• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6
  7. 7
  8. 8
  9. 9
  10. 10
  11. 11
  12. 12
  13. 13
  14. 14

Charge To Mass Ratio For An Electron

Extracts from this document...


Physics Formal Lab Charge To Mass Ratio For An Electron Professor: Dr.Kilner Ta: Mr.Laderman Done by: Amir Mofidi 010238350 Section 004 Abstract How electrons behave in the presence of a magnetic field was the purpose of this lab. In particular, how there is a force acting on the electron in a magnetic field related to its velocity; or in other words the force acting on the electrons will cause them to move in a circular path. Measuring the charge to mass ratio of an electron using an apparatus which fires electrons into a uniform magnetic field produced by Helmholtz coils; the particles follow a circular path. The anode voltage was set at 200v; the radius of the curvature of the electrons was changed by adjusting the Helmholtz coils current. Its radius ranges from 11cm to 6 cm; the strength of the magnetic field and the speed of the moving particles, one can figure out the charge to mass ratio. The value found for the ratio of electrons to mass to in this experiment would be 1.89�1011 coulombs/kg. Comparing this experimental value to the theoretical value which is 1.76�1011 coulombs/kg makes a 7.38% experimental error. ...read more.


To observe the circular motion of an electron beam in a nearly-uniform magnetic field and deduce the charge-to-mass ratio of the electron from measurements of the orbital radius. Based on theoretical calculations and experimental evidence, both the charge and the mass of an electron are constants, as is the ratio of the two. The magnetic field will induce a force on the electron which is perpendicular to both the direction and the magnetic field, and will force the electron beam to curve. The radius of curvature can be used to calculate the charge-to-mass ratio, since the curvature is directly related to both the mass of the electron and its charge. Method In this experiment the equipments were set up as in figure3. Figure 3 At the base of the e/m apparatus are inputs for the heater filament voltage (the cathode from which the electrons will be emitted), the anode voltage (the voltage through which the electrons will be accelerated), and the Helmholtz coil current. 6 volts from the output of the power supply was applied to the heater inputs located on the base of the e/m apparatus. The discharge tube power supply was turned on and the cathode glow red hot. ...read more.


It is fair to say that this simple experiment sparked a line of research which drastically changed our way of thinking about the universe. Aside from the thrill of repeating an important and historic experiment, this lab is an ideal forum for exploring the motion of charged particles in electric and magnetic fields. At the end of the day, it is to be known how to calculate the electromagnetic force on a particle in any field configuration. Conclusion In this experiment you will observe the behavior of electrons in a magnetic field and determine a value for the electron charge-to-mass ratio e/m. Although it ended up with a 7.38% error it is still an acceptable value for this experiment. The final observed value for e/m turned out to be 1.89�1011 coulombs/kg. Considering the inherent difficulties associated with the experiment, the results are astonishingly accurate. One difficulty was accurately measuring the radius of the beam on the ruler due to that the room was not dark enough and it made it hard to see the exact radius of the beam. Second the Helmholtz coils where not orient parallel to the direction of the earth's magnetic filed (about 15? east of geographic north); so the effect of the earth's magnetic filed was not minimized and it had its effects in this experiment. At the end it was very interesting lab with very good results. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Fields & Forces section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Fields & Forces essays

  1. Peer reviewed

    Investigating the forces acting on a trolley on a ramp

    5 star(s)

    in this experiment differ from the widely accepted value of g; 9.81ms-2. Because we already know that friction has a smaller impact on the results at higher values of O, this alone could explain the error and trends shown in the values for g.

  2. Investigation to determine the viscosity of glycerol.

    This prevents accurate determination of the point at which a body reaches terminal velocity. The importance of knowing the point at which a sphere reaches terminal velocity is because at this point the forces acting on the sphere are balanced.

  1. Investigating a factor affecting the voltage output of a transformer.

    coils, I will also aim to standardise each repetition of the procedure to obtain a fair test. To achieve this I shall use the same core, lengths of same wire for coils, voltmeters, connective wires, a.c. supply, etc. All conditions other than primary voltage should be kept constant to obtain a fair test.

  2. The experiment involves the determination, of the effective mass of a spring (ms) and ...

    Hence the order of the readings. Main Readings Mass/Kg x number of oscillation's Time for x oscillations ( in seconds) xT av/s T/s T2/s2 ?xT/s % unc in xT % unc in T2 ?T2/s2 0.100 0.200 0.250 0.300 0.400 0.450 0.500 0.600 50 40 35 30 25 30 25 25

  1. Modeling a basketball shoot in the lab

    How to model a basketball shot? The general idea of this experiment is to give a constant force on a ball at a certain angle, aiming to land on a sand pit as follow. Figure 3. The general experimental set up Apparatus - - Spring loaded plunger - A 'run way' - Lab Jack - Clamp

  2. Einstein's theory of relativity.

    Euclidian or "flat" geometry cannot describe curved space. Thus, Einstein used geometries called Riemannian geometries to describe the effects of gravitation. According to Newton's theory, a planet moves around the sun because of the gravitational force exerted by the sun. According to the theory of general relativity, the planet chooses the shortest possible path throughout the four-dimensional world, which is deformed by the presence of the sun.

  1. What Affects the Strength of Magnetism Exerted By an Electromagnet?

    This could be because not all the lines of flux result in contacting the metal. Thus, some of the power is always lost. These stray lines of flux will head either towards the sources opposite pole, any obstructing or nearby pieces of metal, or the 'Earth's Molten Metallic' core.

  2. Aurora- Light of Mystery.

    everyday environment because most of the materials we encounter in everyday life are electrically neutral. In fact this field has been protecting the earth's atmosphere by stopping the solar wind in a magnetic shock wave. Without this magnetic field, the atmosphere will be exposed to the high-energy solar wind and the solar particles will strip the air of the earth.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work