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The ratio for electric charge to the mass of an electron is a fundamental concept in physics and useful for future students interested in the study of physics. From this you can conclude how the electron is hardly affected by gravity and how the electric field governs how the electron behaves. This is important to know for the reason that it is one of the most important values in quantum mechanics. We did this by means of observing the trajectory of electrons in a known constant magnetic field. From this you can find the ratio of electric charge to mass for an electron as a function of observed radii, magnetic field, and energy. This can be done with an electron gun a Helmholtz Coil and a couple of power sources. With all these things we can determine how a beam of electrons curves within a magnetic field and thus measure a radius and with some tricky manipulation figure the ratio for electric charge compared to mass for the electrons. From my experimental data we found that the ratio of e/m is 2.3+/-.23*10 coul/kg. This was one standard deviation away from the accepted value. There was still some systematic and random error that was prevalent throughout the experiment. We will discuss the reasons and sources of these errors. | The ratio for electric charge to the mass of an electron is a fundamental concept in physics and useful for future students interested in the study of physics. From this you can conclude how the electron is hardly affected by gravity and how the electric field governs how the electron behaves. This is important to know for the reason that it is one of the most important values in quantum mechanics. We did this by means of observing the trajectory of electrons in a known constant magnetic field. From this you can find the ratio of electric charge to mass for an electron as a function of observed radii, magnetic field, and energy. This can be done with an electron gun a Helmholtz Coil and a couple of power sources. With all these things we can determine how a beam of electrons curves within a magnetic field and thus measure a radius and with some tricky manipulation figure the ratio for electric charge compared to mass for the electrons. From my experimental data we found that the ratio of e/m is 2.3+/-.23*10 coul/kg. This was one standard deviation away from the accepted value. There was still some systematic and random error that was prevalent throughout the experiment. We will discuss the reasons and sources of these errors. | ||
==<center>Introduction</center>== | ==<center>Introduction</center>== | ||
The charge of an electron is one of the most basic concepts in the entire study of electromagnetism and atomic particles. The | The charge of an electron is one of the most basic concepts in the entire study of electromagnetism and atomic particles. The first person o find an electron was J.J. Thompson. He did so in a series of experiments which used cathode ray tubes to try to find electrons. He did three such different experiments and it wasn't until the third that he found the charge to mass ratio for the electron which he found in 1987<small><sup>2</sup></small>. These results let him to formulate his "Plum Pudding Model" of the atom. This experiment is a lot like the one detailed here. For these experiments he was awarded the Nobel Prize in Physics in the year 1906. | ||
After Thompson did these experiments R.A. Millikan came around and found through experimentation the charge of the electron. His experiments which involve dropping oil droplets in a chamber that could be charged to see how the oil droplets reacted in an electric field. These experiments then lead to the charge that an electron has on it<small><sup>3</sup></small>. He was later awarded the Nobel Prize in Physics for these experiments in 1923 after some controversy due to the deeds of one Felix Ehrenhaft's claim that he found a smaller charge than Millikan, but these claims turned out to be wrong and the prize was given to Millikan. | |||
After Thompson did these experiments R.A. Millikan came around and found through experimentation the charge of the electron. His experiments which involve dropping oil droplets in a chamber that could be charged to see how the oil droplets reacted in an electric field. These experiments then lead to the charge that an electron has on it. He was later awarded the Nobel Prize in Physics for these experiments in 1923 after some controversy due to the deeds of one Felix Ehrenhaft's claim that he found a smaller charge than Millikan, but these claims turned out to be wrong and the prize was given to Millikan. | |||
