Becky McCoy

Lesson Title: Magnet Motor Computer Lab Timing: 60 minutes

Target Audience:11th and 12th grade Physics Class

Objectives:Students Will Be Able To:

Make observations of changing magnetic fields and electric current. Discover and draw conclusions regarding the relationship between magnetism and electricity. Draw magnetic fields under different circumstances.

The Teacher Will Be Able To: Assess student understanding and comfort level with material in order to determine pacing. Provide students with a variety of scenarios to observe magnetic fields. Guide students towards understanding the relationship between magnetism and electricity.

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:

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.

Prior Knowledge: Electricity Unit, first three magnetism lessons

Aim: Determine a primary relationship between magnetism and electricity.

Concept Map Vocabulary: n/a

Necessary Preparation:

COPIES “How Do Magnetic Field Affect Electricity?” Worksheet

MATERIALS Computers and projection screen

SET UP

Lesson Plan

Aim: Determine a primary relationship between magnetism and electricity.

Physics Push-Up: Quick Write (5 minutes)In their notebooks, have students spend 5 minutes writing about the following prompt:

Describe a magnetic field. What are its properties and equations? Can you give an example of a magnetic field? What might it mean to have a changing magnetic field?

Activity: Magnet Motor Lab (45 minutes)Materials:

Computer for each student or for every 2 to 3 students. Projection screen with attached computer. “How Do Magnetic Field Affect Electricity?” worksheet

Procedure:

Review the Physics Push-Up prompt. Give students 5 minutes to share with the class or their lab groups what they wrote about. Allow a couple minutes for any questions.

Show the PhET demonstration on the projection screen. Walk through the bar magnet section to give students an idea of what they will be doing.

Hand out the worksheet and have students work to complete it. Ideally, students will work independently or in groups of 2 or 3.

Answers and observations should be recorded directly onto the worksheet.

Activity Summary: Hoover Dam (5 minutes)Show pictures of Hoover Dam and its hydroelectric generator. Specifically discuss how the generator is the same or different from the PhET simulation.

Homework:Have students do research from their textbook and two outside sources to learn more about how hydroelectric generators work. They should then write one page about what they have learned, expanding upon their answer from the “Generator” section on the worksheet.

Exit Strategy:Students pack up their computers and write down the homework assignment.

Extension Activity:Go into more depth about the Hoover Dam. This might be an opportunity to watch a short clip about it:

“New Hoover Dam”: http://www.youtube.com/watch?v=D7_rzojvKdE Any documentary

Assessment:Formative:

Student questions and discussions

Summative: Student answers to worksheet questions

Resources:PhET “Generator” Simulation

Notes & Adaptations: Provide student with the direct link or have the simulation pre-loaded on the computers. Before the transformer and generator sections, have a short discussion about what a transformer and

generator are. Try and find some videos of transformers and generators to give students more concrete examples. Find opportunities to reinforce the right/left hand rule throughout the lesson.

How Do Magnetic Fields Affect Electricity?Use the “Generator” simulation on the Colorado PhET website to complete this worksheet.

Bar Magnet

[In this section of the simulation, you will confirm the properties of a bar magnet and its field with the results from the lab we did at the beginning of the unit]

1. Make sure the field inside and outside of the magnet is turned on. Sketch what the field looks like with field lines inside and outside of the magnet. Remember, the red side of the compass points in the same direction your arrows will. Make sure to label the magnet’s polarity!

2. Click the “Flip Polarity” button and draw the new field lines.

Pickup Coil

[In this section, you’ll explore what happens when magnets and electric circuits interact]

3. Move the magnet around near the coil and bulb, what happens? What is different if you move the magnet around further away from the coil and bulb?

4. Describe the cause and effect in #3 – what is changing and what happens?

5. How does your answer to #3 and #4 change (or not) if you move the coil and bulb instead of the magnet?

Electromagnet

[The electromagnet is like the opposite of the Pickup Coil: the current is induces a magnetic field]

6. If the brightness of the magnetic field symbolizes its strength, how does the strength change when the battery’s voltage changes? What if the terminals are switched?

7. Draw the magnetic field around the coil. The arrows represent the direction of current (same as the simulation).

Transformer

[Similar to the transformers that step up and down the electricity that goes through power lines and into our homes]

8. Using the knowledge you have compiled in questions 1-7, write a few sentences describing how the transformer works.

Generator

[This is a simple generator, similar to one that we will be constructing by the end of this unit]

9. Describe how the generator works. Be sure to focus on the exchanges that occur between different types of energy and changing magnetic fields and electric current.