WorksheetsThermionic Emission
Total questions: 15
Worksheet time: 11mins
one of the properties of cathode rays is
positive charge
does not move in a straight line
can be deflected by electrical field
cannot be deflected by magnetic field
If an electric field is put across the beam with the positive plate on top and the negative plate below.
The beam will bend
Up
down
left
right
in a circle
I use thermionic emission to emit a stream of electrons and display them on a screen.
Cathode-Ray Oscilloscope
Raster-Scan Display
Random-Scan Display
Process of emission of electrons from hot metal surfaces is called
photoelectric effect
thermionic emission
static emission
emission current
Particles emitted from a hot cathode surface are:
negative ions
photon
protons
electrons
Cathode rays carry
negative charge
positvie charge
neutral particles
electrons and protons
Cathode rays can be deflected by
electric fields only
magnetic fields only
quantum fields
magnetic and electric fields
Why is a vacuum needed in the tube?
It makes the process more efficient.
It impedes or slows down the electrons.
It allows the electrons to flow unimpeded.
It allows the electrons to be made into a beam.
How are the electrons made into a beam?
Using a high voltage across the tube.
Use of an anode to spread the electrons.
Use of positive anode to focus the electrons.
Use of a fluorescent coating at the end of the tube.
How is the electron beam detected?
Use of a fluorescent screen.
By deflecting the beam of electrons with a magnetic field.
By deflecting the beam of electrons with an electric field.
Using an electron microscope.
what happens when cathode rays strike the fluorescent screen
electron bounces back
nothing happens
emit light
produce current
how to increase the rate of thermionic emission
immerse metal in an electrolyte
increase the surrounding pressure
decrease the temperature of metal to stabilize electron
increase the surface area of the metal
what happen to the electron when when it is emitted from the cathode or metal?
move around the cathode
attract toward the anode
attract toward the cathode
goes back to cathode to form equilibrium state
what can be used to control the direction of the cathode ray
electrical field
gravitational field
heat energy
quantum field
what is the purpose of connecting anode with high voltage d.c power supply
to deflect or change the direction of the electron
to accelerate the electron
to deceleration the electron
to increase the rate of thermionic emission
