magnitude and luminosity...?

Question

how can you tell the luminosity by knowing the magnitude of a star?

ex. A star with a magnitude of -5 and a temp of 24000 degrees C would be found in what category of the HR diagram?

Answer 1

You need both the magnitude, (apparent brightness),
and the distance to calculate luminosity.
In your example, the temp. is the key info.
It gives the 'color`. Find that on the diagram.