Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Magnets and the magnetic field Electric currents create magnetic fields Magnetic fields of wires, loops, and solenoids Magnetic forces on charges and currents Magnets and magnetic materials Chapter 24 Magnetic Fields and Forces Topics: Sample question: This image of a patient’s knee was made with magnetic fields, not x rays. How can we use magnetic fields to visualize the inside of the body? Slide 24-1
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Reading Quiz 1.What is the SI unit for the strength of the magnetic field? Slide 24-2
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Reading Quiz 2.What is the shape of the trajectory that a charged particle follows when it moves perpendicular to a uniform magnetic field? Slide 24-3
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Reading Quiz 3.The magnetic field of a straight, current-carrying wire is A.parallel to the wire. B.perpendicular to the wire. C.around the wire. D.inside the wire. E.zero. Slide 24-4
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. 3.The magnetic field of a straight, current-carrying wire is C.around the wire. Slide 24-5 Answer
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Discovering Magnetism Slide 24-6
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. The Magnetic Field Slide 24-7
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Mapping Out the Field of a Bar Magnet Slide 24-8
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Mapping Out the Magnetic Field Using Iron Filings Slide 24-9
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Drawing Field Lines of a Bar Magnet Slide 24-10
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Magnetic Fields Produced by Bar Magnets A single bar magnet (closeup) Slide 24-11
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Magnetic Fields Produced by Bar Magnets Two bar magnets, unlike poles facing Two bar magnets, like poles facing Slide 24-12
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Checking Understanding Slide 24-13
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Magnetic Fields Around Us Slide 24-14
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Electric Currents Also Create Magnetic Fields A long, straight wire A current loopA solenoid Slide 24-15
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. The Magnetic Field of a Straight Current-Carrying Wire Slide 24-16
Slide 24-17
Representing Vectors and Currents That Are Perpendicular to the Page Slide 24-18
Checking Understanding Point P is 5 cm above the wire as you look straight down at it. In which direction is the magnetic field at P? Slide 24-19
Answer Point P is 5 cm above the wire as you look straight down at it. In which direction is the magnetic field at P? Slide 24-20
Drawing Field Vectors and Field Lines of a Current-Carrying Wire Slide 24-21
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Drawing a Current Loop Slide 24-22
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. The Magnetic Field of a Current Loop Slide 24-23
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. The Magnetic Field of a Solenoid A short solenoidA long solenoid Slide 24-24
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. The Magnitude of the Field due to a Long, Straight, Current-Carrying Wire Slide 24-25
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Slide 24-26
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Checking Understanding A.10 A to the right. B.5 A to the right. C.2.5 A to the right. D.10 A to the left. E.5 A to the left. F.2.5 A to the left. The magnetic field at point P is zero. What are the magnitude and direction of the current in the lower wire? Slide 24-27
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. E.5 A to the left. The magnetic field at point P is zero. What are the magnitude and direction of the current in the lower wire? Slide Answer
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. The Magnetic Field of a Current Loop Magnetic field at the center of a current loop of radius R Magnetic field at the center of a current loop with N turns Slide 24-29
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Example What is the direction and magnitude of the magnetic field at point P, at the center of the loop? Slide 24-30
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. The Magnetic Field Inside a Solenoid Magnetic field inside a solenoid of length L with N turns. Slide 24-31
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. The Force on a Charged Particle Moving in a Magnetic Field Slide 24-32
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. The Right-Hand Rule for Forces Slide 24-33
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Slide 24-34
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Paths of Charged Particles in Magnetic Fields Slide 24-35
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. The Mass Spectrometer Slide 24-36
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Magnetic Fields Exert Forces on Currents Magnitude of the force on a current segment of length L perpendicular to a magnetic field Slide 24-37
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Forces between Currents Slide Magnetic force between two parallel current-carrying wires
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Slide 24-39
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Forces between Current Loops Slide 24-40
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. A Current Loop Acts like a Bar Magnet Slide 24-41
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Magnetic Fields Exert Torques on Current Loops Slide 24-42
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. The Torque on a Dipole in a Magnetic Field Slide 24-43
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Magnetic Resonance Imaging Slide 24-44
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Magnetic Resonance Imaging Slide 24-45
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. The Electric Motor Slide 24-46
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Electron Magnetic Moments: Ferromagnetism A nonmagnetic solid (copper)A ferromagnetic solid (iron) Slide 24-47
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Inducing a Magnetic Moment in a Piece of Iron Slide 24-48