# Force on Moving Charges in a Magnetic Field

 To view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video
Save this PDF as:

Size: px
Start display at page:

## Transcription

2 Now consider the example of a positive charge moving in the xy plane with velocity (i.e., with magnitude at angle with respect to the x axis). If the local magnetic field is in the +z direction, what is the direction of the magnetic force acting on the particle? Hint C.1 Finding the cross product The direction can be found by any of the usual means of finding the cross product: 1. Use the determinant expression for the cross product. (See your math or physics text.) 2. Use the general definition where any term with the three directions in the normal order of xyz or any cyclical permutation (e.g., yzx or zxy) has a positive sign, and terms with the other order (xzy, zyx, or yxz) have a negative sign., Express the direction of the force in terms of, as a linear combination of unit vectors,,, and. ANSWER: Direction of = Part D First find the magnitude of the force on a positive charge in the case that the velocity (of magnitude ) and the magnetic field (of magnitude ) are perpendicular. Express your answer in terms of,, statement., and other quantities given in the problem Part E Now consider the example of a positive charge moving in the -z direction with speed with the local magnetic field of magnitude in the +z direction. Find, the magnitude of the magnetic force acting on the particle. Express your answer in terms of,, statement. 0, and other quantities given in the problem There is no magnetic force on a charge moving parallel or antiparallel to the magnetic field. Equivalently, the magnetic force is proportional to the component of velocity perpendicular to the magnetic field. Part F Now consider the case in which the positive charge is moving in the yz plane with a speed at an angle with the z axis as shown (with the magnetic field still in the +z direction with magnitude ). Find the magnetic force on the charge. 2 of 13 17/4/07 16:06

3 Part F.1 Direction of force Part F.2 Relevant component of velocity Express the magnetic force in terms of given variables like,,,, and unit vectors. Electromagnetic Velocity Filter When a particle with charge moves across a magnetic field of magnitude, it experiences a force to the side. If the proper electric field is simultaneously applied, the electric force on the charge will be in such a direction as to cancel the magnetic force with the result that the particle will travel in a straight line. The balancing condition provides a relationship involving the velocity of the particle. In this problem you will figure out how to arrange the fields to create this balance and then determine this relationship. Consider the arrangement of ion source and electric field plates shown in the figure. The ion source sends particles with velocity along the positive x axis. They encounter electric field plates spaced a distance apart that generate a uniform electric field of magnitude in the +y direction. To cancel the resulting electric force with a magnetic force, a magnetic field (not shown) must be added in which direction? Using the right-hand rule, you can see that the positive z axis is directed out of the screen. Hint A.1 Method for determining direction Hint A.2 Right-hand rule Choose the direction of. ANSWER: Answer not displayed Part C A Conductor Moving in a Magnetic Field A metal cube with sides of length is moving at velocity across a uniform magnetic field. The cube is oriented so that four of its edges are parallel to its direction of motion (i.e., the normal vector of two faces are parallel to the direction of motion). 3 of 13 17/4/07 16:06

4 Find, the electric field inside the cube. Hint A.1 Net force on charges in a conductor Electrons in a conductor are more or less free to move within the conductor. As a result electrons in a conductor placed in an electric field (with no magnetic field present) will move until the electic field that they generate inside the conductor cancels the applied field (i.e., until the net internal electric field equals zero). In general, the charges in a conductor move until the net force on them is zero. This happens almost instantaneously in a good conductor. In this problem, there is no external electric field but there is a force on the electrons due to the applied magnetic field. The electrons will thus move in such a way as to create an electric field that will cancel the magnetic force on them (leaving a net force of zero on the electrons)..2 Find the magnetic force magnitude What is, the magnitude of the force due to the magnetic field exerted on an electron with charge inside the cube? Express your answer in terms of some or all of the variables,, and..3 Find the magnetic force direction Use the vector equation field. Remember to use and the right-hand rule to determine the direction of the force from the magnetic for the electron charge. Answer in terms of the unit vectors,, and. ANSWER:.4 Determine the force due to the electric field What is, the force on an electron inside the cube with charge due to an induced electric field? Express your answer in terms of one or both of the variables and. Express the electric field in terms of,, and unit vectors (,, and/or ). Now, instead of electrons, suppose that the free charges have positive charge. Examples include "holes" in semiconductors and positive ions in liquids, each of which act as "conductors" for their free charges. If one replaces the conducting cube with one that has positive charge carriers, in what direction does the induced electric field point? 4 of 13 17/4/07 16:06

