Major Concepts of Physics PHY102 – Lecture #  Syracuse University Lecture #2 Magnetic fields and forces January 25 th, 2016 Prof. Liviu Movileanu Room 211, Physics Bldg., Major Concepts of Physics PHY102

Major Concepts of Physics PHY102 – Lecture #  Syracuse University Lecture objectives Magnetic Fields Magnetic Force on a Point Charge Motion of a Charged Particle in a Magnetic Field Lecture demonstrations Conceptual Examples Planning/Announcements/Assignments

Major Concepts of Physics PHY102 – Lecture #  Syracuse University §19.1 Magnetic Fields  All magnets have at least one north pole and one south pole.  Field lines emerge from north poles and enter through south poles.  Magnetic Dipole

Major Concepts of Physics PHY102 – Lecture #  Syracuse University Field lines inside and outside the magnet

Major Concepts of Physics PHY102 – Lecture #  Syracuse University Magnetic forces can be both attractive and repulsive  Magnets exert forces on one another.  Opposite magnetic poles attract and like magnetic poles repel.  Magnetic field lines are closed loops. There is no (known!) source of magnetic field lines. (No magnetic monopoles)  If a magnet is broken in half, then you just end up with two magnets.

Major Concepts of Physics PHY102 – Lecture #  Syracuse University Types of waves  Near the surface of the Earth, the magnetic field is that of a dipole.  Note the orientation of the magnetic poles!  Away from the Earth, the magnetic field is distorted by the solar wind. Evidence for magnetic pole reversals has been found on the ocean floor. The iron bearing minerals in the rock contain a record of the Earth’s magnetic field.

Major Concepts of Physics PHY102 – Lecture #  Syracuse University Magnetotactic bacteria

Major Concepts of Physics PHY102 – Lecture #  Syracuse University §19.2 Magnetic Force on a Point Charge  v B The magnitude of F B is: where vsin  is the component of the velocity perpendicular to the direction of the magnetic field.  represents the angle between vectors v and B. Draw the vectors tail-to-tail to determine .

Fig Major Concepts of Physics PHY102 – Lecture #  Syracuse University

Major Concepts of Physics PHY102 – Lecture #  Syracuse University What is vectorial or cross product? For a general cross product:

Ex Major Concepts of Physics PHY102 – Lecture #  Syracuse University

Major Concepts of Physics PHY102 – Lecture #  Syracuse University Conceptual example continuation

Ex Major Concepts of Physics PHY102 – Lecture #  Syracuse University

Major Concepts of Physics PHY102 – Lecture #  Syracuse University Conceptual example Continuation

Major Concepts of Physics PHY102 – Lecture #  Syracuse University 1.This week we will have the first workshop (Workshop #1), titled “Electric Motor” 1.Read textbook materials, pp Sections 19.1 Magnetic fields pp Magnetic force pp Conceptual examples 19.1, Wednesday, January 27 th, you will get your first HW assignments, which will be due on the lab session on the next week.Announcements