lee writes: > But how do know that there is voltage when you cannot measure it or > otherwise make evident that there is? As far as I understand it, you > cannot do that without current flowing. You can do it for water pressure > without water flowing, but I don't see how you could do it for voltage > without flow.
You could use a potentiometer (not the kind you are used to: <http://en.wikipedia.org/wiki/Potentiometer_(measuring_instrument)>) or you could measure the force exerted on a capacitor plate. Both these methods are used in standards work. Usually, though, you would just use a voltmeter with an input impedence larger that the leakage-resistance of the wires connecting it to the source. -- John Hasler -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]