5 ANSWER: The direction of the electric field stays the same regardless of the sign of the charges that are free to move in the conductor. Mathematically, you can see that this must be true since the expression you derived for the electric field is independent of. Physically, this is because the force due to the magnetic field changes sign as well and causes positive charges to move in the direction (as opposed to pushing negative charges in the direction). Therefore the result is always the same: positive charges on the side and negative charges on the side. Because the electric field goes from positive to negative charges will always point in the direction (given the original directions of and ). Rail Gun A Rail Gun uses electromagnetic forces to accelerate a projectile to very high velocities. The basic mechanism of acceleration is relatively simple and can be illustrated in the following example. A metal rod of mass and electrical resistance rests on parallel horizontal rails (that have negligible electric resistance), which are a distance apart. The rails are also connected to a voltage source, so a current loop is formed. The rod begins to move if the externally applied vertical magnetic field in which the rod is located reaches the value. Assume that the rod has a slightly flattened bottom so that it slides instead of rolling. Use for the magnitude of the acceleration due to gravity. Find, the coefficient of static friction between the rod and the rails. Hint A.1 How to approach this problem.2 Force due to the magnetic field.3 Frictional force Express the coefficient of static friction in terms of variables given in the introduction. Charge moving in Cyclotron Orbits 5 of 13 17/4/07 16:06

6 Charge Moving in a Cyclotron Orbit Learning Goal: To understand why charged particles move in circles perpendicular to a magnetic field and why the frequency is an invariant. A particle of charge and mass moves in a region of space where there is a uniform magnetic field (i.e., a magnetic field of magnitude the magnetic force. in the +z direction). In this problem, neglect any forces on the particle other than At a given moment the particle is moving in the +x direction (and the magnetic field is always in the +z direction). If is positive, what is the direction of the force on the particle due to the magnetic field? Hint A.1 The right-hand rule for magnetic force ANSWER: Answer not displayed Part C Part D Motion of Electrons in a Magnetic Field An electron of mass and charge is moving through a uniform magnetic field in vacuum. At the origin, it has velocity, where and. A screen is mounted perpendicular to the x axis at a distance from the origin. Throughout, you can assume that the effect of gravity is negligible. First, suppose. Find the y coordinate of the point at which the electron strikes the screen. Hint A.1 Forces acting on electron Hint A.2 Two-dimensional kinematics 6 of 13 17/4/07 16:06

7 Now suppose, and another electron is projected in the same manner. Which of the following is the most accurate qualitative description of the electron's motion once it enters the region of nonzero magnetic field? ANSWER: Answer not displayed Part C Mass Spectrometer J. J. Thomson is best known for his discoveries about the nature of cathode rays. Another important contribution of his was the invention, together with one of his students, of the mass spectrometer. The ratio of mass to (positive) charge of an ion may be accurately determined in a mass spectrometer. In essence, the spectrometer consists of two regions: one that accelerates the ion through a potential and a second that measures its radius of curvature in a perpendicular magnetic field. The ion begins at potential and is accelerated toward zero potential. When the particle exits the region with the electric field it will have obtained a speed. With what speed does the ion exit the acceleration region? Hint A.1 Suggested general method Perhaps the easiest method to use for solving this problem is conservation of energy..2 Initial energy Find the initial total mechanical energy (which includes electric potential energy) of the particle. Express in terms of,,, and any constants..3 Final energy Find, the total mechanical energy of the ion as it exits the region with the electric field (i.e., when it reaches the region of zero electric potential and enters the magnet). Express in terms of,, and any needed constants. Find the speed in terms of,,, and any constants. 7 of 13 17/4/07 16:06

