Ohm's Law with Python

Introduction

As I studied Python, I realized that it would be easy to calculate complex numbers, so I tried to see if Ohm's law used in electrical engineering could be implemented really easily in Python.

Ohm's law (direct current)

It is one of the most important laws in electrical engineering and is the first formula to learn.

V = IR

• $ V $: Voltage, $ I $: Current, $ R $: Resistor The above Ohm's law is written in Python. Set to calculate for the parameter entered empty among $ V $, $ I $, and $ R $.

Ohm'sLawDC.py

# V = IR for DC circuit
print('Empty a parameter to calculate')

V = float(input('Input V : ') or 0)
I = float(input('Input I : ') or 0)
R = float(input('Input R : ') or 0)

if not V:
    V = R * I
elif not I:
    I = V / R
elif not R:
    R = V / I
else:
    print('Empty a parameter to calculate')

print('V =', V, '[V]')
print('I =', I, '[A]')
print('R =', R, '[Ω]')

This is the first input part, but it is assumed that the parameters entered empty will be calculated. Therefore, if you convert the input as it is as shown below, an error will occur at the time of conversion with the parameter of empty input.

V = float(input('Input V : '))

Therefore, I wrote that after inputting with str type once, it is converted only when the input is not empty. I really wish I could have a simpler notation ... I checked the initial value of input and whether it can be set, but I could not find such an argument orz

2019/11/10 postscript I was told in the comments that the following notation can be used. By doing this, I was able to convert it to a number without an if statement. it's amazing!

V = float(input('Input V : ') or 0)

The or operator actually judges the value on the left side as true or false and returns the result. Deep, I see ... https://docs.python.org/ja/3/library/stdtypes.html#boolean-operations-and-or-not

The result is output as follows.

Empty a parameter to calculate
Input V : 100
Input I : 
Input R : 50
V = 100.0 [V]
I = 2.0 [A]
R = 50.0 [Ω]

Ohm's law (exchange)

This is the main subject of this time. I didn't use complex numbers at all for direct current, but for alternating current, I need to calculate complex numbers with impedance (Z) added.

v = iz

• $ V $: Voltage, $ i $: Current, $ z $: Impedance

z = \sqrt{(r^2+x^2)}

• $ R $: Resistance, $ x $: Reactance

The difference from direct current is that ** $ x $ (reactance) ** is added to the parameters. This reactance represents the imaginary component in the AC circuit.

Now, let's write Ohm's law in an AC circuit in Python. Make sure to calculate for the empty parameter of $ v $, $ i $, $ r $, $ x $.

Ohm'sLawAC.py

# v = iz for AC circuit

print('Empty a parameter to calculate')

v = complex(input('Input v[V] : ') or 0)
i = complex(input('Input i[A] : ') or 0)
r = complex(input('Input r[Ω] : ') or 0)
x = complex(input('Input x[jΩ] : ') or 0)*1j

if not v:
    z = (r ** 2 + (x / 1j) ** 2) ** (1/2)
    v = z * i
elif not i:
    z = (r ** 2 + (x / 1j) ** 2) ** (1/2)
    i = v / z
elif not r:
    z = v / i
    r = (z ** 2 - (x / 1j) ** 2) ** (1/2)
elif not x:
    z = v / i
    x = (z ** 2 - r ** 2) ** (1/2) *1j
else:
    print('Empty a parameter to calculate')

print('v =', v, '[V]')
print('i =', i, '[A]')
print('r =', r, '[Ω]')
print('x =', x, '[jΩ]')
print('z =', z, '[Ω]')

Surprisingly, it was difficult to input real numbers and internally convert real numbers to complex numbers. It's easy as long as you know that you can convert real numbers to imaginary numbers with "* 1j".

The result is output as follows.

Empty a parameter to calculate
Input v[V] : 10
Input i[A] : 2
Input r[Ω] : 3
Input x[jΩ] : 
v = (10+0j) [V]
i = (2+0j) [A]
r = (3+0j) [Ω]
x = 4j [jΩ]
z = (5+0j) [Ω]

Ohm's law could definitely be calculated using complex numbers. There were occasional trips such as the input / output part and the conversion method from real numbers to complex numbers, but if you know how to write imaginary numbers in Python, the rest will work as long as you write the calculation formula obediently, so there is almost no problem. was. I think it was really easy.

After all you are amazing! Python-kun!