Electron Physics Lab
Introduction
The purpose of this lab is to examine the motion of an electron, when it encounters a constant magnetic and electric field. We will also observe when the electric field and magnetic field will cancel each other out. This will lead to the electron having no net force acting upon it. By adjusting the values for the magnetic and electric fields, we will be able to check the different paths the electron follows. From this data we will be able to calculate the charge-to-mass ratio. Then, using the accepted value, we can calculate the percentage error.
This lab requires the use of two important pieces of equipment: the Helmholtz Coils and the deflection tube. The Helmholtz coils are used to generate the constant magnetic field. …show more content…
The power supply sends a current through the coils. This current generates a constant magnetic field which acts on the electron. The deflection tube is the device that emits the ray of electrons. The electrons get emitted because a filament wire becomes heated and releases the electrons. The electron beam becomes visible on the mica sheet. There are also two deflection plates on the top and bottom which create a potential difference between them. Because of this potential difference there is an electric field that is produced and acts on the electron. 6.3.1 Magnetic Deflection
Objective: To determine the charge-to-mass ratio for an electron by using a magnetic field.
We will run a current through the Helmholtz coils to create a magnetic field. We will alter the values for the accelerating voltage (Va) and the current through the Helmholtz coils (Ib) and measure the radius of the trajectory. With our calculated values for e/m we will compare it to the accepted values.
Data and …show more content…
Explanations:
Positive Deflection
Va(V) x (m) y (m) Ib (A) B (T) R (m) e/m (C/kg)
2500 0.10 0.02 0.152 6.43 x 10^-4 0.26 1.79 x 10^11
3000 0.07 0.01 0.167 7.06 x 10^-4 0.25 1.93 x 10^11
3500 0.08 0.0.12 0.136 5.80 x 10^-4 0.325 1.97 x10^11
Negative Deflection
Va (V) x (m) y (m) Ib (A) B (T) R (m) e/m (C/kg)
2500 0.08 -0.01 0.152 6.43 x 10^-4 0.325 1.14x10^11
3000 0.09 -0.01 0.133 5.63 x 10^-4 0.41 1.13x10^11
3500 0.08 -0.01 0.169 7.15 x 10^-4 0.325 1.97x10^11
Mean e/m (C/kg) Standard Deviation Standard Deviation of the Mean
1.54x10^11 +/- 1.618x10^10 3.963x10^10 1.618x10^10
Analysis:
To obtain the e/m ratio we varied the accelerating voltage. When we varied this voltage we changed the velocity at which the electrons traveled. We also adjusted the current in the coils, so that the beam traveled across a
We used the equation 6.4, B(T)=k*Ib, to find the magnitude of the magnetic field (in teslas) where k is a constant equal to 4.23*10^-3. To determine the radius of the trajectory, we used equation 6.6 in the manual (R= (x2 + y2)/(2y)). Finally, the charge-to-mass ratio was calculated using the equation: e/m = (2Va) / (B2*R2). The e/m equation was derived from equations 6.1, 6.2 and 6.3. The mean and standard deviations were calculated using the equations from the appendix in the lab manual.
Both positive and negative deflection values were observed to reduce our uncertainty and error in the data.
The more data points we use for these types of calculations the more accurate our data will turn out to be.
Based on our error analysis our final experimental value for the charge-to-mass ratio is: e/m = 1.54x10^11 +/- 1.618x10^10 C/kg
This seems to be fairly close to the accepted value of 1.7589*10^11 C/kg. However, the accepted value does not fit into our range. The discrepancy could have come from misreading of the x and y values from the mica sheet. It was sometimes hard to get exact values for the x and y. This could have been the reason for the difference between the accepted and observed values.
6.3.2 Electrostatic Deflection
Objective: The purpose of the lab was to create a potential difference between the deflection plates of the plates and measure various x and y values at fixed values of Va and Vd. With this data we will make a graph of y vs. x2 and then use this graph to calculate the value of the Electric field and find why and how the beam is deflected differently in compared to the magnetic field.