8 After being accelerated, the particle enters a uniform magnetic field of strength and travels in a circle of radius (determined by observing where it hits on a screen--as shown in the figure). The results of this experiment allow one to find in terms of the experimentally measured quantities such as the particle radius, the magnetic field, and the applied voltage. What is?.1 Cyclotron frequency Find the cyclotron frequency, which is the (angular) frequency of the orbital motion of the ion in the magnetic field. There is a skill builder problem on this if you need help. Hint B.1.a General method to find Express the cyclotron frequency in terms of,, and..2 Relationship of and What is the relationship between the cyclotron frequency and the kinematic variables and? (This is the definition of angular speed.) Express in terms of and. Hint B.3 Putting it all together Eliminate from the two equations from the previous hints, and then eliminate using the result of. The result should give in terms of the experimentally measured parameters. Express in terms of,,, and any necessary constants. By sending atoms of various elements through a mass spectrometer, Thomson's student, Francis Aston, discovered that some elements actually contained atoms with several different masses. Atoms of the same element with different masses can only be explained by the existence of a third subatomic particle in addition to protons and electrons: the neutron. Torques on Magnetic Dipoles in Uniform Field Torque on a Current Loop in a Magnetic Field Learning Goal: To understand the origin of the torque on a current loop due to the magnetic forces on the current-carrying wires and to introduce the magnetic moment of the loop. This problem will show you how to calculate the torgue on a magnetic dipole in a uniform magnetic field. We start with a rectangular current loop, the shape of which allows us to calculate the Lorentz forces explicitly. Then we generalize our result. Even if you already know the general formula to solve this problem, you might find it instructive to discover where it comes from. A current flows in a plane rectangular current loop with height and horizontal sides. The loop is placed into a uniform magnetic field in such a way that the sides of length are perpendicular to, and there is an angle between the sides of length and. 8 of 13 17/4/07 16:06

9 Calculate, the magnitude of the torque about the vertical axis of the current loop due to the interaction of the current through the loop with the magnetic field. Hint A.1 How to approach the problem First find the forces (direction and magnitude) on each segment of the loop. Then find the torque due to each force and add them up..2 Forces on the parts of the loop that have length As current is moving through the loop, forces act on its different parts. These result from Lorentz forces on the charges that move through the wire. What is the direction of the forces on the two pieces of wire of length? Hint A.2.a Force on a straight current-carrying wire in a magnetic field The force on a straight wire of length carrying current in a magnetic field is given by. Select the correct diagram from the four options. The forces are symbolized by the red arrows. ANSWER: A B C D The forces on these parts of the loop don't cause a motion of the center of mass, since they are equal and opposite, but they do produce a net torque for general, since their lines of action do not pass through the center of mass of the loop..3 Force on a current-carrying wire in a magnetic field Find, the magnitude of the force on each of the vertical wires (those with length ). Hint A.3.a Relevant equation Express in terms of,,, and. Note that not all of these may appear in the answer..4 Torque on a loop Find, the component of the torque around the vertical axis of the loop (i.e., out of the plane of the top-view figure). Hint A.4.a Definition of torque Express in terms of,, and. 9 of 13 17/4/07 16:06

10 .5 Forces on the parts of the loop that have length As current is moving through the loop, forces act on its different parts. These result from Lorentz forces on the charges that move through the wire. What can you say about the forces on the two pieces of wire of length? Select the most accurate qualitative description from the following list. ANSWER: The forces point away from the center of the loop and cancel each other. The forces act as a torque about an axis through the midpoints of the two two pieces of length b and make the loop turn in the direction of positive. The forces point toward the center of the loop and cancel each other. Both forces point upward perpendicular to and. Since the forces on these two parts of the loop cancel out, and their line of action goes through the center of mass of the loop, we need not consider them in the calculation of the torque on the loop. The key is that the forces are in line, so their torque contributions about any point cancel. Express the magnitude of the torque in terms of the given variables. You will need a trigonomeric function [e.g., or ]. Use for the magnitude of the magnetic field. Give a more general expression for the magnitude of the torque. Rewrite the answer found in in terms of the magnitude of the magnetic dipole moment of the current loop. Define the angle between the vector perpendicular to the plane of the coil and the magnetic field to be, noting that this angle is the complement of angle in. Hint B.1 Definition of the magnetic dipole moment Give your answer in terms of the magnetic moment, magnetic field, and. The more general vector form of this expression is. Part C A current flows around a plane circular loop of radius, giving the loop a magnetic dipole moment of magnitude. The loop is placed in a uniform magnetic field, with an angle between the direction of the field lines and the magnetic dipole moment as shown in the figure. Find an expression for the magnitude of the torque on the current loop. 10 of 13 17/4/07 16:06

