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. 3-D arrows and Cross Products Slide 24-2
Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Electric vs. Magnetic Interactions 1.Nature of Magnetic Interactions Slide 24-2
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