In this experiment, you will measure em, the ratio of the electrons charge e to its mass m. Thomson in 1897 at the cavendish laboratory in cambridge, england. This lab consists of two parts using one electron gun. P31220 lab 1 charge to mass ratio of the electron purpose. The nominal value for the apparatus you will be using is 1. The quantity representing the ratio of an electrons charge to its mass was experimentally sought after for the first time by j. Hydrogendetermine e simplest of atomic, th systems, has an emission spectrum which is consistent with an elementary theory derived from.
Measuring separately the electric charge \e\ and the rest mass \m\ of an electron is a difficult task because both quantities are extremely small \e\ 1. They are the two notable isotopes of hydrogen atom. The negative terminal of the 500 v supply, the positive terminal of. Physics 19 charge to mass ratio of the electron revised 92012, abg theory elementary particle physics has as its goal to know the properties of the many atomic and subatomic particles mesons, quarks, lambda particles, etc and to understand their place in nature.
A particle of mass m and charge e moving in a magnetic induction field b will. This expression can be simplified to give the charge to mass ratio as q m v rb 6 in the case of the electron, q e and m mass of the electron, me. The importance of the masstocharge ratio, according. We will then determine the electrons charge to mass ratio em experimentally and compare it to theoretical calculations using equation 8. Given that it is also possible to perform a measurement of e alone the millikan oil drop experiment, it is possible to obtain the value of the mass of the electron, a very. The magnetic field generated by a single loop charged particle in constant magnetic field. Wesley odom, leif peterson, joshua williams, elena gregg phd the department of engineering oral roberts university introduction theory experimental setup results conclusion the charge tomass ratio of an electron was measured using a method similar to. In this experiment you will use the relative positions of the emission lines of hydrogen and deuterium to the protonelectron mass ratio. They are same in charge and have the same physical properti. Electron chargetomass ratio name partners prelab you are required to finish this section before coming to lab. The electron charge to mass ratio was an experiment that was used to calculate the ratio of the electrons charge to its mass. Charge to mass ratio of an electron new york university.
Charge to mass ratio of the electron ryerson university. References reese, university physics, brookscole, 2000. Lab 5 electron chargetomass ratio l53 if one uses two coaxial coils of radius r that are a distance d apart, as shown in figure 5. The specific charge of the electron is determined from the.
This experiment was one of the first experiments to attempt to. Describe or make a rough sketch of the path of an electron traveling into a region with a constant bfield. J j thomsons experiment to determine the charge to mass ratio of an electron. Chargetomass ratio for the electron introduction this is a variation of the original experiment carried out by j. The first is the experiment of joseph john thomson, who first demonstrated that atoms are actually composed of aggregates of charged particles. Experiment q1 electron chargetomass ratio abstract the ratio em for electrons is determined by measuring the radius of curvature of the path followed by electrons of known velocity as they move in a known magnetic field. Chargetomass ratio for the electron u of t physics. The magnetic force on an electron is given by f ev b. His experimental apparatus is not very di erent from the one which you will use in this lab, and he was later awarded the nobel prize for his discovery. Physua 72 intro to exp physics ii charge to mass ratio of electron from left to right in fig. We will then determine the electron s charge to mass ratio em experimentally and compare it to theoretical calculations using equation 8. Thomsons experiment and the charge tomass ratio of the electron. Charge to mass ratio of electron new york university.
Thus in the nonrelativistic approximation, ev 1 2 mv2 3 combining eqs. Simulation of thomsons experiment to find charge to mass. Given that it is also possible to perform a measurement of e alone the millikan oil drop experiment, it is possible to obtain the. Electron chargetomass ratio university of virginia. Chapter 1 measurement of chargetomass em ratio for the electron experiment objectives. Charge to mass ratio of the electron vanderbilt university. Millikan 18681953 was able to measure the charge of the electron 1.
Students will observe the interaction between a magnetic field and an electron beam, and measure the charge to mass ratio of the electron. This experiment investigates the path of an electron in a magnetic field. Simulation of jj thomsons experiment to find the charge to mass ratio of an electron. In this experiment, electrons are \boiled o of a hot lament. Chargetomass ratio of the electron october 30, 2015 name. It is known that a current running through a solenoid creates a. He is also credited with the discovery of the electron itself. A beam of electrons was used that was subjected to a magnetic field that caused it to shift direction. Experiment 6 the chargetomass ratio of the electron. Charge to mass ratio of the electron julia velkovska september 2006 1. Charge to mass ratio of electron was found out using the jj thomson experiment. By measuring the deflection that a magnetic field produces on a beam of electrons having a known energy, you will deduce a value for the charge to mass ratio of electrons. From their response to electric and magnetic fields the ratio of charge to mass for the electron can be determined. The setup consists of an evacuated except for a low pressure of he gas cathode ray tube which produces a beam of electrons of variable energy.