Data:
Va = 2470 Volts
Vd= 3000 Volts d = 0.051 m
The purpose of this lab is to examine the motion of an electron, when it encounters a constant magnetic and electric field. We will also observe when the electric field and magnetic field will cancel each other out. This will lead to the electron having no net force acting upon it. By adjusting the values for the magnetic and electric fields, we will be able to check the different paths the electron follows. From this data we will be able to calculate the charge-to-mass ratio. Then, using the accepted value, we can calculate the percentage error.
This lab requires the use of two important pieces of equipment: the Helmholtz Coils and the deflection tube. The Helmholtz coils are used to generate the constant magnetic field. …show more content…
The power supply sends a current through the coils. This current generates a constant magnetic field which acts on the electron. The deflection tube is the device that emits the ray of electrons. The electrons get emitted because a filament wire becomes heated and releases the electrons. The electron beam becomes visible on the mica sheet. There are also two deflection plates on the top and bottom which create a potential difference between them. Because of this potential difference there is an electric field that is produced and acts on the electron. 6.3.1 Magnetic Deflection
Objective: To determine the charge-to-mass ratio for an electron by using a magnetic field.
We will run a current through the Helmholtz coils to create a magnetic field. We will alter the values for the accelerating voltage (Va) and the current through the Helmholtz coils (Ib) and measure the radius of the trajectory. With our calculated values for e/m we will compare it to the accepted values.
Data and …show more content…
Explanations:
Positive Deflection
Va(V) x (m) y (m) Ib (A) B (T) R (m) e/m (C/kg)
2500 0.10 0.02 0.152 6.43 x 10^-4 0.26 1.79 x 10^11
3000 0.07 0.01 0.167 7.06 x 10^-4 0.25 1.93 x 10^11
3500 0.08 0.0.12 0.136 5.80 x 10^-4 0.325 1.97 x10^11
Negative Deflection
Va (V) x (m) y (m) Ib (A) B (T) R (m) e/m (C/kg)
2500 0.08 -0.01 0.152 6.43 x 10^-4 0.325 1.14x10^11
3000 0.09 -0.01 0.133 5.63 x 10^-4 0.41 1.13x10^11
3500 0.08 -0.01 0.169 7.15 x 10^-4 0.325 1.97x10^11
Mean e/m (C/kg) Standard Deviation Standard Deviation of the Mean
1.54x10^11 +/- 1.618x10^10 3.963x10^10 1.618x10^10
Analysis:
To obtain the e/m ratio we varied the accelerating voltage. When we varied this voltage we changed the velocity at which the electrons traveled. We also adjusted the current in the coils, so that the beam traveled across a
We used the equation 6.4, B(T)=k*Ib, to find the magnitude of the magnetic field (in teslas) where k is a constant equal to 4.23*10^-3. To determine the radius of the trajectory, we used equation 6.6 in the manual (R= (x2 + y2)/(2y)). Finally, the charge-to-mass ratio was calculated using the equation: e/m = (2Va) / (B2*R2). The e/m equation was derived from equations 6.1, 6.2 and 6.3. The mean and standard deviations were calculated using the equations from the appendix in the lab manual.
Both positive and negative deflection values were observed to reduce our uncertainty and error in the data.
The more data points we use for these types of calculations the more accurate our data will turn out to be.
Based on our error analysis our final experimental value for the charge-to-mass ratio is: e/m = 1.54x10^11 +/- 1.618x10^10 C/kg
This seems to be fairly close to the accepted value of 1.7589*10^11 C/kg. However, the accepted value does not fit into our range. The discrepancy could have come from misreading of the x and y values from the mica sheet. It was sometimes hard to get exact values for the x and y. This could have been the reason for the difference between the accepted and observed values.
6.3.2 Electrostatic Deflection
Objective: The purpose of the lab was to create a potential difference between the deflection plates of the plates and measure various x and y values at fixed values of Va and Vd. With this data we will make a graph of y vs. x2 and then use this graph to calculate the value of the Electric field and find why and how the beam is deflected differently in compared to the magnetic field.
Data:
Va = 2470 Volts
Vd= 3000 Volts d = 0.051 m