Electric arc: How to calculate the required voltage for a light bow?

[Hans42]

<Moderator's note: Moved from a homework forum.>

Calculate the required voltage to produce a electric arc between 2 iron nails (distance: 3cm).

I´ve read in the internet that you need 1 kV per mm. But how can I calculate this value, that I need 1kV per 1mm?

 

[berkeman]

<Moderator's note: Moved from a homework forum.>

Calculate the required voltage to produce a electric arc between 2 iron nails (distance: 3cm).

I´ve read in the internet that you need 1 kV per mm. But how can I calculate this value, that I need 1kV per 1mm?

Welcome to the PF.

See if this helps: https://en.wikipedia.org/wiki/Paschen's_law

What is your background in working with high voltages?