Millikan Oil Drop Experiment Fundamentals
🔬 R.A. Millikan conducted experiments between 1908 and 1917 to precisely measure the charge of the electron.
💧 A fine mist of oil droplets was sprayed; the mass of a droplet was determined by observing its terminal velocity.
⚡️ X-rays ionized gas, causing electrons to adhere to the oil droplets, giving them a negative charge.
⚖️ When suspended, the droplet's weight ($mg$) is perfectly balanced by the electric force ($qE$), allowing Millikan to solve for the charge ($q$).

Calculating Electron Charge and Mass
🔌 The electric force is calculated as the product of the applied electric field ($E$) and the charge on the drop ($q$).
🔢 Millikan found that all droplet charges were whole number multiples of a fundamental charge equal to $-1.60 \times 10^{-19}$ Coulombs (C).
💡 This fundamental unit of charge was concluded to be the charge of the electron.
⚛️ Using the electron charge and the charge-to-mass ratio determined by Thompson, Millikan calculated the electron mass as $9.10 \times 10^{-28}$ grams.

Key Points & Insights
➡️ The experiment successfully determined the elementary charge ($e$), establishing the value as $-1.60 \times 10^{-19}$ C.
➡️ The mass of the electron was derived to be $9.10 \times 10^{-28}$ grams, highlighting its exceedingly small mass.
➡️ The core principle relies on balancing gravitational force (weight) against the electric force applied across parallel charged plates.

📸 Video summarized with SummaryTube.com on Dec 09, 2025, 08:15 UTC