splice one wire slightly longer

Found a splice where 3 wires meet. One wire is slightly longer than the others but only by 3mm or so.
Easy solution is to trim it but I was just wondering if there are any dangers in having a wire like this in a wire nut with others? Is there any arc danger or will the electricity always just go through the easiets path at the join of the other wires in the splice nut?

 

As long as the wires are in a box and accessible, Wires connected with a wire nut are ok.

 

Ideally you would want the same length. With more experience, it will just come to you.
When connecting a stranded wire to solid wire, you want stranded to be a little longer.

 

Out of interest, is there any chance that the electricity could arc form a bit of wire.
Take an exaggerated example where you have 2 copper wires with no sheath and you place them together over a 10cm length but close together but only touching right at the end.

 

10cm is almost 4 Inches. This isn't going to happen. I know you said it's exaggerated, but still...
Based on viewing all your posts, you are doing quite a bit of electric work on your home.
All you need to do is make sure your connections are secure.
Strip wires and group them together, apply wire nut and tighten securely. Tug on wires individually after applying wire nut to check for any loose wires, this is more important when tying wires of different gauges together.
Electricity can arc from loose connections. But you are gaining experience and this should not be an issue.

 

One way of splicing I was taught in the Navy, to keep the thickness of the entire cable manageable was to stagger the soldered connections by a few inches. That way you didn't have a big bulge right in one spot. Electrically, it makes no difference. In house wiring, you could have 3 connections w/o an issue as long as they were in a box.

 

If one wire sticks out past the other two just trim the ends so they are even.