The current in different media

Содержание и основные понятия

The nature of chargers depends on the environment: electrons in metal and vacuum, ions in electrolyte, electrons and ion in gas, electron and holes in a semiconductor.
GEF · 10 grade
PIF · Baseline
Interactive model
electrolysis
ionization
vacuum
Semiconductor
p-n-transition
01
The physical picture
What happens and what boundaries the model has.
Main message
The nature of chargers depends on the environment: electrons in metal and vacuum, ions in electrolyte, electrons and ion in gas, electron and holes in a semiconductor.
Electrolysis is accompanied by transport of the substance and chemical transformations on electrodes.
The gas discharge requires ionization and can become independent.
The conductivity of the semiconductor depends heavily on temperature, lighting, and contamination.
How to reason
First, name the system and the interaction, then select the values, and only then write down the law. The formula works within the model's assumptions.
02
Laws and values
Symbols should be read as a relationship of values, not as a recipe for substitution.
m
=
k
I
t
m=kIt
m
=
k
I
t
electrolysis law
I
=
∣
q
∣
n
S
v
d
I=|q|nSv_{\mathrm d}
I
=
∣
q
∣
n
S
v
d
​
current through host concentration
Review of the situation
The diode passes significant currents mainly in one direction due to the properties of the p–n-transition.
04
Links and application
In the real world
The diode passes significant currents mainly in one direction due to the properties of the p–n-transition.
Model verification
Compare the prediction with observation, evaluate the units, the order of magnitude and the influence of the factors not taken into account. Disparity does not always mean an error of law: often idealization is no longer sufficient.
C
What needs to be understood
Outcome 1
Explain the physical meaning of the topic "Took in different media" through the model, not just the formula.
Outcome 2
Clear and correctly use terms: electrolysis, ionization, vacuum.
Outcome 3
Indicate the conditions for the applicability of the law, verify units and limit cases.
T
Terms of the topic
The definition should indicate the physical meaning, not a substitute for a domestic synonym.
electrolysis
Chemical processes on electrodes through electrolyte.
ionization
The formation of charged particles from neutral atoms or molecules when the electrons are lost or joined.
vacuum
The space area with particle concentration is significantly lower than the normal gas.
Semiconductor
Material whose conductivity depends heavily on temperature, lighting, and contamination.
p-n-transition
The boundary of the semiconductor areas with a hole and electronic conductivity having a straightening characteristic.
F
Origin and conclusion of the formulas
The fundamental law cannot be "proven" by algebras: for each record, it is stated whether it is a definition, an experimental law, or a model effect.
m
=
k
I
t
m=kIt
m
=
k
I
t
empirical law
The law of electrolysis.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
m
∝
q
m\propto q
m
∝
q
Faraday's experience shows that the mass of electrode material is proportional to the past charge.
m
=
k
q
m=kq
m
=
k
q
The electrochemical equivalent k is measured for the substance and the reaction.
q
=
I
t
⇒
m
=
k
I
t
q=It\quad\Rightarrow\quad m=kIt
q
=
I
t
⇒
m
=
k
I
t
When the current is constant, the last charge is equal to It, which gives the working formula.
Conditions:
Stationary electrolysis with DC and almost 100% current output; k refers to a specific ion, valence and electrode reaction.
Monitoring:
The dimensions of both parts shall coincide; the result shall be checked for sign, order and limit case.
I
=
∣
q
∣
n
S
v
d
I=|q|nSv_{\mathrm d}
I
=
∣
q
∣
n
S
v
d
​
model effect
It's through the host concentration.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
Δ
V
=
S
v
d
Δ
t
\Delta V=Sv_{\mathrm d}\Delta t
Δ
V
=
S
v
d
​
Δ
t
During Δt, the section passes through the host of a layer of v_d Δt length and volume Sv_d___t.
Δ
N
=
n
Δ
V
=
n
S
v
d
Δ
t
\Delta N=n\Delta V=nSv_{\mathrm d}\Delta t
Δ
N
=
n
Δ
V
=
n
S
v
d
​
Δ
t
The number of carriers in this volume is equal to the concentration of n multiplied by the volume.
I
=
∣
q
∣
Δ
N
Δ
t
=
∣
q
∣
n
S
v
d
I=\frac{|q|\Delta N}{\Delta t}=|q|nSv_{\mathrm d}
I
=
Δ
t
∣
q
∣Δ
N
​
=
∣
q
∣
n
S
v
d
​
The complete transferred charge is divided by time; in the reference entry v means the average drift speed.
Conditions:
I is the current force module; .q. is the charge module of a single carrier; vd is the average drift speed module. The flow is homogeneous and stationary; current density is used for a directed recording, and for several types of current holders the current is added together.
Monitoring:
The dimensions of both parts shall coincide; the result shall be checked for sign, order and limit case.
!
Model boundaries and typical errors
Error: Forget model condition
The formula cannot be transferred to any situation simply because of the overlap of letters. The key condition of this topic is that electrolysis is accompanied by transport of the substance and chemical transformations on electrodes.
How to Check the Mind
The gas discharge requires ionization and can become independent. Then check the unit, vector direction and result behaviour at zero or very large parameter.
Σ
Conclusion on the topic
The current in different media
The nature of chargers depends on the environment: electrons in metal and vacuum, ions in electrolyte, electrons and ion in gas, electron and holes in a semiconductor.
Electrolysis is accompanied by transport of the substance and chemical transformations on electrodes.
The gas discharge requires ionization and can become independent.
Any numerical result shall be accompanied by a unit, a sign and an explanation of its physical meaning.
The content is consistent with the FRP on Physics of the OS/OSS 2025 and the subject matter of the current lines of the PNP: I. M. Peryškin and co-authors (7–9), G. J. Mäkishev and coauthors (10–11), and with the lines "Engineers of the Future" and V. A. Kasyanov. The original texts are not reproduced, the text of the textbooks is not reproduced.