dc-electricity 0.2.9

dcelectricity package

The aim of this project is to understand the rudiments of DC electrical circuits and their functioning (primary and secondary school curricula).

Prerequisites

Python : version 3
All operating systems

Installing dcelectricity python package

From Pypi repository :
https://pypi.org/project/dc-electricity

pip install dc-electricity

Basic electrical quantities

• Voltage (volt)
• Current (ampere)
• Resistance (ohm)
• Conductance (siemens)
• Power (watt)
• Energy (joule / kWh)

Electrical laws

• Kirchhoff’s current law
• Kirchhoff’s voltage law
• Ohm's law
• Resistors in series and parallel
• Voltage divider and current divider
• Millman's theorem
• Joule's first law (P=I²R=V²/R)
• Power law (P=VI)
• Energy formula (P=E/t)

DC Circuit diagram

Circuit should only contain :

• independent voltage source
• independent current source
• resistors

A complete example

            V1
        <---------
         +------+
   --->--| R1   |--------+-------+
     I1  +------+        |       |
 ^                    I2 v       v I3
 |                       |       |      ^
 |                     +---+   +---+    |
 |                     |   |   |   |    |
E|                     |R2 |   |R3 |    | V2
 |                     |   |   |   |    |
 |                     +---+   +---+    |
 |                       |       |
                         |       |
   ----------------------+-------+

Datas :
E = 12 V ; R1 = 1 kΩ ; R2 = 2.7 kΩ ; R3 = 1.8 kΩ
What are the I1, I2, I3 currents ?
What are the V1, V2 voltages ?

>>> from dcelectricity.dc_en import *  # english version
>>> # from dcelectricity.dc_fr import *  # french version
>>> E = Voltage(12)
>>> E
Voltage : 12.000000 V
>>> R1 = Resistor(1, 'k')
>>> R1
Resistance : 1000 Ω (1.000000 kΩ)
>>> R2 = Resistor(2.7, 'k')
>>> R3 = Resistor(1.8, 'k')
>>> R23 = R2//R3  # resistances in parallel
>>> R23
Resistance : 1080 Ω (1.080000 kΩ)
>>> Req = R1 + R23  # resistances in series
>>> Req
Resistance : 2080 Ω (2.080000 kΩ)
>>> I1 = E/Req  # Ohm's law
>>> I1
Current : 0.00576923 A (5.769231 mA)
>>> V1 = I1*R1  # Ohm's law
>>> V1
Voltage : 5.769231 V
>>> V2 = E - V1  # Kirchhoff’s voltage law
>>> V2
Voltage : 6.230769 V
>>> I2 = V2/R2  # Ohm's law
>>> I2
Current : 0.00230769 A (2.307692 mA)
>>> I3 = I1 - I2  # Kirchhoff’s current law
>>> I3
Current : 0.00346154 A (3.461538 mA)

Resistances and conductances

>>> G2 = 1/R2
>>> G2
Conductance : 0.00037037 S (370.370370 µS)
>>> G3 = 1/R3
>>> 1/(G2+G3)
Resistance : 1080 Ω (1.080000 kΩ)
>>> R2*(R3/(R2+R3))
Resistance : 1080 Ω (1.080000 kΩ)
>>> 1/(1/R2 + 1/R3)
Resistance : 1080 Ω (1.080000 kΩ)

Law class

>>> law = Law()
>>> # voltage divider
>>> V2 = law.VoltageDivider(vtotal=E, r=R2//R3, r2=R1)
>>> V2
Voltage : 6.230769 V
>>> # Millman's theorem
>>> gnd = Voltage(0)
>>> V2 = law.Millman(v_r=[(E, R1), (gnd, R2), (gnd, R3)])
>>> V2
Voltage : 6.230769 V
>>> (E/R1)/(1/R1 + 1/R2 + 1/R3)
Voltage : 6.230769 V
>>> V2/E
0.5192307692307693
>>> # current divider
>>> I3 = law.CurrentDivider(itotal=I1, r=R3, r2=R2)
>>> I3
Current : 0.00346154 A (3.461538 mA)
>>> I1*R2/(R2+R3)
Current : 0.00346154 A (3.461538 mA)

Electrical power, Joule's first law

>>> P = E*I1  # source power
>>> P
Power : 0.0692308 W (69.230769 mW)
>>> P1 = law.Joule(r=R1, i=I1)
>>> P1
Power : 0.033284 W (33.284024 mW)
>>> R1*I1*I1
Power : 0.033284 W (33.284024 mW)
>>> law.Joule(r=R1, v=V1)
Power : 0.033284 W (33.284024 mW)
>>> V1*(V1/R1)
Power : 0.033284 W (33.284024 mW)
>>> P2 = law.Joule(r=R2, i=I2)
>>> P2
Power : 0.0143787 W (14.378698 mW)
>>> P3 = law.Joule(r=R3, i=I3)
Power : 0.021568 W (21.568047 mW)
>>> P1+P2+P3
Power : 0.0692308 W (69.230769 mW)

Energy and power

>>> T = Time(1800)  # or T = Time(0.5, 'h')
>>> P = Power(1500)
>>> E = P*T  # or E = law.Energy(t=T, p=P)
>>> E
Energy : 2.7e+06 J (2.700000 MJ) 0.75 kWh
>>> E/P
Time : 1800 s (1.800000 ks) 0.5 h
>>> E/T
Power : 1500 W (1.500000 kW)

Advantages and limitations

This module manages basic arithmetic operations + - * / as well as // which designates two resistors in parallel.

The dimensional homogeneity is checked :

>>> V3 = V1 - V2 + I3  # V+A -> Error
TypeError
>>> I = I1 + 0.5  # A+number -> Error
TypeError
>>> I2 = Current(0.5)
>>> I = I1 + I2
>>> I = 5*I2 - V1/R1 + I3

The result of an operation must give a quantity whose unit is one of : V, A, Ω, S, W, J, s, no unit (ratio).
Otherwise, you will get an error :

>>> R1/V1  # Ω/V -> 1/A -> Error
TypeError
>>> R2*(R3/(R2+R3))  # Ω*(Ω/Ω) -> Ω*() -> Ω
>>> R2*R3/(R2+R3)  # Ω*Ω -> Error
TypeError
>>> P = V1*(V1/R1)  # V*(V/Ω) -> V*A -> W
>>> P = V1*V1/R1    # V*V -> Error
TypeError
>>> V1()**2/R1()

See also

http://fsincere.free.fr/isn/python/cours_python_dc.php

https://pypi.org/project/ac-electricity