dna - Should the length of the electrodes in the electrophoresis chamber be proportional to chamber's size?

I am trying to build a small horizontal electrophoresis chamber from scratch. I want to use it for comet assay and I will be using only 1 slide, so it's going to be about 3cm wide, 10cm long and 4cm high, just enough to fit the slide and a small amount of buffer. As far as I know such thing is not commercially available, so before I make it I want to make sure that it's going to work. The main issue is the cost of the electrode (has to be platinum wire). I don't want to spent that much money just to realize that it doesn't work.
My question is: is a 3cm electrode in a 60-70cm³ enough? Basically, are there any physical restrictions on the size and the position of the electrodes and the shape of the chamber?
Since I am a biologist and my knowledge in physics are quite limited, I would greatly appreciate any information about this.