I think when the bears try to eat the bacon or hotdogs or whatever you hang it gives them a shock. I guess bears have really thick fur and the nose and mouth are the best place to shock them. I will ask my friend for more details though because I am not sure.
Yup. From some decades of experience with electric fences, animals have to be trained to the fence. In other words, make sure they get a good jolt on purpose. Otherwise, if they are running along and get run into the fence by mistake, they might bolt...through the fence and into (or out of) the enclosure! Then not be able to figure out how to get out, now that they know what the fence means.
Bacon is a great idea, since the bear will be very focused on the food and what it is hanging on, and will be VERY clear on where the shock came from.
When I was a kid we would train unshod animals to the fence by using and antique calf collar (metal) with a bit of chain hanging from it. This pretty much guaranteed good contact and conduction. Wet grass made it even better. Then tempt the animal to the fence with food.