ELECTRIC FIELD-LESSON- 4

2. Electron beams
Q)What is thermionic emission?
When a cathode is heated electrons are emitted from its
surface. This is thermionic emission. When a high potential is
applied between the cathode and anode the emitted electrons
are attracted towards the anode.
As the electrons accelerate in the 1
field between the anode and
cathode, they lose potential energy 2
but gain K:E.
Gain in K:E = Loss in Electric P:E
1/2mv²=eV
m=mass of the electron,
v=velocity of the electron,
V=Potential between the plates,
e= charge of the electron.

4. Deflecting electron beams
An electron beam will follow a curved path when
subjected to a perpendicular elecric field.
This is because the electron is subjected to a vertical
force(F) due to the electric field.
F= eE=e V/d

5. Page 259.Example 4

6. Page.260 Example.5