2. Calculation of the number of quanta for heating:
Given:
Frequency (take the upper threshold of microwave radiation):
f = 300 GHz
Solving:
Change in body heat when exposed to quanta:
(7)
Hence, the number of quanta required to heat the body to a certain temperature:
=
(8)
Quantum energy (1):
Calculate the number of quanta needed to heat the body in everyday life:
Let's calculate the number of quanta needed to heat the body in production:
We
conclude that the number of quanta needed to heat the body in
production is
/
= 7 times greater than the number of quanta needed for heating in
everyday life.
Answer:
Body
temperature change in everyday life:
;
Body
temperature change in production:
;
The number
of quanta for heating in everyday life:
;
The number
of quanta for heating in production:
;
0.75 балл
Task №3
3. Compare numerically 2 typical devices: vacuum and semiconductor according to the following parameters:
3.1 The maximum velocity of charged particles.
3.2 The length of the interaction region for the angle of flight-radian.
3.3 Volumetric charge density
3.4 Calculate the microperviance, the «plasma» frequency for the vacuum device.
3.5 For semiconductor: Debye length, plasma frequency.
Compare the values in clauses 4.4. and 4.5. Explain the difference in physical processes in both variants.
Parameters of the vacuum device: current 120 mA, accelerating voltage 5,2 kV, flow diameter 14 mm.
Semiconductor: doping level 6 1016 cm-3, voltage 20 V, current channel thickness 1 microns.
The operating frequency of the devices is 13 GHz.
The operating temperature is 306 K.
Given:
Parameters of the vacuum device:
IV = 120 mA
UV = 5,2 kV
d = 14 mm = 0,014 m
Parameters of a semiconductor device:
n = 6 1016 cm-3 = 6 1022 m-3
US = 20 V
h
= 1
= 10-6
m
Operating frequency of both devices:
f = 13 GHz
Operating temperature of both devices:
T = 306 K
Solving:
1. Numerical comparison of the maximum velocities of charged particles:
1.1 Vacuum device:
According to the formula [11]:
VVmax
=
(9)
where q - electron charge; m - electron mass; UV – accelerating voltage.
We get the following value:
VVmax
=
=
=
4,276
107
m/s
1.2 Semiconductor device:
Field strength:
E
=
=
=
200 kV/cm
So, the maximum speed corresponds to the saturation current [12]:
VSmax = Vsat= 105 m/s
Thus, the maximum velocity of charged particles in a vacuum device is 4,276 107/105 = 428 times greater than in a semiconductor device.
2. Numerical comparison of the length of the interaction region for the span angle of π - radians:
2.1 Vacuum device:
The formula of the span angle [13]:
=
=
(10)
where f – frequency; lV - the length of the interaction area; vV - flight speed.
Hence, the length of the interaction area:
lВ
=
=
=
=
=
=
0,00164 m
2.2 Semiconductor device:
lS
=
=
=
=
=
=
3,846
10-6
m
That is, the length of the interaction region of the vacuum device is 0,00164/3,846 10-6 = 426 times longer.