11 Hint C.1 Formula for the area of a circle Express the torque explicitly in terms of,,,, and (where and are the magnitudes of the respective vector quantities). Do not use. You will need a trigonomeric function [e.g.. or ]. A DC Motor A shunt-wound DC motor with the field coils and rotor connected in parallel (see the figure) operates from a 115 DC power line. The resistance of the field windings,, is 235. The resistance of the rotor,, is When the motor is running, the rotor develops an emf. The motor draws a current of 4.08 from the line. Friction losses amount to Compute the field current. Hint A.1 Voltages in a parallel circuit Recall that for each element in a parallel circuit there is the same voltage difference between the individual elements. As a result, the same voltage difference of = 115 lies across both the field windings with resistance 235 and the rotor with resistance Hint A.2 Current through a resistor Recall that the current passing through an element with resistance is given by, where is the voltage across the resistor. Express your answer in amperes Compute the rotor current. Hint B.1 Currents in a parallel circuit Recall that for a circuit in parallel, there are multiple paths for the total current to take in getting from the positive electrode of the power supply to the negative electrode. As a result, different amounts of current pass through the elements in a parallel circuit according to the resistance and the voltage differences on each element. The current passing through each of the sections must add up to the total current being supplied by the power supply of 13 17/4/07 16:06

12 Part C Compute the emf. Hint C.1 How to approach the problem Think of the back emf from the rotor as reducing the voltage difference from the power supply across the rotor. You can picture the system diagrammatically by putting the resistance part of the rotor and the back emf part of the rotor in series. This gives you the equation for total voltage across the rotor, where is the voltage from the power supply, is the voltage across the resistance element of the rotor, and is the back emf from the rotor. We already know that, and we can find by using the current calculated in. Hint C.2 Relation between voltage and current 93.5 Part D Compute the rate of development of thermal energy in the field windings. Part D.1 Equation for thermal energy Express your answer in watts Part E Compute the rate of development of thermal energy in the rotor. Part E.1 Equation for thermal energy What is the power dissipated via heat through a resistor of resistance that has a current of passing through it? ANSWER: Express your answer in watts Part F Compute the power input to the motor. Part F.1 Equation for total power input What is the power through an electric circuit of voltage and current? ANSWER: 12 of 13 17/4/07 16:06

13 Express your answer in watts. 469 Part G Compute the efficiency of the motor. Hint G.1 Definition of efficiency The efficiency of an electrical motor (or any motor for that matter) is given by the ratio of the power coming out of the circuit, after all losses are taken into account, and the total power initially supplied to the circuit. This efficiency must be a value less than or equal to one, since the power coming out of the circuit must be less than or equal to the power going in (i.e., the circuit cannot generate its own energy, but can only consume it). ANSWER: Changing Energy of a Magnetic Coil A coil with magnetic moment 1.49 magnetic field of magnitude is oriented initially with its magnetic moment antiparallel to a uniform What is the change in potential energy of the coil when it is rotated 180 degrees, so that its magnetic moment is parallel to the field? Hint A.1 Potential energy for a magnetic dipole Hint A.2 Potential energy difference Hint A.3 Definition of antiparallel Express your answer in joules. ANSWER: Summary 7 of 10 problems complete (67.63% avg. score) of 35 points 13 of 13 17/4/07 16:06

### 1 of 7 4/13/2010 8:05 PM

Chapter 33 Homework Due: 8:00am on Wednesday, April 7, 2010 Note: To understand how points are awarded, read your instructor's Grading Policy [Return to Standard Assignment View] Canceling a Magnetic Field

### Eðlisfræði 2, vor 2007

[ Assignment View ] [ Pri Eðlisfræði 2, vor 2007 29a. Electromagnetic Induction Assignment is due at 2:00am on Wednesday, March 7, 2007 Credit for problems submitted late will decrease to 0% after the

### 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

### 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

### 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

### 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.

### Homework #8 203-1-1721 Physics 2 for Students of Mechanical Engineering. Part A

Homework #8 203-1-1721 Physics 2 for Students of Mechanical Engineering Part A 1. Four particles follow the paths shown in Fig. 32-33 below as they pass through the magnetic field there. What can one conclude

### 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

### 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 Forces and Magnetic Fields

1 Magnets Magnets are metallic objects, mostly made out of iron, which attract other iron containing objects (nails) etc. Magnets orient themselves in roughly a north - south direction if they are allowed

### 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

### 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.

### 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

### 4.1.Motion Of Charged Particles In Electric And Magnetic Field Motion Of Charged Particles In An Electric Field

4.1.Motion Of Charged Particles In Electric And Magnetic Field 4.1.1. Motion Of Charged Particles In An Electric Field A charged particle in an electric field will experience an electric force due to the

