Introduction:
The final lab/activity of the unit uses the hands-on magnet activities to introduce the interactions of electricity and magnetism, electromagnetic induction, electromagnets, speakers, motors and some aspects of sound transmission.

Timing: This lab/activity should take about an hour and a half to complete.

Acknowledgments: Station four of this lab is a variation of an experiment that was demonstrated to me by Jim Hill of the Exploratorium.


Group Size: Small groups
 

Learning Objectives:
The objective of this lab/activity is to introduce the interactions of electricity and magnetism electromagnetic induction, electromagnets, speakers, motors and some aspects of sound transmission.
 

Guiding Question:
How does moving charge interact with magnets?
 

Materials:
Each station requires the following:

  • Station one- magnetic wire, lead wires with alligator clips, two D-cell batteries with holders, one nail, and paper clips.
  • Station two- one meter of magnetic wire, connecting wires with alligator clips, two ring magnets, sandpaper, film canister, tape, stereo, and whatever material you plan to use to build the speaker. Plastic cups, plastic yogurt tops, cardboard boxes, tables, chairs. Really anything could work, but cups are probably the best.
  • Station three- one meter of magnetic wire, connecting wires with alligator clips, two ring magnets, sandpaper, film canister, tape, two D-Cell batteries and holders, two large safety pins, and block of wood. The safety pins should be about 3 to 4 inches in size. The wood block could just be section of a 2” x 4”.
  • Station four- Straws, scissors and the boneshaker. See attachment for construction.

 

Procedures:
Warnings:
1. Make sure the computers, iphones, etc. are put away for this experiment. Magnets and computers don’t mix.
2. If you are using very strong magnets, like neodymium, make sure any student with a pacemaker does not take part.


This lab can be broken up and done separately as well. It takes a lot of time and you need two stereos, so doing the stations on at a time can stretch this over a couple of days.
If you plan to do it in a day, set up each station on its own lab table and have students rotate from station to station. Each one takes about 20 - 25 minutes. Label each table by taping a copy of the corresponding worksheet page to the table. The instructor runs station four (the bone shaker), but it only takes a few moments to do it, so the remainder of the time can be spent assisting the other stations.
You may want to give each student their own coil to use for the entire time instead of having students coiling and un-coiling all the time.

Station one: Nothing all that difficult about this one. Students sometimes forget to sand off the ends if this is their first station.
Station two: The materials used for the diaphragm can be anything, just make sure the coil is taped to it and the magnets are on either side. The speakers don’t sound great buy they work. Double check that your stereo will work with a meter of magnetic wire. The standard resistance of a speaker is 8 ohms. I have never had a problem with stereos and boom-boxes, only with mini players, like ipods.
Station three: To motor takes the most time of the four stations. Not because it is difficult to put together, but the fine tuning takes time. Fine tuning includes: move magnets, adjust coil, safety pin alignment, change direction of coil, start spinning the coil the other way, check connections…. it can go on for ever.
Station four: This station takes the least time. You may want to add more questions to the worksheet. Cut straws in half and put the straw on the dowel as the student comes up. It helps to have the boneshaker high enough that students can stand when they use it.
 

Assessment:
Throughout the four stations of the experiment, students will complete questions based on their experiences and gained knowledge.
 

Answer Key or Rubric:
Station One Closure:
1. What relationship did you discover between number of coils and magnetic field strength?
Direct relationship

2. What relationship did you discover between the number of batteries and magnetic field strength?
Direct relationship

3. Why would a magnetic field that could be turned on and off be useful?
Various answers

Station Two Closure:
1. What purpose do the permanent magnets serve when placed in the current carrying coil of wire?
The server to attract or repel the coil of wires.

2. What are two things you could change about your speaker setup to increase its strength?

Increase the number of coils and/or increase the number of magnets.

Station Three Closure:
1. How could you make the motor turn in the opposite direction?
Change the positive and negative connectors for the battery.

2. What are three ways that the experiment could be modified to give the motor a greater speed?
Increase the number of coils, the number of batteries, and/or the number of magnets.

3. What causes the coil to spin?
As a wire carries current it produces a magnetic field that interacts with the magnets and produces and attraction for half of its rotation. The insulated coating left on one side will block the repulsion that occurs when the coil rotates 180 degrees.

Station Four Closure:
1. What causes the dowel to vibrate?
The coil of wire carries a varying electric current (the music) and it creates a varying magnetic field, which interacts with the permanent magnets.


2. Why do you only hear it when you bite it?
It is vibrating your skull, which vibrates the bones and hairs in your ear, instead of the normal path of sound waves in air vibrating the hair and bones in your ear.

3. What are two techniques to increase the strength of the Bone Shaker?
More coils of wire and/or stronger magnets.

Attachments:

Induction Stations Lesson Plan

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