What is Millikan oil drop: Definition and 24 Discussions

The oil drop experiment was performed by Robert A. Millikan and Harvey Fletcher in 1909 to measure the elementary electric charge (the charge of the electron). The experiment took place in the Ryerson Physical Laboratory at the University of Chicago. Millikan received the Nobel Prize in Physics in 1923.The experiment entailed observing tiny electrically charged droplets of oil located between two parallel metal surfaces, forming the plates of a capacitor. The plates were oriented horizontally, with one plate above the other. A mist of atomized oil drops was introduced through a small hole in the top plate and was ionized by an x-ray, making them negatively charged. First, with zero applied electric field, the velocity of a falling droplet was measured. At terminal velocity, the drag force equals the gravitational force. As both forces depend on the radius in different ways, the radius of the droplet, and therefore the mass and gravitational force, could be determined (using the known density of the oil). Next, a voltage inducing an electric field was applied between the plates and adjusted until the drops were suspended in mechanical equilibrium, indicating that the electrical force and the gravitational force were in balance. Using the known electric field, Millikan and Fletcher could determine the charge on the oil droplet. By repeating the experiment for many droplets, they confirmed that the charges were all small integer multiples of a certain base value, which was found to be 1.5924(17)×10−19 C, about 0.6% difference from the currently accepted value of 1.602176634×10−19 C. They proposed that this was the magnitude of the negative charge of a single electron.

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  1. guyvsdcsniper

    Calculating Charge of an Electron w/ the Millikan Oil Drop Experiment

    I am doing the Millikan Oil Drop experiment to determine the charge of a single electron. I have been following the lab manual provided by the manufacturer, https://hepweb.ucsd.edu/2dl/pasco/Millikans%20Oil%20Drop%20Manual%20(AP-8210).pdf. The manual defines a simple method to calculate for...
  2. H

    Calculating Velocity in the Millikan Oil Drop Experiment

    Hi, I try to find the velocity for a oil drop. I found the forces. ##F=ma => m\frac{dv}{dt} = \frac{4\pi a^3(\rho - \rho_1)g}{3} - 6\pi n a v## with v on the right side, I don't see how to get the solution. I found the solution on few websites, but without the path to find the solution from...
  3. O

    Millikan Experiment Based Marble Mass Homework

    I arranged the masses in ascending order: 11.0 g 11.1 g 20.6 g 21.4 g 21.5 g 25.7 g 25.8 g 25.9 g 31.6 g 31.9 g I found the average mass of the marbles: 22.65 g I found the difference in masses of the marbles: 0.1 g 9.5 g 0.8 g 0.1 g 4.2 g 0.1 g 0.1 g 5.7 g 0.3 g I found the average of the...
  4. L

    What Are the Results of the Millikan Oil Drop Experiment?

    mass: 1.57x10^-19 kg voltages: 400, 457, 384, 369, 400, 355, 369, 436, 384, 369 distance: 0.1m gravity: 9.81 m/s^2
  5. M

    Find the Mass of the Candy Knowing the Total Mass of the Bags

    [Mentors' note: There's no template because this thread was moved from General Physics. The specification of the problem seems adequate without the template] Hi everyone, I am working through stuff based on the Millikan Oil Drop experiment. There is a question that asks to determine the mass...
  6. S

    Millikan Oil Drop Experiment: Determining Elementary Charge

    Homework Statement Calculate the charge on each oil drop and determine the elementary charge on an electron given the following: Voltage (Attached) d (Distance between two charged plates) = 0.10m m (Of the droplet) = 1.57x10^-15 kg g = 9.8 kgm/s^2 Homework Equations q = mg*d / ΔV The Attempt...
  7. Especial

    Millikan Oil drop lab experiment - equation for speed of drop

    Millikan Oil drop experiment. For my current lab, we are recreating the milian oil drop experiment to measure the charge of an electron. However, we are using 1-micron diameter latex spheres in place of oil drops. Problem: I am having difficulty deriving an equation for the speed of the drop...
  8. J

    Millikan oil drop experiment charge determination

    Howdy y'all! If you could help with the following question, my physics class and I would be extremely grateful. A charged oil droplet is suspended motionless between two parallel plates (d=0.01m) that are held at a potential difference V. Periodically, the charge on the droplet changes as in...
  9. K

    Millikan oil drop experiment

    Homework Statement When Millikan first performed this experiment, he used water droplets instead of oil. He found he could not suspend the droplets; they would start to move up. Why did this happen? Homework Equations N/A The Attempt at a Solution The water droplets would have been so small...
  10. J

    How can I find the smallest positive integer number without dividing q by e?