### 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

### THE MAGNETIC FIELD. 9. Magnetism 1

THE MAGNETIC FIELD Magnets always have two poles: north and south Opposite poles attract, like poles repel If a bar magnet is suspended from a string so that it is free to rotate in the horizontal plane,

### MOVING CHARGES AND MAGNETISM

MOVING CHARGES AND MAGNETISM 1. A circular Coil of 50 turns and radius 0.2m carries of current of 12A Find (a). magnetic field at the centre of the coil and (b) magnetic moment associated with it. 3 scores

### PSS 27.2 The Electric Field of a Continuous Distribution of Charge

Chapter 27 Solutions PSS 27.2 The Electric Field of a Continuous Distribution of Charge Description: Knight Problem-Solving Strategy 27.2 The Electric Field of a Continuous Distribution of Charge is illustrated.

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

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

### Chapter 14: Magnets and Electromagnetism

Chapter 14: Magnets and Electromagnetism 1. Electrons flow around a circular wire loop in a horizontal plane, in a direction that is clockwise when viewed from above. This causes a magnetic field. Inside

### 2. B The magnetic properties of a material depend on its. A) shape B) atomic structure C) position D) magnetic poles

ame: Magnetic Properties 1. B What happens if you break a magnet in half? A) One half will have a north pole only and one half will have a south pole only. B) Each half will be a new magnet, with both

### Pearson Physics Level 30 Unit VI Forces and Fields: Chapter 12 Solutions

Concept Check (top) Pearson Physics Level 30 Unit VI Forces and Fields: Chapter 1 Solutions Student Book page 583 Concept Check (bottom) The north-seeking needle of a compass is attracted to what is called

### 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

### 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 To study

### Lecture PowerPoints. Chapter 20 Physics: Principles with Applications, 7 th edition Giancoli

Lecture PowerPoints Chapter 20 Physics: Principles with Applications, 7 th edition Giancoli This work is protected by United States copyright laws and is provided solely for the use of instructors in teaching

### 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

### Objectives for the standardized exam

III. ELECTRICITY AND MAGNETISM A. Electrostatics 1. Charge and Coulomb s Law a) Students should understand the concept of electric charge, so they can: (1) Describe the types of charge and the attraction

### Eðlisfræði 2, vor 2007

[ Assignment View ] [ Pri Eðlisfræði 2, vor 2007 31. Alternating Current Circuits Assignment is due at 2:00am on Wednesday, March 21, 2007 Credit for problems submitted late will decrease to 0% after the

### 5.Magnetic Fields due to Currents( with Answers)

5.Magnetic Fields due to Currents( with Answers) 1. Suitable units for µ. Ans: TmA -1 ( Recall magnetic field inside a solenoid is B= µ ni. B is in tesla, n in number of turn per metre, I is current in

### 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

### SPH4U UNIVERSITY PHYSICS

SPH4U UNIVERSITY PHYSICS GRAVITATIONAL, ELECTRIC, &... FIELDS L Magnetic Force on Moving Charges (P.386-391) Particle Accelerators As was stated earlier, the ability to accelerate charged particles with

### E/M Experiment: Electrons in a Magnetic Field.

E/M Experiment: Electrons in a Magnetic Field. PRE-LAB You will be doing this experiment before we cover the relevant material in class. But there are only two fundamental concepts that you need to understand.

### Eðlisfræði 2, vor 2007

[ Assignment View ] [ Print ] Eðlisfræði 2, vor 2007 30. Inductance Assignment is due at 2:00am on Wednesday, March 14, 2007 Credit for problems submitted late will decrease to 0% after the deadline has

### Lesson 12: Magnetic Forces and Circular Motion!

Lesson 12: Magnetic Forces and Circular Motion If a magnet is placed in a magnetic field, it will experience a force. Types of magnets: Direction of the force on a permanent magnet: Direction of the force

### 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

### Chapter 14 Magnets and Electromagnetism

Chapter 14 Magnets and Electromagnetism Magnets and Electromagnetism In the 19 th century experiments were done that showed that magnetic and electric effects were just different aspect of one fundamental

### 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,

### Physics 12 Study Guide: Electromagnetism Magnetic Forces & Induction. Text References. 5 th Ed. Giancolli Pg

Objectives: Text References 5 th Ed. Giancolli Pg. 588-96 ELECTROMAGNETISM MAGNETIC FORCE AND FIELDS state the rules of magnetic interaction determine the direction of magnetic field lines use the right

### Physics 121 Sample Common Exam 3 NOTE: ANSWERS ARE ON PAGE 6. Instructions: 1. In the formula F = qvxb:

Physics 121 Sample Common Exam 3 NOTE: ANSWERS ARE ON PAGE 6 Signature Name (Print): 4 Digit ID: Section: Instructions: Answer all questions 24 multiple choice questions. You may need to do some calculation.

