# Summary of the E/M Ratio for Electron

• The main goal for the e/m ratio lab was to experimentally find the ratio of electric charge to mass for an electron. You do this by producing free electrons using an electron gun and moving them through a magnetic field in a circular orbit and measuring the radii of the electrons. The value I obtained the value $\frac{e}{m}=2.3(\pm .23)\times 10^{11}\frac{coul}{kg}$ SJK 17:57, 15 November 2009 (EST)
17:57, 15 November 2009 (EST)
It would be better to write this as 2.30 ± 0.23 or 2.30(23)
through the experiment this includes a SEM which i obtained using the computer program Excel and I talk about in my lab notebook for this lab. My error in this lab was 30.68% as compared to the value from Dr. Golds lab manual SJK 17:45, 15 November 2009 (EST)
17:45, 15 November 2009 (EST)
You should write the accepted value here, though it's good you cite your source. More than that, you should compare the discrepancy from the accepted value with your uncertainty range. That is, you are many times farther away from the accepted value than the size of your SEM. Thus there must be substantial systematic error.
. I think is not too bad for this lab considering that some of the main readings were taken by measuring a radii by the naked eye and then expanding this do give a value for the e/m. This could have been done with more precision if there was a way to measure the radii with some sort of electronic medium that would give a more precise reading but alas this was not so in this lab.
• The underlying physics of this lab are that of electricity and magnetism. Specifically those associated by a Helmholtz Coil and the magnetic field it generates which is used to create the circular orbit the electron will travel along. Also how fast an electron is accelerated or the Lorenz Force applied to the electron, in an electric field which is obtained by the used of an electron gun in that it creates an electron with a certain amount of energy witch is associated with the voltage applied to the electron gun. Using all of this you can find out how the electron will respond to the magnetic field and using this data you can find the ratio of the electrons charge compared to its mass.
• All of the data that I obtained was from the use of voltmeters witch were used to find the voltage that was applied to the electron gun and thus the Lorenz force on the electron. The voltmeter was also used to find the current that was applied to the Helmholtz Coils which can be used to find the magnetic field in witch the accelerated electron travels. The last measurement we obtain is that of the radii that the electron will travel from when the electron leaves the electron gun to when the electron completes it travels and comes back around to the electron gun a roughly circular orbit. These readings will have the most error due to the fact that you have to line up the electron orbit by just seeing the circular orbit of the electron beam and lining it up to a ruler attached to the back to the e/m apparatus which just leaves the most error to be generated in terms of it being dependent on where you think that the radii is in relation to the ruler.