Physik LK 7 - Millikan Versuch

Summary

This video explains Millikan's oil drop experiment, which was designed to measure the elementary charge of an electron. It describes the experimental setup, including the oil droplets, the capacitor, and the microscope used to track their movement. The experiment involves measuring the rise and fall of charged droplets in an electric field, where various forces like electric force, gravity, buoyancy, and friction come into play. Through precise calculations based on these forces, Millikan determined that the charge on the droplets is quantized, always appearing as integer multiples of the elementary charge, a groundbreaking discovery in physics.

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Q & A

What is the main goal of the Millikan oil drop experiment?

The main goal of the Millikan oil drop experiment is to determine the elementary electric charge by observing the behavior of charged oil droplets in a capacitor and analyzing the forces acting on them.

What equipment is used in the Millikan oil drop experiment?

The experiment uses a parallel plate capacitor, a light source, a microscope, and an oil spraying device to inject small, charged oil droplets into the capacitor. Additionally, a voltage can be applied across the plates to influence the droplets.

Why are the oil droplets charged in the experiment?

The oil droplets are charged as they are sprayed into the capacitor. This charge is critical for observing their motion under an electric field and calculating the elementary charge.

What forces are acting on the oil droplets during the experiment?

The oil droplets experience several forces: electric force (due to the applied electric field), gravitational force (pulling the droplets downward), buoyancy (the upward force due to displaced air), and friction (air resistance opposing the motion).

How is the charge on the oil droplets calculated?

The charge on the oil droplets is calculated by measuring their constant velocity during their upward and downward movement in the electric field. The forces acting on the droplets are balanced using equations, and from these, the charge can be derived.

What is the significance of the result obtained from the Millikan experiment?

The experiment demonstrated that electric charge is quantized, meaning that the charge on the oil droplets is always a multiple of a fundamental, smallest unit of charge, known as the elementary charge (~1.6 × 10^-19 Coulombs).

What role does the simulation play in this experiment?

The simulation is used to demonstrate the oil drop experiment in a virtual environment, allowing for easy visualization of the oil droplets' motion, as well as the application of voltage and measurement of their speed, which would be difficult to show with physical equipment in the video.

How does the experiment differentiate between rising and falling oil droplets?

The experiment differentiates between rising and falling droplets by measuring the time it takes for the droplets to move in each direction. The velocity is constant during both rise and fall, but the direction of the applied electric field changes, altering the forces acting on the droplets.

What are the mathematical steps used to determine the droplet radius?

The droplet radius is determined by using the force balance equations for both the rising and falling droplets. By subtracting the equations for rising and falling droplets, the radius is derived, and then the droplet's charge can be calculated using the known physical constants.

Why is the elementary charge considered a fundamental constant in physics?

The elementary charge is the smallest possible unit of charge that can exist in isolation. The Millikan experiment confirmed its existence, and this constant is essential in understanding the quantization of charge and forms the basis for much of electrical theory and atomic physics.