    I've got mg=kvf, when the e-field is zero, (taking downwards direction as positive), k is some constant and vf is the terminal velocity of an oil drop. Then when the e-field is on, mg+kve=Eq, where Eq is the force from the electric field, and k is the same constant and ve is the drift velocity...
  11. D

    What is the charge of the oil drop in Millikan's experiment?

    Homework Statement When an oil drop falls freely, the velocity first increases, but afterwards it quickly reaches a constant speed, since the air resistance becomes equal to the weight of the oil drop. The air resistance is given by: Fair=6\pir\etav, where \eta is the viscosity of air...
  12. S

    Clarifying the Basics of the Millikan Oil Drop Experiment

    In the Millikan oil drop experiment, was the oil particles positively or negatively charged. and what were the charges of the plates. My textbook and what my gr.10 notes say is that the oil droplets and the bottom plate were positive, but every source online says that they were negative and that...
  13. S

    Can Millikan's Oil Drop Experiment Accurately Measure the Elementary Charge?

    Homework Statement Hi, I had to calculate the charge of an oil drop using a lab simulation Homework Equations q = mgd/v The Attempt at a Solution This is the result i came up with: The charges are not multiple of 1.6x10^-19 C. How can i fix this? Thanks
  14. K

    Millikan Oil Drop Experiment Question

    Homework Statement A 1.50 x 10^-14 kg oil drop accelerates downward at a rate of 1.80 m/s^2 when placed between two horizontal plates that are 9.40 ch apart. The potential difference between the two plates is 980 V. Determine the magnitude of the charge on the oil drop. m = 1.50 x 10^-14 kg...
  15. I

    Millikan Oil Drop Experiment - A few questions

    Millikan Oil Drop Experiment -- A few questions Homework Statement I'm currently doing the millikan oil drop lab; we're using a PASCO Scientific Model 300a (fairly ancient). Specifically, my partner and I are having major problems making any of the droplets in the viewing chamber go back up...
  16. T

    Is It Accurate to Measure the Elementary Charge with Just One Oil Drop?

    I completed the Millikan oil drop lab in class with as much accuracy as possible. I used the PASCO interface and used a very accurate Air pressure calibration. My final experimental charge of the electron derived from the equation in the lab was, 1.8 x 10 ^-19 C. When I turned in my lab, I was...
  17. A

    Why the chamber for the Millikan Oil Drop experiment is so large?

    1. The question asks, why is the external chamber in the Millkan Oil Drop experiment so large? The Millikan Oil Drop is a classic experiment for determing the value of e, fundamental charge, on an electron. In my version of the experiment, I spraw droplets into an external chamber, and then...
  18. B

    What is the charge on the oil drop in Millikan's oil drop experiment?

    Homework Statement A 1.50x10-14 kg oil drop accelerates downwards at a rate of 1.80 m/s2 when placed between two horizontal plates that are 9.40 cm apart. The potential difference between the two plates is 980 V. Determine the magnitude of the charge on the oil drop. Homework Equations...
  19. S

    Millikan oil drop experiment lab help

    Homework Statement I'm doing Millikan's oil drop experiment in a lab. I've got a set of measurements and all that, but in analysis of the data I can't seem to get values for the charges on individual drops that seem reasonable. I find that each drop is carrying between 10 and 300 elementary...
  20. A

    Millikan oil drop experiment potential difference

    Homework Statement in a Millikan oil drop experiment, a uniform electric filed of 1.92 x 10^5 N/C is maintained in a region between two plates separated by 1.5 cm. Find the potential difference between the plates. Homework Equations mg = q x E The Attempt at a Solution in order to...
  21. G

    Millikan Oil Drop Experiment Physics Question

    Homework Statement An oil drop with a mass of 7.20*10^-16kg moves upward at a constant speed of 2.50 m/s between two horizontal, parallel plates. If the electric field strength between these plates is 2.20*10^4 V/m, what is the magnitude of the charge on the oil drop? Homework Equations...
  22. Battlemage!

    Millikan Oil Drop Experiment

    Homework Statement If the charge to mass ratio of a particle, e/m, is known derive a formula to find m, and then by proxy e. Drops of oil are allowed to drop down through a potential difference. With the electric field you can keep a particle suspended for however long you need, droping...
  23. B

    The Millikan Oil Drop Experiment (calculating e given a series of charges)

    Homework Statement This is a lab, where we have to calculate the constant e (1.602e-19 C) by calculating the terminal velocity of an oil drop while under the influence of gravity, and the terminal velocity while under the influence of gravity and a known electric field. Homework...
  24. H

    Millikan Oil Drop Experiment: Solving Homework Equations

    Homework Statement In a Millikan experiment the distance of rise or fall of a droplet is .60 cm and the average time of fall (ie field off) is 21.0 s. With the field turned on, the observed successive rise times are 46.0, 15.5, 28.1, 12.9, 45.3 and 20.0 s a) Prove that charge is quantized...