Elementary Charge

Bozeman Science
19 May 201404:50
EducationalLearning
32 Likes 10 Comments

TLDRIn this AP Physics essentials video, Mr. Andersen explains the concept of elementary charge, the smallest unit of electric charge an object can possess. Highlighting the Millikan oil drop experiment, he describes how the charge is quantized, with a value of 1.6 times 10 to the negative 19th Coulombs, and can only be a multiple of this value. Protons and electrons exhibit this charge, with protons being positively charged and electrons negatively charged. The video emphasizes the importance of understanding charge quantization in atomic structure and the impossibility of having a charge smaller than the elementary charge.

Takeaways
  • 🔋 The concept of 'elementary charge' refers to the smallest unit of electric charge an object can have.
  • 🧪 Robert Millikan determined the value of the elementary charge through his oil drop experiment.
  • 💧 The experiment involved observing oil drops in an electromagnetic field and adjusting voltage to make them hover.
  • ⚖️ The charge was found to be quantized, meaning it can only be an integer multiple of the elementary charge (1.6 x 10^-19 Coulombs).
  • 🔄 Charges are never in between these quantized values; they can be positive or negative but not fractional.
  • 🥰 Protons and electrons both have an elementary charge, though protons are much more massive.
  • 🔬 Millikan's setup included an atomizer for oil droplets, a microscope for observation, and charged plates to control the drops' motion.
  • 🌬️ Factors affecting the oil drops' motion included gravity, air resistance, and electromagnetic forces.
  • 🎯 By balancing the gravitational and electromagnetic forces, Millikan could measure the voltage and calculate the elementary charge.
  • 🤔 The existence of fractional charges is not possible due to the quantized nature of electric charge.
  • 🌀 Quarks, which make up protons and neutrons, have partial charges that sum up to an integer multiple of the elementary charge when combined.
Q & A

  • What is the elementary charge?

    -The elementary charge is the smallest unit of electric charge that an object can have, determined to be 1.6 times 10 to the negative 19th Coulombs.

  • Who determined the value of the elementary charge?

    -Robert Millikan determined the value of the elementary charge through his oil drop experiment.

  • What was the basic setup of Millikan's oil drop experiment?

    -The setup included an atomizer to produce oil drops, a microscope to observe the drops, and two charged plates to apply voltage and control the motion of the oil drops.

  • How did Millikan measure the charge on the oil drops?

    -Millikan adjusted the voltage applied to the charged plates to balance the gravitational pull on the oil drops, allowing him to measure the voltage and calculate the charge.

  • What does it mean for electric charge to be quantized?

    -Quantized electric charge means that charges are always whole numbers or multiples of the elementary charge, and there are no fractions or decimals of this charge.

  • What are the possible values for the elementary charge?

    -The elementary charge can be zero (no charge), a positive multiple of the elementary charge, or a negative multiple of the elementary charge.

  • How does the concept of charge quantization relate to subatomic particles like quarks?

    -Although quarks have fractional charges, they do not exist independently but are always found in combinations that result in whole numbers of the elementary charge.

  • What are the three fundamental particles that make up an atom?

    -An atom is made up of protons, neutrons, and electrons.

  • What is the charge of a proton?

    -A proton has a positive elementary charge (+e).

  • What is the charge of an electron?

    -An electron has a negative elementary charge (-e).

  • What is the significance of the value of the elementary charge in physics?

    -The value of the elementary charge is fundamental to understanding the quantization of electric charge and the behavior of charged particles in various physical contexts.

  • How accurate was Millikan's determination of the elementary charge compared to modern values?

    -Millikan's determination of the elementary charge was within one percent of the modern accepted value, which is an impressive level of accuracy for the time.

Outlines
00:00
🔬 Introduction to Elementary Charge

This paragraph introduces the concept of elementary charge, which is the smallest unit of electric charge an object can have. It explains that this charge was determined by Robert Millikan through his oil drop experiment. The main point is that charges are quantized, meaning they can only be whole numbers multiples of the elementary charge, which is 1.6 x 10^-19 Coulombs. The paragraph also touches on the fact that despite differences in mass, protons and electrons have the same magnitude of charge.

