WHAT TO DO: Use the different modes and change the frequencies to determine the optimal height of the Coil on the Magnet to produce the best sound.
WHAT TO NOTICE: High frequencies are hard to hear while low frequencies are moving too slowly to make noise. Also, placing the Coil really low on the Magnet does not produce the best sound.
WHAT’S GOING ON: The Magnet has a strong magnetic field coming out of its flat top, which is why the best sound is produced when the coil is hovering just barely over the top of the Magnet.
For this activity each student will need to have a ruler, preferably non-magnetic. Templates for paper rulers are available in the Downloads section. Moving from the Yellow Mode, have the students push the Yellow Button on the Control Panel so that the speaker is in Green Mode.
If you’ve taken a break between this activity and the previous, simply press the Yellow Button 3 times and watch for the Control Panel to glow green. Also, make sure that the slider is all the way to the left. The Green Mode will make the Coil move at much higher frequencies than the Yellow Mode did. Remind the students that frequency is the number of “bounces” per second of the electrified copper Coil when placed on top of the Magnet. When the Slider is moved to the right the Coil will begin to move at higher frequencies that will cause an audible tone (maximum of 2,000 HZ).
As the frequency increases, the Coil begins moving so quickly that the vibrations are no longer visible. At this time, remind the students that the Coil is in fact still in motion, but is now moving so fast that it is creating sound. A short lesson on hearing can be inserted here (range of frequencies humans can hear, range decreases with age, how humans hear etc.)
Show this video for more explanation on how sound waves work.
Now have the students choose to use either their sense of hearing, touch, or sight to determine the optimal height placement of the Coil on the Magnet*. Demonstrate how to flip the Coil over so the yellow base is on top.
TIP: A ruler template can be found and printed for the students to use in the Downloads section.
Students should base their measurements of height between the blue and the yellow bases. The optimal height will make for the loudest noise and/or largest vibrations; these are the things they should be looking for when measuring the optimal height placement of the Coil*. Have the students record this optimal height in their science notebook or the worksheet linked in the Downloads section. Once they have all recorded their measurements you can report them on the board as a class and have a small discussion on what methods they used, why they chose that method, and how they got their measurements. You can then take the average of all of the numbers as a class (small math review) and have the students test the performance at this height.
(*The optimal height is 43mm)
Below is an example spreadsheet that can be used to gather all the results and calculate a class-wide average. It also formats the Method column so you can highlight a discussion on the different approaches to getting measurements.
You can download a version of this spreadsheet in the Downloads Section.
Next Activity: DIY Speaker