Classical Physics Laser Disk D/44 Van de Graff Generator How I Work

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Classical Physics Laser Disk D/44 Van de Graff
GeneratorHow I Work

• Created for CVCA Physics
• By
• Dick Heckathorn
• 3 March 2K4

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• Using audio track 2/R
• view all of D/44
• and then
• return to frame
• 22682.

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• 22682
• 22683 - 22920

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• Why is it important to know that there is
  negative charge on the electroscope?
• This negative charge is used to identify the
  kind of charge on the rubber belt and the
  rollers.

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• 22921
• 22922 - 23312

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• Describe the charging process that occurs with
  the clear roller and the rubber belt.
• When the clear roller is rubbed with the rubber
  belt, the clear roller becomes positive.
• The rubber belt becomes negative.

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• What evidence do you see that verifies this
  process?
• The rubber roller causes the indicator of the
  negatively charged electroscope to fall slightly
• The rubber belt causes the indicator to rise.

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• What happens to electrons in this process?
• Electrons are rubbed off the roller onto the
  rubber belt.

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• 23313 - 23589

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• Describe the charging process that occurs with
  the white roller and the rubber belt.
• When the white roller is rubbed with the rubber
  belt, the white roller becomes negative.
• The rubber belt became positive.

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• What evidence do you see of this process?
• The rubber belt causes the indicator of the
  negatively charged electroscope to fall slightly.
• The white roller causes the indicator to rise
  slightly.

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• What happens to electrons in this process?
• Electrons are rubbed off the rubber belt and
  onto the white roller.

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• Step through23590-23593

These still frames show how the machine is
assembled.
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• 23594 - 24404

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• What is the function of the lower screen?
• The screen provides lightning rod-like points
  which permit electrons to jump from the ground
  connection to the lower level of the belt.

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• What is the function of the upper screen?
• The screen provides points onto which electrons
  can jump as they are transferred from the rubber
  belt to the metal globe on the top of the machine.

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• 24405 - 24780

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• Estimate the voltage produced by the
• Van de Graaff generator.
• You will need to use the E-field value of 30,000
  V/cm given on the sound track.

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• 1. How far does the spark jump?
• The spark jumps about 1.2 times the discharge
  ball's diameter (see frame 24638).

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• 2. How big is the ball?
• The ball is about 1/2 the height of the man's
  head (see frame 24631).

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• 3. How big is an average mans head?
• An average man's head is about 25 cm high.

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• 4. When will a spark jump through dry air?
• A spark will jump through dry air when the field
  intensity is 30,000 V/cm.

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• 5. What is the potential difference (in volts)?

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