4.12 - Millikan's Oil Drop Experiment

​4.12 - Millikan's Oil Drop Experiment

• ​The oil drop experiment allowed Millikan to determine the charge on the electron.

• He later used this data to determine the mass of the electron. 

Multiple Choice

Who was the first person to mention atoms in his research?

• Avogadro

• Democritus

• Dalton

• Rutherford

Multiple Choice

Which subatomic particle has a neutral charge?

• Proton

• Neutron

• Electron

Multiple Choice

Which subatomic particle has a positive charge?

• Protons

• Neutrons

• Electrons

Multiple Choice

If two positively charged objects move towards each other they will-

• attract

• repel

• remain the same

Multiple Choice

Which subatomic particle has a negative charge?

• Protons

• Neutrons

• Electrons

Multiple Choice

Electric flow is caused by the movement of-

• Protons

• Neutrons

• Electrons

Multiple Choice

Who determined that electrons cause the flow of electricity as they are attracted to the cathode?

• Ben Franklin

• JJ Thompson

• Rutherford

• Milliken

Multiple Choice

The Cathode Ray tube determined-

• there are positive and negative charges

• the flow of electrons towards a positive plate causes electricity to flow

• the mass of the electron

• the charge of the electron

​The man who measured properties of the electron was Robert Millikan (1868-1953). He taught himself physics while a student at Oberlin College in Ohio since there was nobody on the faculty to instruct him in this field.  Millikan completed postgraduate research training in the U.S. and in Germany.  His studies on the properties of the electron proved to be of great value in many areas of physics and chemistry.

​Charge & Mass of the Electon

​Oil Drop Experiment

​Millikan carried out a series of experiments between 1908 and 1917 that allowed him to determine the charge of a single electron, famously know as the oil drop experiment.

He sprayed tiny drops of oil into a chamber. In his first experiment, he simply measured how fast the drops fell under the force of gravity.  He could then calculate the mass of the individual drops.

​Then he sprayed oil drops and applied an electrical charge to them by shining X-rays up through the bottom of the apparatus.  The X-rays ionized the air, causing electrons to attach to the oil drops. The oil drops picked up static charge and were suspended between two charged plates. Millikan was able to observe the motion of the oil drops with a microscope and found that the drops lined up in a specific way between the plates, based on the number of electric charges they had acquired.

​By adjusting the voltage between the plates, Millikan could balance the gravitational force pulling the droplets down with the electric force pulling them up, enabling him to calculate the charge on each droplet, which was always a multiple of a fundamental unit, the charge of an electron.

• ​Millikan used the information to calculate the charge of an electron. He determined the charge to be 1.5924 × 10^-19 C, where C stands for coulomb, which is one ampere*second.

• Today the accepted value of the charge of an electron is 1.602176487 × 10^-19 C. Millikan's experimental value proved very accurate; it is within 1% of the currently accepted value.

• Millikan later used the information from his oil drop experiment to calculate the mass of an electron. The accepted value today is 9.10938215 ×10^-31 kg.

• The incredibly small mass of the electron was found to be about 1/1840 the mass of a hydrogen atom.

Multiple Choice

Which particle is responsible for creating ions?

• Protons

• Neutrons

• Electrons

Multiple Choice

Who measured the charge of the electron?

• Ben Franklin

• JJ Thompson

• Rutherford

• Millikan

Multiple Choice

The electron in the cathode ray experiment was attracted to the cathode plate, meaning that the cathode plate must be ....

• Positively charged

• Negatively charged

• Neutral

Multiple Choice

The Oil Drop Experiment determined ....

• there are positive and negative charges

• the flow of electrons towards a positive plate causes electricity to flow

• the mass of the electron

• the charge of the electron

Multiple Choice

Millikan's Oil Drop Experiment uses which forces?

• Attractive Electrostatic force and Attractive Gravitational Force

• Repulsive Electrostatic force and Attractive Gravitational Force

• Repulsive Electrostatic force and Repulsive Gravitational Force

• Attractive Electrostatic force and Repulsive Gravitational Force

Multiple Choice

The charged particle in the oil drop experiment was deflected from the negative plate, meaning that the oil drop must be ....

• Positively charged

• Negatively charged

• Neutral

Multiple Choice

Who had the first 4 part atomic theory about combining atoms in 1808?

• Heisenburg
• Rutherford 
• Dalton
• Bohr

Multiple Choice

Who discovered the electron's charge by using the oil drop experiment?

• Millikan

• Bohr
• Debrogile
• Thomson

Multiple Choice

Who discovered the electron (NOT its charge) using the cathode ray tube?

• Thomson

• Millikan

• Heisenberg
• Dalton

Multiple Choice

Dalton used the solid sphere model.

• True
• False

Multiple Choice

Around what time did Democritus propose the existence of the indivisible atom?

• 1000 B.C.
• 400 B.C.
• 1919
• 1543