With out these fundamental experiments we could have not found the charge of the electron, and with out this fundamental constant we could not have been able to do some of the work in chemistry atomic physics and quantum mechanics. The experiment that i did was similar to the experiment that Thompson did in that I am using an electron gun to "boil" off electrons and measure how they behave in a magnetic field. I will vary the force of the electrons by mean of changing the voltage to the electron gun which is the Lorenz Force<small><sup>4</sup></small>, I will also vary the magnetic field by means of changing the current that is applied to the Helmholtz Coils<small><sup>5</sup></small> to show how an electron responds to a changing electric field and or a changing force. | With out these fundamental experiments we could have not found the charge of the electron, and with out this fundamental constant we could not have been able to do some of the work in chemistry atomic physics and quantum mechanics. The experiment that i did was similar to the experiment that Thompson did in that I am using an electron gun to "boil" off electrons and measure how they behave in a magnetic field. I will vary the force of the electrons by mean of changing the voltage to the electron gun which is the Lorenz Force<small><sup>4</sup></small>, I will also vary the magnetic field by means of changing the current that is applied to the Helmholtz Coils<small><sup>5</sup></small> to show how an electron responds to a changing electric field and or a changing force. | ||
Revision as of 21:12, 8 December 2009
Experimental Determination of the Electron Charge to Mass Ratio
Abstract
The ratio for electric charge to the mass of an electron is a fundamental concept in physics and useful for future students interested in the study of physics. From this you can conclude how the electron is hardly affected by gravity and how the electric field governs how the electron behaves. This is important to know for the reason that it is one of the most important values in quantum mechanics. We did this by means of observing the trajectory of electrons in a known constant magnetic field. From this you can find the ratio of electric charge to mass for an electron as a function of observed radii, magnetic field, and energy. This can be done with an electron gun a Helmholtz Coil and a couple of power sources. With all these things we can determine how a beam of electrons curves within a magnetic field and thus measure a radius and with some tricky manipulation figure the ratio for electric charge compared to mass for the electrons. From my experimental data we found that the ratio of e/m is 2.3+/-.23*10 coul/kg. This was one standard deviation away from the accepted value. There was still some systematic and random error that was prevalent throughout the experiment. We will discuss the reasons and sources of these errors.
Introduction
The charge of an electron is one of the most basic concepts in the entire study of electromagnetism and atomic particles. The first person o find an electron was J.J. Thompson. He did so in a series of experiments which used cathode ray tubes to try to find electrons. He did three such different experiments and it wasn't until the third that he found the charge to mass ratio for the electron which he found in 19872. These results let him to formulate his "Plum Pudding Model" of the atom. This experiment is a lot like the one detailed here. For these experiments he was awarded the Nobel Prize in Physics in the year 1906.
After Thompson did these experiments R.A. Millikan came around and found through experimentation the charge of the electron. His experiments which involve dropping oil droplets in a chamber that could be charged to see how the oil droplets reacted in an electric field. These experiments then lead to the charge that an electron has on it3. He was later awarded the Nobel Prize in Physics for these experiments in 1923 after some controversy due to the deeds of one Felix Ehrenhaft's claim that he found a smaller charge than Millikan, but these claims turned out to be wrong and the prize was given to Millikan.
With out these fundamental experiments we could have not found the charge of the electron, and with out this fundamental constant we could not have been able to do some of the work in chemistry atomic physics and quantum mechanics. The experiment that i did was similar to the experiment that Thompson did in that I am using an electron gun to "boil" off electrons and measure how they behave in a magnetic field. I will vary the force of the electrons by mean of changing the voltage to the electron gun which is the Lorenz Force4, I will also vary the magnetic field by means of changing the current that is applied to the Helmholtz Coils5 to show how an electron responds to a changing electric field and or a changing force.
References
2. J. Thompson, "Cathode Rays". The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, Fifth Series, 296 (1897)
3.R. A. Millikan, "On the elementary electrical charge and the Avogadro constant". The Physical Review, Series II 2: 109–143 (1913).
4.Lorenz Force [1]
5.R. Merritt, C. Purcell, and G. Stroink. "Uniform magnetic field produced by three, four, and five square coils". Review of scientific Instruments, Volume 54, Issue 7, 879 (1983).
6.R.C. Gibbs and R.C. Williams, "The Electronic Atomic Weight and e/m Ratio". The Physical Review, Volume 44, Issue 12, 1029 (1933).