Mindmap
Keywords
💡Elementary Charge
The elementary charge refers to the smallest unit of electric charge that an object can have, which is quantized and cannot be divided into smaller parts. In the video, it is explained that this charge is either a positive or negative multiple of a fundamental value, 1.6 times 10 to the negative 19th Coulombs, and is the basis for understanding the charge of particles like protons and electrons.
💡Millikan Oil Drop Experiment
The Millikan oil drop experiment is a historical scientific experiment conducted by Robert Millikan to measure the elementary charge and to demonstrate the quantization of electric charge. In the video, it is described how Millikan used oil drops in an electromagnetic field to determine the charge of an electron, leading to the discovery of the elementary charge.
💡Quantization
Quantization, in the context of electric charge, refers to the property that charge can only exist in discrete amounts, specifically in integer multiples of the elementary charge. The video emphasizes that electric charge cannot exist in fractions or between multiples of the elementary charge, indicating a fundamental aspect of the behavior of electric charges in physics.
💡Electric Charge
Electric charge is a fundamental property of matter that gives rise to one of the four fundamental forces of nature, the electromagnetic force. In the video, electric charge is discussed in relation to its quantization and the role it plays in the structure of atoms, with protons having a positive charge and electrons having a negative charge.
💡Robert Millikan
Robert Millikan was an American physicist who is known for his oil drop experiment, which allowed him to measure the charge of the electron and establish the value of the elementary charge. In the video, Millikan's contribution to physics is highlighted through the explanation of his experiment and its significance in understanding electric charge.
💡Charged Particles
Charged particles are particles that possess an electric charge, either positive or negative. In the context of the video, charged particles such as electrons and protons are fundamental components of atoms, with their charges being quantized in units of the elementary charge.
💡Viscosity
Viscosity is a measure of a fluid's resistance to flow or its internal resistance to deformation at a given rate. In the video, air viscosity is mentioned as a factor that affects the falling speed of the oil drops in Millikan's experiment, alongside the gravitational pull and the electromagnetic force.
💡Electromagnetic Field
An electromagnetic field is a field produced by electrically charged objects or moving electric charges. In the video, the electromagnetic field is used by Millikan to manipulate the motion of the oil drops, allowing him to measure the charge on the drops by adjusting the voltage applied to the charged plates.
💡X-Ray Tube
An X-ray tube is a device used to generate X-rays, which are a form of electromagnetic radiation with high energy and frequency. In the video, the X-ray tube is used in Millikan's experiment to ionize the air and cause the oil drops to become charged by knocking electrons off or adding electrons to the drops.
💡Gravitational Force
Gravitational force is the attractive force that acts between all masses, causing them to pull towards each other. In the video, gravitational force is one of the forces acting on the oil drops in Millikan's experiment, pulling them downward as they fall through the air.
💡Atom
An atom is the smallest unit of a chemical element that retains the properties of that element, consisting of protons, neutrons, and electrons. In the video, the structure of an atom is discussed in relation to the charges of its constituent particles, with protons in the nucleus carrying a positive charge and electrons outside carrying a negative charge.
Highlights

The concept of elementary charge, the smallest unit of electric charge an object can have.

The determination of the elementary charge by Robert Millikan through the oil drop experiment.

The method of dropping oil through a hole and using a microscope to observe the oil drops under varying voltages.

The discovery that charge is quantized, meaning it can only be a multiple of the elementary charge or none at all.

The quantization of charge implies that it is always a whole number multiple of the elementary charge (1.6 x 10^-19 Coulombs).

The role of electric charge in particles like protons and electrons, both having charges but of opposite signs.

The Millikan oil drop experiment setup, including an atomizer, microscope, charged plates, and an x-ray tube.

The balance of gravitational force, air resistance, and electromagnetic force on the oil drops.

The use of x-rays to ionize the air and oil drops, which was a key aspect of the experiment.

Millikan's ability to regulate voltage to balance the forces on the oil drops and measure the resulting elementary charge.

The calculated value of the elementary charge as 1.6 x 10^-19 Coulombs, with an accuracy within 1% of the modern value.

The impossibility of having a charge smaller than the elementary charge, reinforcing the concept of charge quantization.

The composition of an atom with protons, neutrons, and electrons, each having distinct charges and masses.

The quarks within protons and neutrons having fractional charges that sum up to an integer multiple of the elementary charge.

The significance of the oil drop experiment in confirming the quantization of electric charge.

Transcripts

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Elementary ChargeMillikan ExperimentQuantizationPhysics EducationElectric ChargeProtons vs ElectronsCharge ConservationScientific DiscoveryAP PhysicsEducational Video