In 1897, JJ Thomson had determined the charge to mass ratio nof the electron. Neither the charge, nor the mass was known at the time
Robert Millikan set out to design and conduct an experiment, to determine the discrete nature of electrical charge. In his famous oil drop experiment showed that charge is discreet, and that its value could be determined. As a result of his work he was able to also determine mass of the electron.
Robert Millikan set out to design and conduct an experiment, to determine the discrete nature of electrical charge. In his famous oil drop experiment showed that charge is discreet, and that its value could be determined. As a result of his work he was able to also determine mass of the electron.
Interactive
Here is a simple yet instructive interactive for Millikan's experiment, from Physics Aviary
Best process is
1. Record both voltage and radius of oil droplet in a spreadsheet
2. For each droplet, determine the mass by calculating the volume and using the supplied density
3. Work out the charge for each by equating the two forces (electric field and gravitational field) (You will have to determine the electric field from the voltage)
4. Carefully examine the charge values - they are multiples of a set value
Here is a simple yet instructive interactive for Millikan's experiment, from Physics Aviary
Best process is
1. Record both voltage and radius of oil droplet in a spreadsheet
2. For each droplet, determine the mass by calculating the volume and using the supplied density
3. Work out the charge for each by equating the two forces (electric field and gravitational field) (You will have to determine the electric field from the voltage)
4. Carefully examine the charge values - they are multiples of a set value
This activity allows students to simulate a simplified version of Robert Millikan's Oil-Drop experiment. Instructions are given under the simulation. By Tom Walsh