### 2015 Pearson Education, Inc. Section 24.5 Magnetic Fields Exert Forces on Moving Charges

Section 24.5 Magnetic Fields Exert Forces on Moving Charges Magnetic Fields Sources of Magnetic Fields You already know that a moving charge is the creator of a magnetic field. Effects of Magnetic Fields

### 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.

### ConcepTest PowerPoints

ConcepTest PowerPoints Chapter 20 Physics: Principles with Applications, 6 th edition Giancoli 2005 Pearson Prentice Hall This work is protected by United States copyright laws and is provided solely for

### PHY2049 Exam #2 Solutions Fall 2012

PHY2049 Exam #2 Solutions Fall 2012 1. The diagrams show three circuits consisting of concentric circular arcs (either half or quarter circles of radii r, 2r, and 3r) and radial segments. The circuits

### Date: Deflection of an Electron in a Magnetic Field

Name: Partners: Date: Deflection of an Electron in a Magnetic Field Purpose In this lab, we use a Cathode Ray Tube (CRT) to measure the effects of an electric and magnetic field on the motion of a charged

### Concept Review. Physics 1

Concept Review Physics 1 Speed and Velocity Speed is a measure of how much distance is covered divided by the time it takes. Sometimes it is referred to as the rate of motion. Common units for speed or

### 2. In Newton s universal law of gravitation the masses are assumed to be. B. masses of planets. D. spherical masses.

Practice Test: 41 marks (55 minutes) Additional Problem: 19 marks (7 minutes) 1. A spherical planet of uniform density has three times the mass of the Earth and twice the average radius. The magnitude

### My Website:

PH203 Recitation Week 09 Problem Set Spring 2015 Ryan Scheirer Email: scheirer@onid.orst.edu My Website: http://people.oregonstate.edu/~scheirer/ph203_rec.html Problem 01 For the following questions, use

### Gauss's Law. Gauss's Law in 3, 2, and 1 Dimension

[ Assignment View ] [ Eðlisfræði 2, vor 2007 22. Gauss' Law Assignment is due at 2:00am on Wednesday, January 31, 2007 Credit for problems submitted late will decrease to 0% after the deadline has passed.

### Chapter 27 Magnetic Field an Magnetic Forces Study magnetic forces. Consider magnetic field and flux

Chapter 27 Magnetic Field an Magnetic Forces Study magnetic forces Consider magnetic field and flux Explore motion in a magnetic field Consider magnetic torque Apply magnetic principles and study the electric

### Sample Questions for the AP Physics 1 Exam

Sample Questions for the AP Physics 1 Exam Sample Questions for the AP Physics 1 Exam Multiple-choice Questions Note: To simplify calculations, you may use g 5 10 m/s 2 in all problems. Directions: Each

### Magnets. We have all seen the demonstration where you put a magnet under a piece of glass, put some iron filings on top and see the effect.

Magnets We have all seen the demonstration where you put a magnet under a piece of glass, put some iron filings on top and see the effect. What you are seeing is another invisible force field known as

### 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.

### Chapter 29. Magnetic Fields

Chapter 29 Magnetic Fields A Partial History of Magnetism 13 th century BC Chinese used a compass 800 BC Uses a magnetic needle Probably an invention of Arabic or Indian origin Greeks Discovered magnetite

### Solution Derivations for Capa #10

Solution Derivations for Capa #10 1) A 1000-turn loop (radius = 0.038 m) of wire is connected to a (25 Ω) resistor as shown in the figure. A magnetic field is directed perpendicular to the plane of the

### 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

### EXPERIMENT IV. FORCE ON A MOVING CHARGE IN A MAGNETIC FIELD (e/m OF ELECTRON ) AND. FORCE ON A CURRENT CARRYING CONDUCTOR IN A MAGNETIC FIELD (µ o )