Are there experiments where the charge to mass ratio for protons have been determined in the same way as in thompsons experiments where he determined the charge to mass ratio of electron but with protons instead of electrons. Notice that there are two sheets tabs for this file at bottom. In this experiment, you will perform a modification of thomsons original work. The charge to mass ratio em for the electron introduction in 1897 j. Introduction in this lab you will repeat a classic experiment which was first performed by j. Charge to mass ratio of an electron 2 theory let the mass, charge, radius, velocity, and acceleration of an electron be given by m, e, r, v, and v2rrespectively. Thomson had found a charged particle that had a specific. Electron charge and mass quantity symbol value units mass me 9. In this experiment you will be measuring the charge to mass ratio, em, of the electron.
To experimentally determine the electron chargetomass ratio overview in this experiment, you will measure em, the ratio of the electrons charge e to its mass m. Thomson first determined the specific charge charge to mass ratio em of the electron in 1887. Why is the charge of the mass ratio of an electron the. The charge to mass ratio of the electron 1 introduction in this exercise we will measure the charge to mass ratio of the electron by accelerating an electron beam through a known potential and measuring the radius of curvature of the beam in a known magnetic. So people mistook the positive particle produced in the experiments to be protons exclusively. Thomsons 1897 experiment in which he discovered the electron. The he apparatus consists of an electron gun, a helium filled vacuum tube. Thus, the objective of this experiment is to produce electrons of known velocity v moving in a known magnetic field, b, and to measure the radius, r, of their circular motion. Initially when experiments were conducted to find out the ratio,neutrons were yet to be discovered.
Charge to mass ratio of the electron introduction the electron was rst discovered by sir j. Abstract the classen em experiment performed was intended to demonstrate how the charge to mass ratio of an electron can be determined by allowing a current run through an apparatus known as the helmholtz coil. In measuring the charge to mass ratio eme in this experiment, the apparatus is arranged. Thomsons experiment and the chargetomass ratio of the electron. The first part of the experiment required varying circular helium electron paths with a constant accelerating voltage of 280 v. Experiment 6 the chargetomass ratio of the electron ucla. Now your problem is to find the mass difference between these two nucleus. The purpose of this lab is to determine the chargetomass ratio em of an electron by measuring the radius r of. Principle electrons are accelerated in an electric field and enter a magnetic field at right angles to the direction of motion. In this experiment you will measure em, the ratio of charge e to mass m of the electron. As vis perpendicular to b by experimental design, in terms of. Joseph john thomson performed an experiment, in which he successfully. This is a variation of the original experiment carried out by j.
Lab 5 electron chargetomass ratio university of virginia. The charge to mass ratio of electron is em is the ratio between the charge of the electron by the mass of the electron which is 1. Ratio of charge to mass em for the electron in this experiment we observe the motion of free electrons in a vacuum tube. He conducted a series of revolutionary experiments with cathode ray tubes. The value of the ratio of the absolute value of the charge to mass em is computed from the relationships between the measured accelerating potential difference, v, the magnetic field, b, and the radius of the circular path which the electron beam describes, r. Thompson discovered the first elementary particle, the electron, by measuring the ratio of its charge to mass in a manner similar to the experiment that we will. Electron charge to mass ratio matthew norton, chris bush. Thomson rst measured the chargetomass ratio of the fundamental particle of charge in a cathode ray tube in 1897. The experiment showed cathode rays to be a stream of particles, each with the same charge to mass ratio, which he measured.
The value of the ratio of charge to mass em is computed from the relationships between the measured accelerating potential difference, the magnetic flux density, and the diameter of the circular path which the electron beam describes. It appears in the scientific fields of electron microscopy, cathode ray tubes, accelerator physics, nuclear physics, auger electron spectroscopy, cosmology and mass spectrometry. Introduction and theory around the turn o f the century, two dramatic experiments established the existence of the electron, a charged particle that is very much smaller than an atom in size and in mass. Experiment q1 electron chargetomass ratio abstract. If a uniform magnetic field b is perpendicular to the initial direction of motion of an electron beam, the electrons will be deflected by a force that is always. Fortunately, the ratio of these two fundamental constants can be determined easily and precisely from the radius of. In this experiment, the electron originates from the cathode with a negligible initial velocity. Youre guided through the simulation and the calculations. Simulation of thomsons experiment to measure the charge to mass ratio of an electron, with calculations. Measurement of chargetomass em ratio for the electron. Charge to mass ratio of electron ohio wesleyan university.
Measurement of chargetomass em ratio for the electron experiment objectives. Fundamental physics experiments charge to mass ratio of. Determination of the specific charge of the electron em from the path of an electron beam. Use this physical model to design an experiment to measure the charge to mass ratio of an electron as well as the. Motivation and history of the first em measurement consequences thomsons experiment the physics behind the experiment.
Quantities which are directly measurable in this lab are the accelerating voltage v, radius of the electrons path r, and the magnetic eld b. Name the 2 forces that are equated in order to derive the charge to mass ratio relationship. Chapter 1 measurement of chargetomass em ratio for the. Combine your results from steps 6 and 9 to write a formula which relates the radius of the electrons path rto. The masstocharge ratio mq is a physical quantity that is most widely used in the electrodynamics of charged particles, e.
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