Physics Electron Gun Magnetic Field 
October 30, 2014
Jordan Hollenbeck
Juhn Borruel
Electron Gun - Effects of a Magnetic Field
Purpose: The objective of this experiment is to study the motion of an electron in a magnetic field and to establish (show/verify) a relationship between the magnetic strength and the distance the electrons are deflected.
Theory and Procedure: The electron gun is an instrument that consists of an electron source
(which emits electrons and focus the stream into a beam), a magnetic coil (which uses a voltage to create a magnetic field that deflects the beam away from the center line), and a phosphorus screen (which illuminates when the beam comes in contact with it).
The electron source contains an electrically heated filament (cathode) and an anode to create an electron source and control the intensity (brightness) of an electron beam. Between the two, is the accelerating voltage (?Va). This voltage determines the velocity of the electron beam.
The electrons then pass through the magnetic coil (with length lc). The magnetic coil generate a magnetic field (B) when a voltage (?Vd) is supplied to both ends of the coil, creating a current (I). A force (Fy) appears perpendicular to the electron’s velocity
(vx) and the direction of the magnetic field, given by the following formula;
Fy = evxBsin(theta) where e is the charge of the electron and theta is the angle between vx and B
(sin(90)=1). Therefore, the equation simplifies to the following;
Fy = evxB
Because Fy is directly proportional to B, it ’pushes’ the electron further away from the center line as B increases. The electron’s horizontal velocity (vx) remains the same, but as it deflects away from the centerline, it’s gains a vertical component to its velocity
(vy) . When it hits the phosphorus screen, the electron will be a distance (?y) from the x-axis (centerline). In order to find ?y, we must consider the following equations; ay = Fy /m (ay is the acceleration of the electron and m is its mass) vy = (the initial vy which
Jordan Hollenbeck
Juhn Borruel
Electron Gun - Effects of a Magnetic Field
Purpose: The objective of this experiment is to study the motion of an electron in a magnetic field and to establish (show/verify) a relationship between the magnetic strength and the distance the electrons are deflected.
Theory and Procedure: The electron gun is an instrument that consists of an electron source
(which emits electrons and focus the stream into a beam), a magnetic coil (which uses a voltage to create a magnetic field that deflects the beam away from the center line), and a phosphorus screen (which illuminates when the beam comes in contact with it).
The electron source contains an electrically heated filament (cathode) and an anode to create an electron source and control the intensity (brightness) of an electron beam. Between the two, is the accelerating voltage (?Va). This voltage determines the velocity of the electron beam.
The electrons then pass through the magnetic coil (with length lc). The magnetic coil generate a magnetic field (B) when a voltage (?Vd) is supplied to both ends of the coil, creating a current (I). A force (Fy) appears perpendicular to the electron’s velocity
(vx) and the direction of the magnetic field, given by the following formula;
Fy = evxBsin(theta) where e is the charge of the electron and theta is the angle between vx and B
(sin(90)=1). Therefore, the equation simplifies to the following;
Fy = evxB
Because Fy is directly proportional to B, it ’pushes’ the electron further away from the center line as B increases. The electron’s horizontal velocity (vx) remains the same, but as it deflects away from the centerline, it’s gains a vertical component to its velocity
(vy) . When it hits the phosphorus screen, the electron will be a distance (?y) from the x-axis (centerline). In order to find ?y, we must consider the following equations; ay = Fy /m (ay is the acceleration of the electron and m is its mass) vy = (the initial vy which