Turning Points Flashcards
DEFINE: anode
Positive electrode
Describe a discharge tube
Evacuated glass tube with a cathode and anode filled with gas
What did JJ Thompson demonstrate about cathode Rays?
They have energy, momentum & mass. Are negatively charged and have bigger charge to mass ratio than a hydrogen ion
What is thermionic emission?
Process in which electrons gain enough thermal energy to break free from the surface of a metal.
Why is an electron gun made from a evacuated glass tube?
Because electrons are so small they are easily deflected or stopped by atoms, evacuating the tube allows the electrons to move freely
What causes the electrons to accelerate in a electron gun?
The electrons are accelerated from the cathode towards the anode because of the electric field caused by high potential difference (voltage)
Increasing the potential difference between the cathode and anode causes the electrons to…
Move faster because they have more kinetic energy
Why do the electrons passing through the gap at the anode move at a constant velocity?
There is no longer a force on them because there is no electric field beyond the anode
DEFINE: specific charge
Charge to mass ratio of an particle.
Describe a fine beam tube set up that can be used to measure e➗m, and how the path of the electrons can be traced through the tube.
A beam of electrons from a electron gun is passed through low pressure hydrogen gas at right angles to a uniform magnetic field. The field causes the beam to bend into a circle, the path can be seen because as the electrons collide with the gas molecules energy is transferred causing the electrons to excite and de excite releasing a photon of visible light.
Equation for radius of the circle of electrons in the fine beam tube?
R= mv➗bq
Significance of Thomsons findings of specific charge
It was the largest specific charge that has ever been measured, which meant the electron either had a greater charge or much smaller mass.
What is stokes law? (Oil drop experiment)
The viscous drag force works in the opposite direction to the particles velocity and is equal to f=6♊️nrv
How did the oil drops become charged?
fine mist of electrons charged by friction as they leave the Atomiser
DEFINE: cathode
Negative electrode
