PHYS 10 - Lecture 20 - Magnetism: Fields and Forces

Описание: In Lecture 20, we begin magnetism by connecting the everyday behavior of magnets to the deeper field-based picture used in physics. The lecture starts with familiar ideas—north and south poles, attraction and repulsion, and the important difference between electricity and magnetism: unlike electric charge, magnetic poles do not appear by themselves as isolated monopoles in the way students often first imagine. From there, the lecture shifts toward the more fundamental viewpoint that magnetic effects are really about fields and the forces those fields exert on moving charges and currents.

The second half builds the conceptual toolkit students need to reason about magnetic forces: the magnetic force on a current-carrying wire, the right-hand rules for direction, demonstrations of magnetic force on an electron beam, and a look at common magnetic field geometries and the units used to measure field strength, especially tesla (and also gauss). The through-line of the lecture is that magnetism is more three-dimensional and direction-sensitive than electrostatics, which is exactly why the right-hand rules matter so much here.

Topics in this lecture:
• Magnetism intro: poles, attraction/repulsion, and why there are no magnetic monopoles in the usual model
• Magnetic force on a current-carrying wire
• Right-hand rules for magnetic-force and field directions
• Magnetic force on moving electrons / electron beam demo
• Magnetic field geometries and field-direction intuition
• Units of magnetic field: tesla and gauss

Textbook (free, online on LibreTexts): https://coaphys.xyz/phys10book
Recommended reading: Chapter 10 — Magnetism

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Lecture 20 of 30-ish in "Physics 10 in 30 Lectures"

0:00:00 - Lecture 20 Intro
0:01:46 - Chapter 10 Overview
0:19:58 - Magnetism Intro
0:39:05 - Magnetic Force on Current-Carrying Wire
0:57:33 - Right-Hand Rules
1:12:10 - Magnetic Force on Electrons
1:20:25 - Magnetic Field Geometries
1:39:42 - Units of Magnetic Fields
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