Could someone please explain to me how an electrical mains-tester works, the sort where you touch a live wire with a screwdriver-type tip and a bulb lights up when you push a button with your thumb.
Presumably the current flows in one direction, namely from the cable to the tip. And you are earthed. So why doesn't it try to complete a circuit by going through you? And the bulb surely hasn't got an enormous resistance?
What am I missing?
Thanks for any enlightenment here!
Harry