# Magnetic Fields Tanya Liu. Some Expectations Participate! Please don’t be scared, I would like to hear everyone’s voice Once again, if you don’t understand.

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Magnetic Fields Tanya Liu

Some Expectations Participate! Please don’t be scared, I would like to hear everyone’s voice Once again, if you don’t understand me, just raise your hand There will be some short assignments given All my slides will be uploaded to Professor Dodero’s site: http://my.liceti.it/prof/dodero/

Some Pronounciations C 1 = “C sub one” or “C one”

Some Pronounciations a + b = “a plus b” a – b = “a minus b” a x b = “a times b” a/b = “a over b” a b = “a to the b” a 2 = “a to the second/ a squared” a 3, a 4 = “a to the third, a to the fourth, etc” 0.05 = “zero point zero five” 2x10 -5 = “two times ten to the negative fifth”

Introduction to Magnetic Fields We know that charged objects produce electric fields What are sources of magnetic fields? - permanent magnets - current

Introduction to Magnetic Fields: Permanent Magnets A permanent magnet is made from magnetized material that consistently produces its own magnetic field – this is due to something known as ferromagnetism Ferromagnetic materials can either form permanent magnets, or are attracted to magnets

Introduction to Magnetic Fields: Permanent Magnets A bar magnet is a permanent magnet, and consists of two poles, north and south The magnetic field lines leave from the north pole and enter the south pole

Introduction to Magnetic Fields: Permanent Magnets Opposite poles of a magnet attract each other, and like poles repel

Introduction to Magnetic Fields: Permanent Magnets when you break a magnet in half, you end up with two smaller magnets, both with north and south poles there are no magnetic monopoles

Introduction to Magnetic Fields: Permanent Magnets Magnetic Field of a Bar Magnet

How do we define a magnetic field? In electrostatics, Since magnetic monopoles don’t exist, however, this changes things a bit

How do we define a magnetic field?

= perpendicular projection of onto If, Cross Product Review

How do we define a magnetic field?

Concept Question

Concept Question Solution

Magnetic force on a current-carrying wire

The direction of current is reversed from B, so the wire bends in the opposite direction ABC

Group Problem

Some Notes Homework assignment! Due on Friday, Jan 18th

Concept Question

Charged particle in a magnetic field What happens to the path of a moving charged particle as it enters a magnetic field?

Concept Question

Charged particle in a magnetic field If the particle has a component of velocity parallel to the magnetic field, it will follow a helical path

Group Problem θ

Lorentz Force We know a charged particle in an electric field feels an electric force: We also know a moving charged particle in a magnetic field feels a magnetic force: The total force on a moving charged particle in an electric field and a magnetic field feels is the sum of these forces:

Group Problem

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