There are quite a few "demonstrations of Ki" available on YouTube which I personally find embarrassing in the extreme. I won't link to them because I don't want to give them any more publicity than they already have. Suffice to say, that some people's understanding of Ki in Aikido is very different from mine. It was a joy, then, to discover this short, simple, down-to-earth explanation of Ki Aikido by Kashiwaya Sensei, Chief Instructor of the Ki Society in the USA.
Kashiwaya Sensei is not only a very skilled practitioner of Aikido but he also has a rare quality of being able to convey his joy and enthusiasm for the art. He gives a simple, level-headed explanation of the four principles of Ki Aikido in this video. He also makes what I consider to be a crucial point - that Aikido techniques are not useful to most people once they leave the dojo. But the core teachings of Ki Aikido ("mind/body coordination") are valuable in daily life. Anyway, here's the video. I hope you find it of interest.