Physics SL
5
Chapters
329
Notes
Theme A - Space, Time & Motion
Theme B - The Particulate Nature Of Matter
Theme C - Wave Behaviour
Theme D - Fields
Theme E - Nuclear & Quantum Physics
Physics SL
Theme D - Fields
Millikan's Method: Revealing Electron's Charge in 1909
665 words
4 mins read
Last edited on 5th Nov 2024
Table of content
Introduction 🚀
- Millikan's experiment (1909): An experiment conducted by Robert A Millikan and Harvey Fletcher to estimate the charge on an electron.
- Recognition: The experiment is mostly attributed to Millikan alone.
- Nobel Prize: Millikan won it in 1923 for this and his work on the photoelectric effect.
Millikan’s method 🖌️
- Step 1 – Introduction of Oil Drops
- Tiny oil drops are sprayed into a chamber.
- These drops become charged either by ionization (X-rays/beta particles) or by friction.
- Visualise it: Think of a mist sprayer!
- One drop is selected and falls through the air, and three forces act on it
- Drag force (due to air resistance)
- Buoyancy force (opposing gravity)
- Gravitational force (pulling the drop down)
- Result: The drop reaches a "terminal speed" (constant speed) since the total force on it is zero. The weight of the drop can be calculated from this speed.
- Step 2 – Charging the Drop:
- The same drop is charged in the chamber.
- An upward electric force (due to applied electric field) stops the drop from falling.
- Fun fact: This is like making the drop "hover" using electricity!
- From the measurements of the drop's weight and the electric force needed to hold it, the charge on the drop is determined.
Millikan’s findings 📖
- Millikan observed that the extra charge on the oil drops was always a whole-number multiple of a basic charge.
- He attributed this basic charge to a single electron's charge.
- Analogy: Imagine having bags filled with identical marbles. By weighing different bags, you can figure out the weight of one marble. E.g., if bags weigh 420g, 840g, 560g, and 1260g, one marble likely weighs 140g.
- After numerous trials, Millikan estimated the elementary charge to be 1.592 ± 0.003 × 10−19 C.
- Today, the electron's charge is defined exactly as 1.602176634 × 10−19 C.
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Physics SL
Theme D - Fields
Millikan's Method: Revealing Electron's Charge in 1909
665 words
4 mins read
Last edited on 5th Nov 2024
Table of content
Introduction 🚀
- Millikan's experiment (1909): An experiment conducted by Robert A Millikan and Harvey Fletcher to estimate the charge on an electron.
- Recognition: The experiment is mostly attributed to Millikan alone.
- Nobel Prize: Millikan won it in 1923 for this and his work on the photoelectric effect.
Millikan’s method 🖌️
- Step 1 – Introduction of Oil Drops
- Tiny oil drops are sprayed into a chamber.
- These drops become charged either by ionization (X-rays/beta particles) or by friction.
- Visualise it: Think of a mist sprayer!
- One drop is selected and falls through the air, and three forces act on it
- Drag force (due to air resistance)
- Buoyancy force (opposing gravity)
- Gravitational force (pulling the drop down)
- Result: The drop reaches a "terminal speed" (constant speed) since the total force on it is zero. The weight of the drop can be calculated from this speed.
- Step 2 – Charging the Drop:
- The same drop is charged in the chamber.
- An upward electric force (due to applied electric field) stops the drop from falling.
- Fun fact: This is like making the drop "hover" using electricity!
- From the measurements of the drop's weight and the electric force needed to hold it, the charge on the drop is determined.
Millikan’s findings 📖
- Millikan observed that the extra charge on the oil drops was always a whole-number multiple of a basic charge.
- He attributed this basic charge to a single electron's charge.
- Analogy: Imagine having bags filled with identical marbles. By weighing different bags, you can figure out the weight of one marble. E.g., if bags weigh 420g, 840g, 560g, and 1260g, one marble likely weighs 140g.
- After numerous trials, Millikan estimated the elementary charge to be 1.592 ± 0.003 × 10−19 C.
- Today, the electron's charge is defined exactly as 1.602176634 × 10−19 C.
Unlock the Full Content!
Dive deeper and gain exclusive access to premium files of Physics SL. Subscribe now and get closer to that 45 🌟
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