please give me example of isolated system.. need this in my physics..?
That would be a huge waste of money and effort. Lunch is such a minor part of a child's diet that it is mostly meaningless and it is lack of exercise which is the key problem. Eat enough of anything and sit around all day watching TV and playing vid games and you'll get fat. Eat the so called worst foods and exercise all day and you'll be healthy long as you get sufficient vites. Quit blaming the food when it's a cultural problem not the food's fault. We need a culture where it's safe for kids to be outside getting exercise, where parents have enough time off work to actually parent their kids. A culture which espouses moderation in things like TV and Vid games.
Electricity will always try to find the easiest path, or path of least resistance, to the ground. The wires attract because air is not a particularly good conductor but copper is a great conductor. The lightning doesn't have to build up as much to make the jump to the wire as a jump to the ground.
