1. Major Concepts of Physics PHY102 – Lecture #2 1 2016  Syracuse University Lecture #3 Magnetic fields and forces January 27 th, 2016 Prof. Liviu Movileanu http://movileanulab.syr.edu/MajorConceptsPhysics2016.html lmovilea@syr.edu Room 211, Physics Bldg., 443-8078 Major Concepts of Physics PHY102

2. Major Concepts of Physics PHY102 – Lecture #3 2 2016  Syracuse University What’s the link for the ebook? Here is the correct link for Physics 3/e http://connect.mheducation.com/class/movileanuspring2016

3. Major Concepts of Physics PHY102 – Lecture #3 3 2016  Syracuse University Lecture objectives Motion of a Charged Particle in a Magnetic Field – Continuation Magnetic force on a current-carrying wire Lecture demonstrations Conceptual Examples Announcements/Homework Assignment

4. Major Concepts of Physics PHY102 – Lecture #3 4 2016  Syracuse University

5. Major Concepts of Physics PHY102 – Lecture #3 5 2016  Syracuse University Why do we have a tilt of the magnetic field? Cross-product

6. Major Concepts of Physics PHY102 – Lecture #3 6 2016  Syracuse University Conceptual example 19.2 - Continuation

7. Example (text problem 19.20): An electron moves with speed 2.0  10 5 m/s in a 1.2 Tesla uniform magnetic field. At one instant, the electron is moving due west and experiences an upward magnetic force of 3.2  10  14 N. What is the direction of the magnetic field? v (west) F (up) y x   The angle can be either north of west OR north of east. Major Concepts of Physics PHY102 – Lecture #3 7 2016  Syracuse University north east

8. § 19.3 Charged Particle Moving Perpendicular to a Uniform B-field A positively charged particle has a velocity v (orange arrow) as shown. The magnetic field is into the page. The magnetic force, at this instant, is shown in blue. In this region of space, this positive charge will move in a circular path. Major Concepts of Physics PHY102 – Lecture #3 8 2016  Syracuse University v FBFB

9. Applying Newton’s 2 nd Law to the charge: Major Concepts of Physics PHY102 – Lecture #3 9 2016  Syracuse University Conceptual example

10. Mass Spectrometer A charged particle is shot into a region of known magnetic field. Here, Particles of different mass will travel different distances before striking the detector. (v, B, and q can be controlled.) V Detector B Major Concepts of Physics PHY102 – Lecture #3 10 2016  Syracuse University

11. Other devices that use magnetic fields to bend particle paths are cyclotrons and synchrotrons. Cyclotrons are used in the production of radioactive nuclei. For medical uses see the website of the Nuclear Energy Institute.Nuclear Energy Institute Synchrotrons are being tested for use in treating tumors. Major Concepts of Physics PHY102 – Lecture #3 11 2016  Syracuse University Conceptual example 19.2 - Continuation

12. Fig. 19.17 Major Concepts of Physics PHY102 – Lecture #3 12 2016  Syracuse University Ernest Lawrence 1929 - Cyclotron

13. Major Concepts of Physics PHY102 – Lecture #3 13 2016  Syracuse University Proton-beam radiosurgery

14. § 19.6 Magnetic Force on a Current Carrying Wire The force on a current carrying wire in an external magnetic field is L is a vector that points in the direction of the current flow. Its magnitude is the length of the wire. Major Concepts of Physics PHY102 – Lecture #3 14 2016  Syracuse University

15. The magnitude of is and its direction is given by the right-hand rule. Major Concepts of Physics PHY102 – Lecture #3 15 2016  Syracuse University Conceptual example 19.2 - Continuation

16. Example (text problem 19.50): A 20.0 cm by 30.0 cm loop of wire carries 1.0 A of current clockwise. (a) Find the magnetic force on each side of the loop if the magnetic field is 2.5 T to the left. I = 1.0 A B Left: F out of page Top: no force Right: F into page Bottom: no force Major Concepts of Physics PHY102 – Lecture #3 16 2016  Syracuse University Conceptual example 19.50 L1L1 L2L2

17. The magnitudes of the nonzero forces are: (b) What is the net force on the loop? Example continued: Major Concepts of Physics PHY102 – Lecture #3 17 2016  Syracuse University Conceptual example 19.2 - Continuation

18. Fig. 19.17 Major Concepts of Physics PHY102 – Lecture #3 18 2016  Syracuse University

19. Major Concepts of Physics PHY102 – Lecture #2 19 2016  Syracuse University 1.This week we will have the first workshop (Workshop #1), titled “Electric Motor” 1.Read textbook materials, pp. 707-717. 2.Sections 19.3 Charged particle moving perpendicularly to a uniform magnetic field pp. 717-718, 720-721 19.6 Magnetic force on a current-carrying wire pp. 727-729 Conceptual examples 19.2, 19.3, 19.8 3. Homework assignment HW #1 is due on next week’s lab sessions. This is Problems 1-8 on pages 745-746 of the text.Announcements