Introduction to Magnetism

This lesson on magnetism is presented without accompanying videos, focusing solely on the available materials and assignments related to the topic.

Cosmos extra credit assignments:
- Students are encouraged to complete these assignments as early as possible for better learning outcomes.
- The instructor prefers to grade these assignments personally, noting they provide interesting insights into student interpretations.
Upcoming assignments:
- Lab 4 is scheduled for Wednesday of the next week, focusing on RC circuits, which will be part of the exam preparation.
- New sensors and software will be utilized in the lab, requiring students to complete the Vernier analysis tutorial beforehand to ensure proficiency in lab procedures.
- Other ongoing assignments, including spot checks 4 and 5, and extra TA assignments 6 and 7, are due soon. Students should plan their schedules to meet these deadlines and communicate potential issues with the instructor.

The instructor humorously mentions pets, showcasing photographs of their cat, Remus, and dog, Tilly, who have a love-hate relationship.

Magnetism has historical roots, with lodestones (magnetite) noted for their iron-attracting properties by ancient Greeks.
Lodestone: The term originates from Middle English, meaning "way stone"—a tool for navigation, crucial for early explorers.
Prior to 1830, magnetism was regarded as distinct from electricity until James Clerk Maxwell unified these concepts through his equations.

James Clerk Maxwell: Established that magnetism and electricity are interconnected through his equations, known as Maxwell’s equations.
- Originally wrote 16 equations, which were later simplified by Oliver Heaviside to four.
- Heaviside's work laid the foundation for modern electromagnetism and vector calculus.
Ether Theory vs. Reality: Early science viewed electromagnetism as separate entities which was ultimately unified by Maxwell.

Fundamental Principle: Moving charges create magnetic fields.
- A charged particle in motion around another charged particle creates a magnetic field around it, leading to various interactions.
Magnetic Poles: All magnets have a north and a south pole; these poles can never exist independently (monopoles do not exist).
- The magnetic field lines are continuous loops, illustrating that magnetic field lines can never begin or end, differing from electric field lines.

Measurement of Magnetic Fields: Magnetic fields are experimented on using iron filings, which align with the field, illustrating magnetic lines of force.
Gauss’s Law for Magnetism states no magnetic monopoles exist, which helps define the behavior of magnetic fields mathematically.

Compasses: A compass needle aligns with Earth's magnetic field, pointing towards magnetic north (the south magnetic pole is located in the northern hemisphere).
Types of Materials and Their Magnetic Properties:
- Ferromagnetic Materials: Strongly magnetizable (iron, nickel, cobalt) and can be permanently magnetized.
- Paramagnetic Materials: Weakly magnetizable; they align in the same direction as an external field but do not retain magnetism.
- Diamagnetic Materials: Exhibit a weak, negative response to magnetic fields and repel them (e.g., bismuth, copper).

Electrons possess a property called spin, contributing to their magnetic moments. Spin can be visualized metaphorically with the rotation of playing cards.
At the atomic level, a spinning electron creates a magnetic field, which contributes to the properties of magnetic materials.

Electromagnetism: Defined by moving charges creating magnetic fields. An electromagnet can be created by winding wire around a core and allowing current to flow, which generates a magnetic field stronger than a permanent magnet.
Magnetic field strength is measureable in Tesla (with Gauss as a smaller unit), and specific scientific principles govern their interactions with charge and motion.

The Lorentz force describes how magnetic fields exert forces on moving charges. The formula is: $F = q(v \times B)$
- Where F is the magnetic force, q is the charge, v is the velocity of the charge, and B is the magnetic field.