Becky McCoy

Lesson Title: Magnetic Fields 2 Timing: 60 minutes

Becky McCoy

Becky McCoy

Target Audience:11th and 12th grade Physics course

Objectives:Students Will Be Able To:

Observe magnetism and electricity interacting. Make predictions as to the relationship between electricity and magnetism. Describe magnetic situations using the hand rules.

The Teacher Will Be Able To: Demonstrate magnetism and electricity interacting. Scaffold students’ understanding of how magnetism and electricity relate.

Standards Assessed: New York State Standards in Physics

4.1 Observe and describe transmission of various forms of energy. xv. map the magnetic field of a permanent magnet, indicating the direction of the field between

the N (north-seeking) and S (south-seeking) poles 4.1j Energy may be stored in electric* or magnetic fields. This energy may be transferred

through conductors or space and may be converted to other forms of energy.4.1k Moving electric charges produce magnetic fields. The relative motion between a conductor

and a magnetic field may produce a potential difference in the conductor.5.1 Students can explain and predict different patterns of motion of objects (e.g., linear and uniform

circular motion, velocity and acceleration, momentum and inertia). 5.1t Gravitational forces are only attractive, whereas electrical and magnetic forces can be

attractive or repulsive.

National Science Education Standards (1996) as published on http://www.nap.edu6.2 Table of Physical Science Standards, Level 9-12

Structure and properties of matter. Interactions of energy and matter.

6.7 Table of History and Nature of Science Standards, Level 9-12 Science as a human endeavor. Historical perspectives.

Misconception(s) Addressed:

Becky McCoy

Magnetic fields behave the same as electric fields

North and south magnetic poles are the same as positive and negative charges.

Magnetic field lines start at one pole and end at the other.

Poles can be isolated. Flux is the same as field lines. Flux is actually the flow of the

magnetic field. Magnetic fields are the same as

electric fields. Charges at rest can experience

magnetic forces.

Magnetic fields from magnets are not caused by moving charges.

Magnetic fields are not 3-dimensional.

Magnetic field lines hold you on the Earth.

Charges, when released, will move toward the poles of a magnet.

Generating electricity requires no work.

When generating electricity only the magnet can move.

Voltage can only be induced in a closed circuit.

Magnetic flux, rather than change of magnetic flux, causes an induced emf.

Becky McCoy

Prior Knowledge: Electricity Unit and Lessons 1-2 of Magnetism Unit

Aim: Use hand rules to describe magnetic fields.

Concept Map Vocabulary: n/a

Necessary Preparation:COPIES

MATERIALS Computer/projector MIT hand rule examples (on paper or projected)

SET UP

Becky McCoy

Lesson Plan

Aim: Use hand rules to describe magnetic fields.

Physics Push-Up: Free Write (5 minutes)Have the students answer the following questions:

What affects the direction of a magnet field? What affects the strength of a magnet field? Where do magnetic fields exist? What type of connection might exist between magnetic fields and electricity?

Activity: Hand Rules and Crazy Videos (33 minutes)Materials:

Computer with projector

Procedure:

Begin class with a quick review from last period: What shapes did the iron filings create with a single magnet? Two magnets? How does this relate to the magnetic field of the Earth?

Review the homework questions as a large class or in lab groups.

“Now we are going to explore how you can create magnetic fields using electricity. First, let’s look at some demonstrations of how magnets and electricity might interact.”

As students watch each of the following videos (or demonstrations if you are able to do them), have them predict what is happening in the video.

Two wires: http://www.youtube.com/watch?v=43AeuDvWc0k&feature=related Lorentz Force on single wire: http://www.youtube.com/watch?v=_X8jKqZVwoI&feature=related Solenoid Electromagnet: http://www.youtube.com/watch?v=g9d3GOXnDm8&feature=related Eddy Current: http://www.flickr.com/photos/kgigante/3513045264/

“We can figure out which direction the magnetic field, current, and forces face by using the ‘Right and Left Hand Rules’.”

Write on the board: Right = pRoton and Left = eLectron

“This means the rules for protons can be illustrated by your right hand and for electrons by your left hand. The Left Hand Rule is more useful since we study the movement of electrons, but many older textbooks and college courses only use the Right Hand Rule, so I want you to be familiar with it.”

Becky McCoy

Have everyone stick their right hand out in front as if they are going to shake someone’s hand. Everyone’s fingers should be extended and thumbs should be outstretched in a perpendicular direction, you can then explain:

THUMB = direction of velocity/current FINGERS = direction of magnetic field THUMB = forceHave students write this in their notes (maybe with some drawings) and confirm the predictions from each of the videos.

“We can connect these hand rules to the force equation from yesterday since they both show that the force, the magnetic field, and the current/velocity of a charge are all perpendicular to each other.”

Activity Summary: Hand Rule practice (15 minutes)Have students do some practice problems from the MIT website.

Resources: Pictures: http://physicsed.buffalostate.edu/SeatExpts/resource/rhr/rhr.htm Examples: “Practice Right Hand Rule #1” from http://ocw.mit.edu

Homework: Video Review (5 minutes)Students should re-watch the videos from class and analyze the demonstrations using the right/left hand rule to confirm the phenomena occurring. If there is no way to post the videos online, hand out a half sheet with the URL for each video.

Exit Strategy: (2 minutes)Before students leave the room, they must explain the hand rules to their partner and which hand goes with which charge.

Extension Activity:Have students begin or complete homework in class.

Assessment: Student discussions and questions. Student responses to hand rule examples.

Resources: Pictures: http://physicsed.buffalostate.edu/SeatExpts/resource/rhr/rhr.htm Examples: “Practice Right Hand Rule #1” from http://ocw.mit.edu Two wires: http://www.youtube.com/watch?v=43AeuDvWc0k&feature=related Lorentz Force on single wire: http://www.youtube.com/watch?v=_X8jKqZVwoI&feature=related Solenoid Electromagnet: http://www.youtube.com/watch?v=g9d3GOXnDm8&feature=related Eddy Current: http://www.flickr.com/photos/kgigante/3513045264/

Notes & Adaptations: