# Computing resistor power dissipation in Python using UliEngineering

In this example we’ll calculate the power dissipation of a 1 kΩ resistor with a constant current of 30 mA flowing through it, using our science and engineering Python library UliEngineering.

In order to install UliEngineering (a Python3-only library), run

`sudo pip3 install -U UliEngineering`

Now we can compute the resistor power dissipation using `power_dissipated_in_resistor_by_current()`

```from UliEngineering.EngineerIO import auto_print
from UliEngineering.Electronics.Resistors import *
# Just compute the value:
power = power_dissipated_in_resistor_by_current("1 kΩ", "30 mA") # power = 0.9

# Print value: prints: prints "900 mW"
auto_print(power_dissipated_in_resistor_by_current, "1 kΩ", "30 mA")```

Since the result is `900 mW`, you can deduce that you need to use a resistor with a power rating of at least one Watt.

Note that you can pass both numbers (like `0.03`) or strings (like `30 mA` or `0.03 A`) to most UliEngineering functions. SI prefixes like `k` and `M` are automatically decoded

If you know the voltage across the resistor, you can use `power_dissipated_in_resistor_by_voltage()`. Let’s assume there is `1V` dropped across the resistor:

```from UliEngineering.EngineerIO import auto_print
from UliEngineering.Electronics.Resistors import *
# Just compute the value:
power = power_dissipated_in_resistor_by_voltage("1 kΩ", "30 mA") # power = 0.001

# Print value: prints: prints "1.00 mW"
auto_print(power_dissipated_in_resistor_by_voltage, "1 kΩ", "30 mA")```

So in this case the power dissipation is extremely low – only `1.00 mW` – and won’t matter for most practical applications.

In many cases, you can also pass NumPy arrays to UliEngineering functions:

```from UliEngineering.EngineerIO import format_value
from UliEngineering.Electronics.Resistors import *
import numpy as np

# Compute the value:
resistors = np.asarray([100, 500, 1000]) # 100 Ω, 500 Ω, 1 kΩ
power = power_dissipated_in_resistor_by_voltage(resistors, "30 mA") # power = 0.001

# power = [9.0e-06 1.8e-06 9.0e-07]``` 