S. Naperville Road Wheaton, IL 60187 www.questionsgalore.net Phone: (630) 580-5735 E-Mail: info@questionsgalore.net Fax: (630) 580-5765 STUDY GUIDE: ELECTRICITY AND MAGNETISM An atom is made of three

### Electricity, Energy and Magnetism

Electricity, Energy and Magnetism A. What's a Magnet? A magnet is a substance with two opposite poles: orth and outh. Like opposite charges, opposite poles attract, so the north pole of one magnet will

### The DC Motor. Physics 1051 Laboratory #5 The DC Motor

The DC Motor Physics 1051 Laboratory #5 The DC Motor Contents Part I: Objective Part II: Introduction Magnetic Force Right Hand Rule Force on a Loop Magnetic Dipole Moment Torque Part II: Predictions Force

### PS-6.2 Explain the factors that determine potential and kinetic energy and the transformation of one to the other.

PS-6.1 Explain how the law of conservation of energy applies to the transformation of various forms of energy (including mechanical energy, electrical energy, chemical energy, light energy, sound energy,

### CHAPTER 5: MAGNETIC PROPERTIES

CHAPTER 5: MAGNETIC PROPERTIES and Magnetic Materials ISSUES TO ADDRESS... Why do we study magnetic properties? What is magnetism? How do we measure magnetic properties? What are the atomic reasons for

### Phys222 Winter 2012 Quiz 4 Chapters 29-31. Name

Name If you think that no correct answer is provided, give your answer, state your reasoning briefly; append additional sheet of paper if necessary. 1. A particle (q = 5.0 nc, m = 3.0 µg) moves in a region

### Chapter 19 Magnetic Forces and Fields

Chapter 19 Magnetic Forces and Fields Student: 3. The magnetism of the Earth acts approximately as if it originates from a huge bar magnet within the Earth. Which of the following statements are true?

### EDEXCEL NATIONAL CERTIFICATE/DIPLOMA UNIT 5 - ELECTRICAL AND ELECTRONIC PRINCIPLES NQF LEVEL 3. OUTCOME 3 - MAGNETISM and INDUCTION

EDEXCEL NATIONAL CERTIFICATE/DIPLOMA UNIT 5 - ELECTRICAL AND ELECTRONIC PRINCIPLES NQF LEVEL 3 OUTCOME 3 - MAGNETISM and INDUCTION 3 Understand the principles and properties of magnetism Magnetic field:

### Magnetic Fields and Their Effects

Name Date Time to Complete h m Partner Course/ Section / Grade Magnetic Fields and Their Effects This experiment is intended to give you some hands-on experience with the effects of, and in some cases

### Magnetic Field & Right Hand Rule. Academic Resource Center

Magnetic Field & Right Hand Rule Academic Resource Center Magnetic Fields And Right Hand Rules By: Anthony Ruth Magnetic Fields vs Electric Fields Magnetic fields are similar to electric fields, but they

### ElectroMagnetic Induction. AP Physics B

ElectroMagnetic Induction AP Physics B What is E/M Induction? Electromagnetic Induction is the process of using magnetic fields to produce voltage, and in a complete circuit, a current. Michael Faraday

### Three types of materials. 1. (Permanent) Magnet 2. Ferromagnertic 3. Non-magnetic

Magnets Weak A magnet is a source of magnetic interactions. The poles of the magnet have the strongest magnetic interaction. There are two types of poles pole and pole. Each magnet has (at least) one pole

### 1) Magnetic field lines come out of the south pole of a magnet and enter at the north pole.

Exam Name 1) Magnetic field lines come out of the south pole of a magnet and enter at the north pole. 2) Which of the following statements is correct? A) Earth's north pole is magnetic north. B) The north

### Quiz: Work and Energy

Quiz: Work and Energy A charged particle enters a uniform magnetic field. What happens to the kinetic energy of the particle? (1) it increases (2) it decreases (3) it stays the same (4) it changes with

### Ampere's Law. Introduction. times the current enclosed in that loop: Ampere's Law states that the line integral of B and dl over a closed path is 0

1 Ampere's Law Purpose: To investigate Ampere's Law by measuring how magnetic field varies over a closed path; to examine how magnetic field depends upon current. Apparatus: Solenoid and path integral

### Preview of Period 16: Motors and Generators

Preview of Period 16: Motors and Generators 16.1 DC Electric Motors What causes the rotor of a motor to spin? 16.2 Simple DC Motors What causes a changing magnetic field in the simple coil motor? 16.3

### Physics 221 Experiment 5: Magnetic Fields

Physics 221 Experiment 5: Magnetic Fields August 25, 2007 ntroduction This experiment will examine the properties of magnetic fields. Magnetic fields can be created in a variety of ways, and are also found

### DIRECT CURRENT GENERATORS

DIRECT CURRENT GENERATORS Revision 12:50 14 Nov 05 INTRODUCTION A generator is a machine that converts mechanical energy into electrical energy by using the principle of magnetic induction. This principle

### Magnetostatics (Free Space With Currents & Conductors)

Magnetostatics (Free Space With Currents & Conductors) Suggested Reading - Shen and Kong Ch. 13 Outline Review of Last Time: Gauss s Law Ampere s Law Applications of Ampere s Law Magnetostatic Boundary

### Mapping the Magnetic Field

I Mapping the Magnetic Field Mapping the Magnetic Field Vector Fields The electric field, E, and the magnetic field, B, are two examples of what are termed vector fields, quantities which have both magnitude

### MAGNETIC FORCE ON AN ELECTRIC CHARGE

DO PHYSICS ONLINE MOTORS AND GENERATORS MAGNETIC ORCE ON AN ELECTRIC CHARGE Experiments show that moing electric charges are deflected in magnetic fields. Hence, moing electric charges experience forces

### 5. Measurement of a magnetic field

H 5. Measurement of a magnetic field 5.1 Introduction Magnetic fields play an important role in physics and engineering. In this experiment, three different methods are examined for the measurement of