1 PRINCETON UNIVERSITY PHYSICS 104 LAB Physics Department Week #4 EXPERIMENT IV FORCE ON A MOVING CHARGE IN A MAGNETIC FIELD (e/m OF ELECTRON ) AND FORCE ON A CURRENT CARRYING CONDUCTOR IN A MAGNETIC FIELD

### Q28.1 A positive point charge is moving to the right. The magnetic field that the point charge produces at point P (see diagram below) P

Q28.1 A positive point charge is moving to the right. The magnetic field that the point charge produces at point P (see diagram below) P r + v r A. points in the same direction as v. B. points from point

### 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

### Test - A2 Physics. Primary focus Magnetic Fields - Secondary focus electric fields (including circular motion and SHM elements)

Test - A2 Physics Primary focus Magnetic Fields - Secondary focus electric fields (including circular motion and SHM elements) Time allocation 40 minutes These questions were ALL taken from the June 2010

### Phys 102 Spg Exam No. 2 Solutions

Phys 102 Spg. 2008 Exam No. 2 Solutions I. (20 pts) A 10-turn wire loop measuring 8.0 cm by 16.0 cm carrying a current of 2.0 A lies in the horizontal plane and is free to rotate about a horizontal axis

### Magnetism Conceptual Questions. Name: Class: Date:

Name: Class: Date: Magnetism 22.1 Conceptual Questions 1) A proton, moving north, enters a magnetic field. Because of this field, the proton curves downward. We may conclude that the magnetic field must

### 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

### PHYS 155: Final Tutorial

Final Tutorial Saskatoon Engineering Students Society eric.peach@usask.ca April 13, 2015 Overview 1 2 3 4 5 6 7 Tutorial Slides These slides have been posted: sess.usask.ca homepage.usask.ca/esp991/ Section

### mv = ev ebr Application: circular motion of moving ions In a uniform magnetic field: The mass spectrometer KE=PE magnitude of electron charge

1.4 The Mass Spectrometer Application: circular motion of moving ions In a uniform magnetic field: The mass spectrometer mv r qb mv eb magnitude of electron charge 1 mv ev KEPE v 1 mv ebr m v e r m B m

### 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

### 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

### Handout 7: Magnetic force. Magnetic force on moving charge

1 Handout 7: Magnetic force Magnetic force on moving charge A particle of charge q moving at velocity v in magnetic field B experiences a magnetic force F = qv B. The direction of the magnetic force is

### Chapter 23 Magnetic Flux and Faraday s Law of Induction

Chapter 23 Magnetic Flux and Faraday s Law of Induction 23.1 Induced EMF 23.2 Magnetic Flux 23.3 Faraday s Law of Induction 23.4 Lenz s Law 23.5 Mechanical Work and Electrical Energy 23.6 Generators and

### Rotational Motion. Description of the motion. is the relation between ω and the speed at which the body travels along the circular path.

Rotational Motion We are now going to study one of the most common types of motion, that of a body constrained to move on a circular path. Description of the motion Let s first consider only the description

### ) 0.7 =1.58 10 2 N m.

Exam 2 Solutions Prof. Paul Avery Prof. Andrey Korytov Oct. 29, 2014 1. A loop of wire carrying a current of 2.0 A is in the shape of a right triangle with two equal sides, each with length L = 15 cm as

### 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

### The Big Idea. Key Concepts

The ig Idea For static electric charges, the electromagnetic force is manifested by the Coulomb electric force alone. If charges are moing, howeer, there is created an additional force, called magnetism.

### Kirchhoff's Rules and Applying Them

[ Assignment View ] [ Eðlisfræði 2, vor 2007 26. DC Circuits Assignment is due at 2:00am on Wednesday, February 21, 2007 Credit for problems submitted late will decrease to 0% after the deadline has passed.

### PHY222 Lab 7 - Magnetic Fields and Right Hand Rules Magnetic forces on wires, electron beams, coils; direction of magnetic field in a coil

PHY222 Lab 7 - Magnetic Fields and Right Hand Rules Magnetic forces on wires, electron beams, coils; direction of magnetic field in a coil Print Your Name Print Your Partners' Names You will return this

### Electricity and Water Analogy

[ Assignment View ] [ Eðlisfræði 2, vor 2007 25. Current, Resistance, and Electromagnetic Force Assignment is due at 2:00am on Wednesday, February 14, 2007 Credit for problems submitted late will decrease

