Magnetism


Class #38

What Causes Magnetism?

Objectives:

  • Understand that when unpaired electrons all have the same spin, an element's magnetic properties increase

Reading:

  • AP2E - Unit 7 - Magnetic Fields

Videos:

Homework:

Zoom Recording Class #38 103020

Note the molecules initially have a random orientation

As time progresses, the molecules orient themselves to the magnetic field, pointing from North to South

Class #39

Magnetic Fields & The Compass

Objectives:

  • Understand that compasses orient themselves be parallel and to point in the positive direction of a magnetic field

  • Understand that the orientation is from North to South, equivalent to the orientation of positive and negative charges. North points to South. Meaning, what we call the earth's North pole is really the South pole!

Reading:

  • AP2E - Unit 7 - Magnetic Fields

Videos:

Homework:

Virtual Lab Demo:

Virtual Lab: Explore Learning Magnetism


Zoom Recording Class #39 110220

Magnetic Fields & Current

Part 1: Existence of Magnetic Fields

Magnetic Induction...an Induced Magnetic Field


Oesrted Experiment

Magnetic Fields & Current

Part 2: Direction & Orientation of the Magnetic Field


The word 'Straight' in the title has more than the usual meaning. The orientation of the magnetic field changes if the wire is curved. Everything we're learning is based on a straight wire.

Magnetic Fields & Current

Part 3: Direction & Orientation of the Magnetic Field in a Plane


The magnetic field is perpendicular to the direction of the current (electron) flow. Since current can flow either direction in a wire, this leads to two possible orientations for this field.

Magnetic fields are denoted with a capital B

Magnetic Fields & Current

Part 4: Magnetic Field Strength


Magnetic Fields & Current

Part 5: Determining the Orientation and Direction of Magnetic Fields

Two 'Right Hand' Rules

One 'Left Hand' Rule


Right Hand Rule #1

How to determine the direction of a magnetic field based on the direction of current flow (or vice versa). This rule is basically universal. Pretty much everyone agrees on this rule.

Right Hand Rule #2

Please note there are multiple options for how to use the 'Right Hand Rule' in electromagnetism. There is NO consistency or definitive agreement on which is best. They all work.

Pay attention to how your college professor wants you to do it.

For me, the last method shown below makes the most sense. I personally like how I use my index finger to point in the direction of current flow, BUT...most people use another method.

Right hand rule for a positive charge moving in a magnetic field. B is the Magnetic Field. V is the direction of motion of the particle. Fm is the Magnetic Force.

The Left Hand Rule

The 'Left Hand' Rule is not even used by some people. Its purpose is to analyze negative charges moving through a magnetic field. For whatever reason, standard analysis of charges moving through a magnetic field is based on positive charges (protons).

Left hand rule for a negative charge moving in a magnetic field. B is the Magnetic Field. V is the direction of motion of the particle. Fm is the Magnetic Force.

An alternative to the left hand rule (that I use) to analyze negative charges moving in a magnetic field is just to turn your right hand upside down. The benefit to this is you don't have to change hands. The downside is I personally find it very inconvenient.

Class #41

The Two Right Hand Rules for Magnetism

Objectives:

  • Understand that there are two Right Hand Rules and an optional Left Hand Rule used in analyzing magnetism

    1. One is used to analyze the force applied to a moving positive charge through a magnetic field

    2. Another is used to determine the magnetic field caused by a current moving through a wire

    3. You can apply an optional Left Hand Rule to analyze the force applied to a moving negative charge

Reading:

Videos:


Homework:

Virtual Lab Demos:

Class #42

Electromagnetic Induction

Objectives:

  • Understand the relationship between a changing magnetic field and current flow.

  • Understand that 'Magnetic Flux' is the strength of a magnetic field in a given area

Reading:

Videos:

Homework:

Virtual Lab: Explore Learning Electromagnetic Induction

Demo Lab:

Phet Faraday's Law


Zoom Recording Class #42 110520