What kind of paper was that? Where did you get the speaker? I'm interested in doing this experiment/observation myself.

This is just regular paper & pencil. The speaker is a Piezo buzzer which you can get at radio shack type stores for cheap. Although soon I'll have DIY speakers! (see here for great project: http://www.youtube.com/watch?feature=player_embedded&v=R7zjfaPKMSE)

When he rubbed the line with the wire,why did it make a squeaky sound?

Because the wire was conducting electricity through the speaker, so the more electricity that got through, the more noise it made, the less electricity that got through the less noise it made. As for the line, well the line was graphite, which is a conductor, and as he brought the leads closer or farther apart, more or less electricity could get through.

Brit is using DC so how is the speaker produce sound? A speaker requires the input that is changing with some frequency.

Apparently Brit is using Piezo Buzzer with built-in oscillator, which runs from DC. Its loudness is determined by the DC voltage.

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Physics library

Course: Physics library > Unit 18

Lesson 6: Discovery of resistors

Listen to variable resistance

Name: Listen to variable resistance
Uploaded: 2013-04-26T16:04:11Z
Description: Here we draw a line on a page and use it as a variable resistor in series with a speaker. What relationship do we hear? Does it sound linear?

Google Classroom

Here we draw a line on a page and use it as a variable resistor in series with a speaker. What relationship do we hear? Does it sound linear? Created by Brit Cruise.

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That One Doge
Posted 10 years ago. Direct link to That One Doge's post “What kind of paper was th...”
What kind of paper was that? Where did you get the speaker?
I'm interested in doing this experiment/observation myself.
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(3 votes)
Answer
- brit cruise
  Posted 10 years ago. Direct link to brit cruise's post “This is just regular pape...”
  This is just regular paper & pencil. The speaker is a Piezo buzzer which you can get at radio shack type stores for cheap.
  
  Although soon I'll have DIY speakers! (see here for great project: http://www.youtube.com/watch?feature=player_embedded&v=R7zjfaPKMSE)
  Comment on brit cruise's post “This is just regular pape...”
  (13 votes)
时若斯/anonymous
Posted 8 years ago. Direct link to 时若斯/anonymous's post “When he rubbed the line w...”
When he rubbed the line with the wire,why did it make a squeaky sound?
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(2 votes)
Answer
- Milinium Otaku
  Posted 6 years ago. Direct link to Milinium Otaku's post “Because the wire was cond...”
  Because the wire was conducting electricity through the speaker, so the more electricity that got through, the more noise it made, the less electricity that got through the less noise it made. As for the line, well the line was graphite, which is a conductor, and as he brought the leads closer or farther apart, more or less electricity could get through.
  Button navigates to signup page
  (2 votes)
suniltyagi
Posted 8 years ago. Direct link to suniltyagi's post “Brit is using DC so how i...”
Brit is using DC so how is the speaker produce sound? A speaker requires the input that is changing with some frequency.
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(2 votes)
Answer
- Krzysztof
  Posted 7 years ago. Direct link to Krzysztof's post “Apparently Brit is using ...”
  Apparently Brit is using Piezo Buzzer with built-in oscillator, which runs from DC.
  Its loudness is determined by the DC voltage.
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  (2 votes)
Michael D. Westhuys
Posted 6 years ago. Direct link to Michael D. Westhuys's post “it that quiet and loud or...”
it that quiet and loud or high frequentie and lower frequentie?
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(1 vote)
Answer
Potato Productions
Posted 6 years ago. Direct link to Potato Productions's post “What would happen if you ...”
What would happen if you simply drew a singular line across the page (one stroke across?)
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(1 vote)
Answer
- Milinium Otaku
  Posted 6 years ago. Direct link to Milinium Otaku's post “As you need the graphite ...”
  As you need the graphite to conduct, and I don't believe paper can conduct anything, if you drew one thing singular line, you would probably get very little to no noise at all.
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  (1 vote)
Natalie Gray
Posted 8 years ago. Direct link to Natalie Gray's post “Does the sound come from ...”
Does the sound come from the clip touching the pencil lead I am unclear.?
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(1 vote)
Answer
- Milinium Otaku
  Posted 6 years ago. Direct link to Milinium Otaku's post “No, it comes from the ele...”
  No, it comes from the electricity passing through the speaker.
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  (1 vote)
rosawen2012
Posted 9 years ago. Direct link to rosawen2012's post “what do the sounds mean, ...”
what do the sounds mean, or do they not mean anything?
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(1 vote)
Answer
- Exponentially Radical
  Posted 8 years ago. Direct link to Exponentially Radical's post “Brit was able to adjust t...”
  Brit was able to adjust the sound intensity by changing the location of an electrode. From this we see that he has made a variable resistor, which offers high resistance, low resistance, and a virtually unlimited set of intermediate resistances. Brit showed us how to make a variable resistor. He also helped us to develop intuition for variable resistors. If we curl, spiral, or helix the paper, then we have a compact version of a very long sheet of penciled paper.
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  (1 vote)
Ahmad Raza
Posted 7 years ago. Direct link to Ahmad Raza's post “does current passes throu...”
does current passes through rocks
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(1 vote)
Answer
- APDahlen
  Posted 7 years ago. Direct link to APDahlen's post “Hello Ahmad, Depends on ...”
  Hello Ahmad,
  
  Depends on the rock:
  
  Iron, copper, and lead bearing rocks such as magnetite, hematite, galena, pyrite, chalcopyrite are conductors or at least "semiconductor."
  
  Mica is an example of a good insulator. See https://en.wikipedia.org/wiki/Mica
  
  Regards,
  
  APD
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  (1 vote)
Jude Taha
Posted 5 years ago. Direct link to Jude Taha's post “What would happen if he d...”
What would happen if he drew a circle? When would the sound be high pitched and when will it be low pitched?
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(0 votes)
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Bijoy Kaman
Posted 4 years ago. Direct link to Bijoy Kaman's post “What is variable resistan...”
What is variable resistance
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(0 votes)
Answer

Video transcript

(high pitched tone) (high pitched tone) (high pitched tone) (high pitched tone) (tone goes from quiet to loud) (tone goes from loud to quiet) (tone goes from quiet to loud) (tone goes from loud to quiet) (tone goes back and forth from quiet to loud)