Electrons

5.1  Electrons
 
  Thermionic emmision  
  The release of electrons from the heated metal surface.  
     
 
 

The factor that influences thermionic emission:

  1. The temperature of the cathode
    • As the temperature of the cathode increases, the rate of thermionic emission increases.
  2. The surface area of the cathode
    • As the surface area of ​​the cathode increases, the rate of thermionic emission increases.
  3. The potential difference between anode and cathode
    • As the potential difference between the anode and the cathode increases, the electron velocity increases, causing the electron beam to accelerate.
  4. The type of cathode
    • Made of tungsten.
  5. Cathode plating
    • Barium oxide, strontium oxide

      (lower the temperature for the beam)

 
 

The characteristics of cathode rays:

  1. Move-in a straight line at high velocity.
  2. Has momentum and kinetic energy.
  3. Kinetic energy \(\rightarrow\) light energy when an electron hits a fluorescent screen.

  4. Produces X-rays when exposed to heavy metals.

  5. Charged –ve.

  6. Can be deflected by magnetic field (Fleming left hand).