Self-induction

Содержание и основные понятия

The current change in the circuit changes its own magnetic flow and creates an EDS that prevents it. Induction depends on geometry and the heart.
GEF · 11 grade
PIF · Baseline
Interactive model
self-induction
Inductiveness
transition process
RL chain
01
The physical picture
What happens and what boundaries the model has.
Main message
The current change in the circuit changes its own magnetic flow and creates an EDS that prevents it. Induction depends on geometry and the heart.
The current through the coil can't change with a leap in the perfect model.
When closed, inductiveness slows the current growth, keeping it open.
A sharp blackout can create high voltage.
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.
E
s
=
−
L
Δ
I
Δ
t
\mathcal{E}_s=-L\frac{\Delta I}{\Delta t}
E
s
​
=
−
L
Δ
t
Δ
I
​
EDS self-induction
τ
=
L
R
\tau = \frac{L}{R}
τ
=
R
L
​
Time scale of RL chains
Review of the situation
The spark on the inductive load switch is caused by the large EDS when the current is rapidly reduced.
04
Links and application
In the real world
The spark on the inductive load switch is caused by the large EDS when the current is rapidly reduced.
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 "Samoinization" through the model, not just the formula.
Outcome 2
Identify and correctly use terms: self-induction, inductiveness, transition.
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.
self-induction
The emergence of EDI in a chain when it changes its own current and magnetic flow.
Inductiveness
The coefficient of communication between the current in the contour and the current adhesion generated by it.
transition process
Temporary change of currents and voltages between fixed states of the electrical circuit.
RL chain
An electrical chain with resistance and inductiveness, the current of which does not change instantaneously during switching.
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.
E
s
=
−
L
Δ
I
Δ
t
\mathcal{E}_s=-L\frac{\Delta I}{\Delta t}
E
s
​
=
−
L
Δ
t
Δ
I
​
model effect
Eds self-induction.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
N
Φ
=
L
I
N\Phi=LI
N
Φ
=
L
I
For a linear coil, the current is proportional to current; the L coefficient is called inductivity.
E
s
=
−
Δ
(
N
Φ
)
Δ
t
\mathcal{E}_s=-\frac{\Delta(N\Phi)}{\Delta t}
E
s
​
=
−
Δ
t
Δ
(
N
Φ
)
​
The Faraday Act applies to changing the coil's own flow.
E
s
=
−
L
Δ
I
Δ
t
\mathcal{E}_s=-L\frac{\Delta I}{\Delta t}
E
s
​
=
−
L
Δ
t
Δ
I
​
At constant L, the change in flow of adhesion is L ΔI.
Conditions:
Linear coil with constant inductivity L; mean value per Δt. If the heart is soaked L depends on I.
Monitoring:
The dimensions of both parts shall coincide; the result shall be checked for sign, order and limit case.
τ
=
L
R
\tau = \frac{L}{R}
τ
=
R
L
​
model effect
Time scale rl chain.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
L
d
I
d
t
+
R
I
=
E
L\frac{dI}{dt}+RI=\mathcal{E}
L
d
t
d
I
​
+
R
I
=
E
For a sequenced RL chain, the stress rule takes into account the fall of RI and EDS self-induction.
I
(
t
)
=
I
∞
(
1
−
e
−
R
t
/
L
)
I(t)=I_\infty\left(1-e^{-Rt/L}\right)
I
(
t
)
=
I
∞
​
(
1
−
e
−
Rt
/
L
)
The decision on the permanent EDS describes the exponential increase in current.
e
−
R
t
/
L
=
e
−
t
/
τ
⇒
τ
=
L
R
e^{-Rt/L}=e^{-t/\tau}\quad\Rightarrow\quad\tau=\frac{L}{R}
e
−
Rt
/
L
=
e
−
t
/
τ
⇒
τ
=
R
L
​
The comparison of indicators determines the characteristic time of the process.
Conditions:
Consequent linear RL chain with constant L and total R connected to a constant source; transition processes without changing parameters.
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
You can't put the formula on any situation just because it's a coincidence of letters. The key condition of this subject is that the current through the coil cannot change with a leap in the perfect model.
How to Check the Mind
The inductivity slows the current growth when shut down. Then check the unit, vector direction and result behaviour at zero or very large parameter.
Σ
Conclusion on the topic
Self-induction
The current change in the circuit changes its own magnetic flow and creates an EDS that prevents it. Induction depends on geometry and the heart.
The current through the coil can't change with a leap in the perfect model.
When closed, inductiveness slows the current growth, keeping it open.
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.