### Physics 9 Fall 2009 Homework 2 - Solutions

Physics 9 Fall 009 Homework - s 1. Chapter 7 - Exercise 5. An electric dipole is formed from ±1.0 nc charges spread.0 mm apart. The dipole is at the origin, oriented along the y axis. What is the electric

### Profs. A. Petkova, A. Rinzler, S. Hershfield. Exam 2 Solution

PHY2049 Fall 2009 Profs. A. Petkova, A. Rinzler, S. Hershfield Exam 2 Solution 1. Three capacitor networks labeled A, B & C are shown in the figure with the individual capacitor values labeled (all units

### AP Physics C Chapter 23 Notes Yockers Faraday s Law, Inductance, and Maxwell s Equations

AP Physics C Chapter 3 Notes Yockers Faraday s aw, Inductance, and Maxwell s Equations Faraday s aw of Induction - induced current a metal wire moved in a uniform magnetic field - the charges (electrons)

### 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

### 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:

### Physics 6C, Summer 2006 Homework 1 Solutions F 4

Physics 6C, Summer 006 Homework 1 Solutions All problems are from the nd edition of Walker. Numerical values are different for each student. Chapter Conceptual Questions 18. Consider the four wires shown

### 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

### 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

### Magnetic Fields; Sources of Magnetic Field

This test covers magnetic fields, magnetic forces on charged particles and current-carrying wires, the Hall effect, the Biot-Savart Law, Ampère s Law, and the magnetic fields of current-carrying loops

### Lesson 5 Rotational and Projectile Motion

Lesson 5 Rotational and Projectile Motion Introduction: Connecting Your Learning The previous lesson discussed momentum and energy. This lesson explores rotational and circular motion as well as the particular

### Physics 210 Q ( PHYSICS210BRIDGE ) My Courses Course Settings

1 of 16 9/7/2012 1:10 PM Logged in as Julie Alexander, Instructor Help Log Out Physics 210 Q1 2012 ( PHYSICS210BRIDGE ) My Courses Course Settings Course Home Assignments Roster Gradebook Item Library

### 104 Practice Exam 2-3/21/02

104 Practice Exam 2-3/21/02 1. Two electrons are located in a region of space where the magnetic field is zero. Electron A is at rest; and electron B is moving westward with a constant velocity. A non-zero

### 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

### Chapter 18 Electric Forces and Electric Fields. Key Concepts:

Chapter 18 Lectures Monday, January 25, 2010 7:33 AM Chapter 18 Electric Forces and Electric Fields Key Concepts: electric charge principle of conservation of charge charge polarization, both permanent

### Essential Physics II. Lecture 8:

Essential Physics II E II Lecture 8: 16-12-15 News Schedule change: Monday 7th December ( ) NO CLASS! Thursday 26th November ( ) 18:15-19:45 This week s homework: 11/26 (next lecture) Next week s homework:

### Lab 4: Magnetic Force on Electrons

Lab 4: Magnetic Force on Electrons Introduction: Forces on particles are not limited to gravity and electricity. Magnetic forces also exist. This magnetic force is known as the Lorentz force and it is

### Physics 25 Exam 3 November 3, 2009

1. A long, straight wire carries a current I. If the magnetic field at a distance d from the wire has magnitude B, what would be the the magnitude of the magnetic field at a distance d/3 from the wire,

### Physics 2212 GH Quiz #4 Solutions Spring 2015

Physics 1 GH Quiz #4 Solutions Spring 15 Fundamental Charge e = 1.6 1 19 C Mass of an Electron m e = 9.19 1 31 kg Coulomb constant K = 8.988 1 9 N m /C Vacuum Permittivity ϵ = 8.854 1 1 C /N m Earth s

### Worked solutions Chapter 9 Magnets and electricity

9.1 Fundamentals of magnetism 1 A magnetic field exists at any point in space where a magnet or magnetic material (e.g. iron, nickel, cobalt) will experience a magnetic force. 2 C. The magnetic force between

### Practice final for Basic Physics spring 2005 answers on the last page Name: Date:

Practice final for Basic Physics spring 2005 answers on the last page Name: Date: 1. A 12 ohm resistor and a 24 ohm resistor are connected in series in a circuit with a 6.0 volt battery. Assuming negligible

### Magnetic Fields. David J. Starling Penn State Hazleton PHYS 212

Magnetism, as you recall from physics class, is a powerful force that causes certain items to be attracted to refrigerators. - Dave Barry David J. Starling Penn State Hazleton PHYS 212 Objectives (a) Determine

### 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,