Millikan's Oil Drop Experiment

• Who conducted Millikan's Oil Drop Experiment?

  Millikan and Fletcher

  
• What was the purpose of Millikan's Oil Drop Experiment?

  To determine the value of elementary charge

  
• What is the method used in Millikan's Oil Drop Experiment?

  • Atomised oil drops sprayed into a chamber
  • Oil does not evaporate quickly
  • Drops ionised by X-rays
  • Charge changes from neutral

  
• Why is oil used instead of water in the experiment?

  Because it does not evaporate quickly
• What happens to the oil drops when they are ionised by X-rays?

  They change from neutral to charged
• How do oil drops become positively charged?

  By losing electrons
• How do oil drops become negatively charged?

  By gaining electrons
• What forces act on the charged oil drops in the experiment?

  Electric and gravitational forces
• What is the condition for stationary oil drops in the experiment?

  QV/d = mg
• What does the variable Q represent in the equation QV/d = mg?

  The charge of the oil drop
• What does the variable m represent in the equation QV/d = mg?

  The mass of the oil drop
• What does the variable g represent in the equation QV/d = mg?

  The acceleration due to gravity
• What is Stokes' Law used for in Millikan's Oil Drop Experiment?

  To determine the mass of each oil drop

  
• How do you calculate the charge of an oil drop in the experiment?

  1. Use the equation QV/d = mg
  2. Rearrange to find Q: Q = mgd/V
  3. Substitute known values
• What should you focus on for the exam regarding the stationary oil droplet condition?

  • Understand the equation QV/d = mg
  • Know how to apply it
  • Focus on its derivation