EE 403/503
October 16, 2003
Midterm
Open Book Exam
- Each question has 10 points.
- Total time for the exam is 60 minutes.
Some of the physical constants are:
h = 6.63 x 10-34 [Js]
k = 1.38 x 10-23 [J/K]
c = 2.998 x 10+8 [m/s]
me= 9.1 x 10+31 [Kg]
mH = 1.66 x 10-27 [Kg]
NAvogadro= 6.02 x 10+23 [/gmole]
e = 1.6 x 10-19 [C]
1 atm = 101325 [N/m2] = 760 Torr
The table below contains the data for two different type of hydrogen discharges.
This table is required for answering the questions:
Discharge # Telectrons [K] Tatoms=Tions [K] Pressure [Torr] na [m-3]
1
10000
10000
760
5x10+23
-2
2
100000
500
10
7x10+17
Circle the best Answer!
1- What is the number density of the electrons of the plasma in tube # 2?
a) 1.2 x 10+23
b) 2.7 x 10+21
c) 9.2 x 10+19
d) 9.6 x 10+17
e) None of the above
2- How much is the average kinetic energy of electrons in eV in tube # 1?
a) 1.2 x 10-18
b) 1.29
c) 1.6
d) 1.2 x 10-17
e) None of the above
3- What type of discharges do we have in the above table? Show them in the
following graph.
105
Thermonuclear
Plasmas
Average Electron Energy, [eV]
104
Electron
Beam
103
Solar
Corona
102
101
Interstellar
Gas
Gaseous
Nebulae
Glow
Discharge
Arc
Discharge
100
Ionosphere
MHD
Generator
Solid
10-1
100 102 104 106 108 1010 1012 1014 1016 1018 1020 1022 1024
Electron Number density, [cm-3]
4- In collision between two electrons, assuming one of them at rest:
a) collision is elastic and maximum energy exchange is 50% of the total.
b) collision is inelastic and maximum energy exchange is 50% of the total.
c) collision is elastic and maximum energy exchange is 100% of the total.
d) collision is inelastic and maximum energy exchange is 100% of the total.
e) none of the above
5- Electromagnetic waves resonate with the discharge when its frequency is the
same as the plasma frequency. At what wavelength radiation will resonate with
the discharge # 2 ?
a) 1.5 x 10+17
b) 3.1 x 10+12
c) 8.8 x 10+9
d) 6.3 x 10+7
e) None of the above
6- What equation is most useful in determining population density of excited states
a) Maxwellian distribution
b) Maxwell’s equations
c) Planck’s function
d) Boltzmann distribution
e) Saha equation


and B are parallel. Initial velocity of an electron is perpendicular to E and
7- E
B. Draw the electron path.
Velectron
electron
B
E
8- When a particle inserted into the discharge # 2, a plasma sheath is formed around
its surface. How many ions enter the plasma sheath from the plasma per second?
a) 4.26 x 10+26
b) 3.21 x 10+17
c) 7.82 x 10+20
d) 1.2 x 10+15
e) None of the above
9- How does a metastable atom most likely affect the discharge?
a) increases the impact ionization
b) Enhances the space charge in front of the cathode
c) Enhances the secondary emission
d) Reduces the discharge current
e) None of the above
10- The workfunction can be best explain by the
a) Tunnel effect
b) Fowler and Northeim effect
c) RichardsonEquation
d) Schottky mirror image
e) None of the above