Full electrical circuit

Содержание и основные понятия

The source divides the charges at the expense of the external forces; the EDS equals their operation on a single charge, and internal resistance causes the voltage to drop inside the source.
GEF · 10 grade
PIF · Baseline
Interactive model
EDS
internal resistance
complete chain
short circuit
01
The physical picture
What happens and what boundaries the model has.
Main message
The source divides the charges at the expense of the external forces; the EDS equals their operation on a single charge, and internal resistance causes the voltage to drop inside the source.
The current depends on the amount of external and internal resistance.
The voltage at the terminals of the operating source is less than the EDS when the current is applied.
The short circuit is limited almost exclusively to internal resistance and dangerously large currents.
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.
I
=
E
R
+
r
I=\frac{\mathcal E}{R+r}
I
=
R
+
r
E
​
Oma law for the complete chain
U
=
E
−
I
r
U=\mathcal E-Ir
U
=
E
−
I
r
voltage at terminals
Review of the situation
A source with EDS 12 V and r = 1 om connected to R = 5 om creates current 2 A and a terminals voltage of 10 V.
04
Links and application
In the real world
A source with EDS 12 V and r = 1 om connected to R = 5 om creates current 2 A and a terminals voltage of 10 V.
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 whole electrical circuit through the model, not just through the formula.
Outcome 2
Distinguish and correctly use terms: EDS, internal resistance, complete chain.
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.
EDS
Work of the external forces inside the source on a single carry-over charge.
internal resistance
Resistance to the movement of the charge inside the current source.
complete chain
Locked electrical circuit comprising external load and internal part of the source.
short circuit
Combining chain points with very low resistance, causing a sharp increase in current.
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.
I
=
E
R
+
r
I=\frac{\mathcal E}{R+r}
I
=
R
+
r
E
​
model effect
The laws of the Oma are for the complete chain.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
E
=
U
R
+
U
r
\mathcal E=U_R+U_r
E
=
U
R
​
+
U
r
​
The source ' s EDS is spent on external and internal resistance voltage drops.
U
R
=
I
R
,
U
r
=
I
r
U_R=IR,\quad U_r=Ir
U
R
​
=
I
R
,
U
r
​
=
I
r
The Oma Act applies to each oxy section.
E
=
I
(
R
+
r
)
⇒
I
=
E
R
+
r
\mathcal E=I(R+r)\quad\Rightarrow\quad I=\frac{\mathcal E}{R+r}
E
=
I
(
R
+
r
)
⇒
I
=
R
+
r
E
​
The summation of the falls and the division into total resistance give the current.
Conditions:
Closed chain with permanent EDS source and permanent internal resistance; external load omatic, transition processes are missing.
Monitoring:
The dimensions of both parts shall coincide; the result shall be checked for sign, order and limit case.
U
=
E
−
I
r
U=\mathcal E-Ir
U
=
E
−
I
r
model effect
The tension on the terminals.
The following is an indication of the definition, experience or law from which this entry arises and where it is applicable.
E
=
I
R
+
I
r
\mathcal E=IR+Ir
E
=
I
R
+
I
r
In the complete EDS chain, the sum of the voltage falls on the external and internal resistance.
U
=
I
R
U=IR
U
=
I
R
The voltage at the terminals of the active source is equal to that at the external load.
U
=
E
−
I
r
U=\mathcal E-Ir
U
=
E
−
I
r
Ir's internal fall is subtracted from the EDS.
Conditions:
The source gives current I to the external omestic chain and has a constant internal resistance r; when charging the source, the label agreement changes.
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 the tok depends on the amount of external and internal resistance.
How to Check the Mind
The voltage at the terminals of the active source is less than the EDS at current response. Then check the units, vector direction and result behaviour at zero or very large parameter.
Equation system for a complex chain
The Oma Act for the complete chain works for the same circuit. On a network with multiple sources and branches, the currents are selected, the knots rule I = 0 is applied and the contour rule x -IR = 0. The negative current found means that the actual direction is opposite to that chosen.
Σ
Conclusion on the topic
Full electrical circuit
The source divides the charges at the expense of the external forces; the EDS equals their operation on a single charge, and internal resistance causes the voltage to drop inside the source.
The current depends on the amount of external and internal resistance.
The voltage at the terminals of the operating source is less than the EDS when the current is applied.
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.