Turning Points: Electrons Flashcards
What creates when a high potential difference is supplied between cathode and anode?
An Electric field
What happens to the gas atoms in a discharge tube?
The electric field pulls out gas atom’s electrons and make them positive ions. This helps the ions to accelerate towards the cathode.
What kind of pressure is needed for the gas atoms to move around?
Low Pressure
What happens when the positive ions travel towards the cathode?
The ions have enough speed to collide with the cathode and causes the large number of electrons to be emitted from the cathode’s metal surface.
What happens to the electrons after it is emitted from the cathode’s surface?
The get accelerated towards the anode and collide with gas atoms. This causes the them to be excited. The de-excitation causes the emission of visible and ultraviolet photons.
What is the term conducting?
The movement of electrons toward the anode and the positive ion towards the cathode.
What happens if the pressure is reduced further
Greater speed of electrons after ejected from cathode’s surface.
What is the process of thermionic emission?
The current flowing through causes the filament to heat up. Free electrons would have enough energy to leave the surface. The energy supplied for the electron must be greater than or equal to the work function.
What happens when we increase the temperature in thermionic emission?
temperature of cathode increases, more electrons are ejected, so density of electrons increases
What is the equation for speed of an electron from an electron gun?
1/2 mv2 = eV
In Millikan’s experiment, when applying voltage between P1 and P2, what created and the on the oil droplets?
a uniform electric field and and an electric force on oil droplet
In Millikan’s experiment, what is the initial equation relating weight and distance between plate?
mg = QV/d
In Millikan’s experiment, what was the first step to identify the radius of oil droplet?
He observed the motion of droplet with no electric field so only weight and air resistance is experienced. Hence reaching terminal velocity
In Millikan’s experiment, what does the drag determine by?
object’s size, shape and speed
In Millikan’s experiment, what was the equation to show weight and drag?
mg = 6 pi nrv
